,transcriber's ,note3 ,italics are enclosed in underscores4 ,additional notes will be found near the end of this ebook4 ,,philosophy ,,philosophy ,by ,bertrand ,russell ,illustration ,,new ,,york ,w ,w ,,norton ,,company1 ,,inc4 ,publishers ,copyright1 #aibg1 ,,bertrand ,,russell ,published in ,great ,britain under the title 8,an ,outline of ,philosophy0 ,,printed ,,in ,,the ,,united ,,states ,,of ,,america ,,for ,,the ,,publishers ,,by ,,the ,,van ,,rees ,,press ,,contents ,,chapter ,,page ,i4 ,,philosophic ,,doubts #a ,,part ,i ,,man ,,from ,,without ,,ii4 ,,man ,,and ,,his ,,environment #af ,,iii4 ,,the ,,process ,,of ,,learning ,,in ,,animals ,,and ,,infants #bi ,,iv4 ,,language #dc ,v4 ,,perception ,,objectively ,,regarded #eh ,,vi4 ,,memory ,,objectively ,,regarded #gj ,,vii4 ,,inference ,,as ,a ,,habit #gi ,,viii4 ,,knowledge ,,behaviouristically ,,considered #hh ,,part ,,ii ,,the ,,physical ,,world ,,ix4 ,,the ,,structure ,,of ,,the ,,atom #ig ,x4 ,,relativity #ajg ,,xi4 ,,causal ,,laws ,,in ,,physics #aad ,,xii4 ,,physics ,,and ,,perception #abc ,,xiii4 ,,physical ,,and ,,perceptual ,,space #acg ,,xiv4 ,,perception ,,and ,,physical ,,causal ,,laws #add ,,xv4 ,,the ,,nature ,,of ,,our ,,knowledge ,,of ,,physics #aea ,,part ,,iii ,,man ,,from ,,within ,,xvi4 ,,self-,,observation #afa ,,xvii4 ,,images #agf ,,xviii4 ,,imagination ,,and ,,memory #ahg ,,xix4 ,,the ,,introspective ,,analysis ,,of ,,perception #bja ,,xx4 ,,consciousness8 #baj ,,xxi4 ,,emotion1 ,,desire1 ,,and ,,will #bah ,,xxii4 ,,ethics #bbe ,,part ,,iv ,,the ,,universe ,,xxiii4 ,,some ,,great ,,philosophies ,,of ,,the ,,past #bcf ,,xxiv4 ,,truth ,,and ,,falsehood #bed ,,xxv4 ,,the ,,validity ,,of ,,inference #bff ,,xxvi4 ,,events1 ,,matter1 ,,and ,,mind #bgf ,,xxvii4 ,,man',s ,,place ,,in ,,the ,,universe #bib ,,philosophy ,,chapter ,i ,,philosophic ,,doubts ,perhaps it might be expected that ,i should begin with a definition of 8philosophy01 but1 rightly or wrongly1 ,i do not propose to do so4 ,the definition of 8philosophy0 will vary according to the philosophy we adopt2 all that we can say to begin with is that there are certain problems1 which certain people find interesting1 and which do not1 at least at present1 belong to any of the special sciences4 ,these problems are all such as to raise doubts concerning what commonly passes for knowledge2 and if the doubts are to be answered1 it can only be by means of a special study1 to which we give the name 8philosophy04 ,therefore the first step in defining 8philosophy0 is the indication of these problems and doubts1 which is also the first step in the actual study of philosophy4 ,there are some among the traditional problems of philosophy that do not seem to me to lend themselves to intellectual treatment1 because they transcend our cognitive powers2 such problems ,i shall not deal with4 ,there are others1 however1 as to which1 even if a final solution is not possible at present1 yet much can be done to show the direction in which a solution is to be sought1 and the kind of solution that may in time prove possible4 ,philosophy arises from an unusually obstinate attempt to arrive at real knowledge4 ,what passes for knowledge in ordinary life suffers from three defects3 it is cocksure1 vague1 and self-contradictory4 ,the first step towards philosophy consists in becoming aware of these defects1 not in order to rest content with a lazy scepticism1 but in order to substitute an amended kind of knowledge which shall be tentative1 precise1 and self-consistent4 ,there is of course another quality which we wish our knowledge to possess1 namely comprehensiveness3 we wish the area of our knowledge to be as wide as possible4 ,but this is the business of science rather than of philosophy4 ,a man does not necessarily become a better philosopher through knowing more scientific facts2 it is principles and methods and general conceptions that he should learn from science if philosophy is what interests him4 ,the philosopher's work is1 so to speak1 at the second remove from crude fact4 ,science tries to collect facts into bundles by means of scientific laws2 these laws1 rather than the original facts1 are the raw material of philosophy4 ,philosophy involves a criticism of scientific knowledge1 not from a point of view ultimately different from that of science1 but from a point of view less concerned with details and more concerned with the harmony of the whole body of special sciences4 ,the special sciences have all grown up by the use of notions derived from common sense1 such as things and their qualities1 space1 time1 and causation4 ,science itself has shown that none of these common-sense notions will quite serve for the explanation of the world2 but it is hardly the province of any special science to undertake the necessary reconstruction of fundamentals4 ,this must be the business of philosophy4 ,i want to say1 to begin with1 that ,i believe it to be a business of very great importance4 ,i believe that the philosophical errors in common-sense beliefs not only produce confusion in science1 but also do harm in ethics and politics1 in social institutions1 and in the conduct of everyday life4 ,it will be no part of my business1 in this volume1 to point out these practical effects of a bad philosophy3 my business will be purely intellectual4 ,but if ,i am right1 the intellectual adventures which lie before us have effects in many directions which seem1 at first sight1 quite remote from our theme4 ,the effect of our passions upon our beliefs forms a favourite subject of modern psychologists2 but the converse effect1 that of our beliefs upon our passions1 also exists1 though it is not such as an old-fashioned intellectualist psychology would have supposed4 ,although ,i shall not discuss it1 we shall do well to bear it in mind1 in order to realise that our discussions may have bearings upon matters lying outside the sphere of pure intellect4 ,i mentioned a moment ago three defects in common beliefs1 namely1 that they are cocksure1 vague1 and self-contradictory4 ,it is the business of philosophy to correct these defects so far as it can1 without throwing over knowledge altogether4 ,to be a good philosopher1 a man must have a strong desire to know1 combined with great caution in believing that he knows2 he must also have logical acumen and the habit of exact thinking4 ,all these1 of course1 are a matter of degree4 ,vagueness1 in particular1 belongs1 in some degree1 to all human thinking2 we can diminish it indefinitely1 but we can never abolish it wholly4 ,philosophy1 accordingly1 is a continuing activity1 not something in which we can achieve final perfection once for all4 ,in this respect1 philosophy has suffered from its association with theology4 ,theological dogmas are fixed1 and are regarded by the orthodox as incapable of improvement4 ,philosophers have too often tried to produce similarly final systems3 they have not been content with the gradual approximations that satisfied men of science4 ,in this they seem to me to have been mistaken4 ,philosophy should be piecemeal and provisional like science2 final truth belongs to heaven1 not to this world4 ,the three defects which ,i have mentioned are interconnected1 and by becoming aware of any one we may be led to recognise the other two4 ,i will illustrate all three by a few examples4 ,let us take first the belief in common objects1 such as tables and chairs and trees4 ,we all feel quite sure about these in ordinary life1 and yet our reasons for confidence are really very inadequate4 ,naive common sense supposes that they are what they appear to be1 but that is impossible1 since they do not appear exactly alike to any two simultaneous observers2 at least1 it is impossible if the object is a single thing1 the same for all observers4 ,if we are going to admit that the object is not what we see1 we can no longer feel the same assurance that there is an object2 this is the first intrusion of doubt4 ,however1 we shall speedily recover from this set-back1 and say that of course the object is 8really0 what physics says it is4#a ,now physics says that a table or a chair is 8really0 an incredibly vast system of electrons and protons in rapid motion1 with empty space in between4 ,this is all very well4 ,but the physicist1 like the ordinary man1 is dependent upon his senses for the existence of the physical world4 ,if you go up to him solemnly and say1 8would you be so kind as to tell me1 as a physicist1 what a chair really is01 you will get a learned answer4 ,but if you say1 without preamble3 8,is there a chair there80 he will say3 8,of course there is2 can't you see it80 ,to this you ought to reply in the negative4 ,you ought to say1 8,no1 ,i see certain patches of colour1 but ,i don't see any electrons or protons1 and you tell me that they are what a chair consists of04 ,he may reply3 8,yes1 but a large number of electrons and protons close together look like a patch of colour04 ,what do you mean by 8look like08 you will then ask4 ,he is ready with an answer4 ,he means that light-waves start from the electrons and protons 7or1 more probably1 are reflected by them from a source of light71 reach the eye1 have a series of effects upon the rods and cones1 the optic nerve1 and the brain1 and finally produce a sensation4 ,but he has never seen an eye or an optic nerve or a brain1 any more than he has seen a chair2 he has only seen patches of colour which1 he says1 are what eyes 8look like40 ,that is to say1 he thinks that the sensation you have when 7as you think7 you see a chair1 has a series of causes1 physical and psychological1 but all of them1 on his own showing1 lie essentially and forever outside experience4 ,nevertheless1 he pretends to base his science upon observation4 ,obviously there is here a problem for the logician1 a problem belonging not to physics1 but to quite another kind of study4 ,this is a first example of the way in which the pursuit of precision destroys certainty4 #a ,i am not thinking here of the elementary physics to be found in a school text-book2 ,i am thinking of modern theoretical physics1 more particularly as regards the structure of atoms1 as to which ,i shall have more to say in later chapters4 ,the physicist believes that he infers his electrons and protons from what he perceives4 ,but the inference is never clearly set forth in a logical chain1 and1 if it were1 it might not look sufficiently plausible to warrant much confidence4 ,in actual fact1 the whole development from common-sense objects to electrons and protons has been governed by certain beliefs1 seldom conscious1 but existing in every natural man4 ,these beliefs are not unalterable1 but they grow and develop like a tree4 ,we start by thinking that a chair is as it appears to be1 and is still there when we are not looking4 ,but we find1 by a little reflection1 that these two beliefs are incompatible4 ,if the chair is to persist independently of being seen by us1 it must be something other than the patch of colour we see1 because this is found to depend upon conditions extraneous to the chair1 such as how the light falls1 whether we are wearing blue spectacles1 and so on4 ,this forces the man of science to regard the 8real0 chair as the cause 7or an indispensable part of the cause7 of our sensations when we see the chair4 ,thus we are committed to causation as an a priori belief without which we should have no reason for supposing that there is a 8real0 chair at all4 ,also1 for the sake of permanence we bring in the notion of substance3 the 8real0 chair is a substance1 or collection of substances1 possessed of permanence and the power to cause sensations4 ,this metaphysical belief has operated1 more or less unconsciously1 in the inference from sensations to electrons and protons4 ,the philosopher must drag such beliefs into the light of day1 and see whether they still survive4 ,often it will be found that they die on exposure4 ,let us now take up another point4 ,the evidence for a physical law1 or for any scientific law1 always involves both memory and testimony4 ,we have to rely both upon what we remember to have observed on former occasions1 and on what others say they have observed4 ,in the very beginnings of science1 it may have been possible sometimes to dispense with testimony2 but very soon every scientific investigation began to be built upon previously ascertained results1 and thus to depend upon what others had recorded4 ,in fact1 without the corroboration of testimony we should hardly have had much confidence in the existence of physical objects4 ,sometimes people suffer from hallucinations1 that is to say1 they think they perceive physical objects1 but are not confirmed in this belief by the testimony of others4 ,in such cases1 we decide that they are mistaken4 ,it is the similarity between the perceptions of different people in similar situations that makes us feel confident of the external causation of our perceptions2 but for this1 whatever naive beliefs we might have had in physical objects would have been dissipated long ago4 ,thus memory and testimony are essential to science4 ,nevertheless1 each of these is open to criticism by the sceptic4 ,even if we succeed1 more or less1 in meeting his criticism1 we shall1 if we are rational1 be left with a less complete confidence in our original beliefs than we had before4 ,once more1 we shall become less cocksure as we become more accurate4 ,both memory and testimony lead us into the sphere of psychology4 ,i shall not at this stage discuss either beyond the point at which it is clear that there are genuine philosophical problems to be solved4 ,i shall begin with memory4 ,memory is a word which has a variety of meanings4 ,the kind that ,i am concerned with at the moment is the recollection of past occurrences4 ,this is so notoriously fallible that every experimenter makes a record of the result of his experiment at the earliest possible moment3 he considers the inference from written words to past events less likely to be mistaken than the direct beliefs which constitute memory4 ,but some time1 though perhaps only a few seconds1 must elapse between the observation and the making of the record1 unless the record is so fragmentary that memory is needed to interpret it4 ,thus we do not escape from the need of trusting memory to some degree4 ,moreover1 without memory we should not think of interpreting records as applying to the past1 because we should not know that there was any past4 ,now1 apart from arguments as to the proved fallibility of memory1 there is one awkward consideration which the sceptic may urge4 ,remembering1 which occurs now1 cannot possibly--he may say--prove that what is remembered occurred at some other time1 because the world might have sprung into being five minutes ago1 exactly as it then was1 full of acts of remembering which were entirely misleading4 ,opponents of ,darwin1 such as ,edmund ,gosse's father1 urged a very similar argument against evolution4 ,the world1 they said1 was created in #djjd ,b4,c41 complete with fossils1 which were inserted to try our faith4 ,the world was created suddenly1 but was made such as it would have been if it had evolved4 ,there is no logical impossibility about this view4 ,and similarly there is no logical impossibility in the view that the world was created five minutes ago1 complete with memories and records4 ,this may seem an improbable hypothesis1 but it is not logically refutable4 ,apart from this argument1 which may be thought fantastic1 there are reasons of detail for being more or less distrustful of memory4 ,it is obvious that no direct confirmation of a belief about a past occurrence is possible1 because we cannot make the past recur4 ,we can find confirmation of an indirect kind in the revelations of others and in contemporary records4 ,the latter1 as we have seen1 involve some degree of memory1 but they may involve very little1 for instance when a shorthand report of a conversation or speech has been made at the time4 ,but even then1 we do not escape wholly from the need of memory extending over a longer stretch of time4 ,suppose a wholly imaginary conversation were produced for some criminal purpose1 we should depend upon the memories of witnesses to establish its fictitious character in a law-court4 ,and all memory which extends over a long period of time is very apt to be mistaken2 this is shown by the errors invariably found in autobiographies4 ,any man who comes across letters which he wrote many years ago can verify the manner in which his memory has falsified past events4 ,for these reasons1 the fact that we cannot free ourselves from dependence upon memory in building up knowledge is1 prima facie1 a reason for regarding what passes for knowledge as not quite certain4 ,the whole of this subject of memory will be considered more carefully in later chapters4 ,testimony raises even more awkward problems4 ,what makes them so awkward is the fact that testimony is involved in building up our knowledge of physics1 and that1 conversely1 physics is required in establishing the trustworthiness of testimony4 ,moreover1 testimony raises all the problems connected with the relation of mind and matter4 ,some eminent philosophers1 e4g4 ,leibniz1 have constructed systems according to which there would be no such thing as testimony1 and yet have accepted as true many things which cannot be known without it4 ,i do not think philosophy has quite done justice to this problem1 but a few words will1 ,i think1 show its gravity4 ,for our purposes1 we may define testimony as noises heard1 or shapes seen1 analogous to those which we should make if we wished to convey an assertion1 and believed by the hearer or seer to be due to someone else's desire to convey an assertion4 ,let us take a concrete instance3 ,i ask a policeman the way1 and he says1 8,fourth turn to the right1 third to the left40 ,that is to say1 ,i hear these sounds1 and perhaps ,i see what ,i interpret as his lips moving4 ,i assume that he has a mind more or less like my own1 and has uttered these sounds with the same intention as ,i should have had if ,i had uttered them1 namely to convey information4 ,in ordinary life1 all this is not1 in any proper sense1 an inference2 it is a belief which arises in us on the appropriate occasion4 ,but if we are challenged1 we have to substitute inference for spontaneous belief1 and the more the inference is examined the more shaky it looks4 ,the inference that has to be made has two steps1 one physical and one psychological4 ,the physical inference is of the sort we considered a moment ago1 in which we pass from a sensation to a physical occurrence4 ,we hear noises1 and think they proceed from the policeman's body4 ,we see moving shapes1 and interpret them as physical motions of his lips4 ,this inference1 as we saw earlier1 is in part justified by testimony2 yet now we find that it has to be made before we can have reason to believe that there is any such thing as testimony4 ,and this inference is certainly sometimes mistaken4 ,lunatics hear voices which other people do not hear2 instead of crediting them with abnormally acute hearing1 we lock them up4 ,but if we sometimes hear sentences which have not proceeded from a body1 why should this not always be the case8 ,perhaps our imagination has conjured up all the things that we think others have said to us4 ,but this is part of the general problem of inferring physical objects from sensations1 which1 difficult as it is1 is not the most difficult part of the logical puzzles concerning testimony4 ,the most difficult part is the inference from the policeman's body to his mind4 ,i do not mean any special insult to policemen2 ,i would say the same of politicians and even of philosophers4 ,the inference to the policeman's mind certainly may be wrong4 ,it is clear that a maker of wax-works could make a life-like policeman and put a gramophone inside him1 which would cause him periodically to tell visitors the way to the most interesting part of the exhibition at the entrance to which he would stand4 ,they would have just the sort of evidence of his being alive that is found convincing in the case of other policemen4 ,descartes believed that animals have no minds1 but are merely complicated automata4 ,eighteenth-century materialists extended this doctrine to men4 ,but ,i am not now concerned with materialism2 my problem is a different one4 ,even a materialist must admit that1 when he talks1 he means to convey something1 that is to say1 he uses words as signs1 not as mere noises4 ,it may be difficult to decide exactly what is meant by this statement1 but it is clear that it means something1 and that it is true of one's own remarks4 ,the question is3 ,are we sure that it is true of the remarks we hear1 as well as of those we make8 ,or are the remarks we hear perhaps just like other noises1 merely meaningless disturbances of the air8 ,the chief argument against this is analogy3 the remarks we hear are so like those we make that we think they must have similar causes4 ,but although we cannot dispense with analogy as a form of inference1 it is by no means demonstrative1 and not infrequently leads us astray4 ,we are therefore left1 once more1 with a prima facie reason for uncertainty and doubt4 ,this question of what we mean ourselves when we speak brings me to another problem1 that of introspection4 ,many philosophers have held that introspection gave the most indubitable of all knowledge2 others have held that there is no such thing as introspection4 ,descartes1 after trying to doubt everything1 arrived at 8,i think1 therefore ,i am01 as a basis for the rest of knowledge4 ,dr4 ,john ,b4 ,watson the behaviourist holds1 on the contrary1 that we do not think1 but only talk4 ,dr4 ,watson1 in real life1 gives as much evidence of thinking as anyone does1 so if he is not convinced that he thinks1 we are all in a bad way4 ,at any rate1 the mere existence of such an opinion as his1 on the part of a competent philosopher1 must suffice to show that introspection is not so certain as some people have thought4 ,but let us examine this question a little more closely4 ,the difference between introspection and what we call perception of external objects seems to me to be connected1 not with what is primary in our knowledge1 but with what is inferred4 ,we think1 at one time1 that we are seeing a chair2 at another1 that we are thinking about philosophy4 ,the first we call perception of an external object2 the second we call introspection4 ,now we have already found reason to doubt external perception1 in the full-blooded sense in which common-sense accepts it4 ,i shall consider later what there is that is indubitable and primitive in perception2 for the moment1 ,i shall anticipate by saying that what is indubitable in 8seeing a chair0 is the occurrence of a certain pattern of colours4 ,but this occurrence1 we shall find1 is connected with me just as much as with the chair2 no one except myself can see exactly the pattern that ,i see4 ,there is thus something subjective and private about what we take to be external perception1 but this is concealed by precarious extensions into the physical world4 ,i think introspection1 on the contrary1 involves precarious extensions into the mental world3 shorn of these1 it is not very different from external perception shorn of its extensions4 ,to make this clear1 ,i shall try to show what we know to be occurring when1 as we say1 we think about philosophy4 ,suppose1 as the result of introspection1 you arrive at a belief which you express in the words3 8,i am now believing that mind is different from matter04 ,what do you know1 apart from inferences1 in such a case8 ,first of all1 you must cut out the word 8,i03 the person who believes is an inference1 not part of what you know immediately4 ,in the second place1 you must be careful about the word 8believing03 ,i am not now concerned with what this word should mean in logic or theory of knowledge2 ,i am concerned with what it can mean when used to describe a direct experience4 ,in such a case1 it would seem that it can only describe a certain kind of feeling4 ,and as for the proposition you think you are believing1 namely1 8mind is different from matter01 it is very difficult to say what is really occurring when you think you believe it4 ,it may be mere words1 pronounced1 visualised1 or in auditory or motor images4 ,it may be images of what the words 8mean01 but in that case it will not be at all an accurate representation of the logical content of the proposition4 ,you may have an image of a statue of ,newton 8voyaging through strange seas of thought alone01 and another image of a stone rolling downhill1 combined with the words 8how different60 ,or you may think of the difference between composing a lecture and eating your dinner4 ,it is only when you come to expressing your thought in words that you approach logical precision4 ,both in introspection and in external perception1 we try to express what we know in ,,words4 ,we come here1 as in the question of testimony1 upon the social aspect of knowledge4 ,the purpose of words is to give the same kind of publicity to thought as is claimed for physical objects4 ,a number of people can hear a spoken word or see a written word1 because each is a physical occurrence4 ,if ,i say to you1 8mind is different from matter01 there may be only a very slight resemblance between the thought that ,i am trying to express and the thought which is aroused in you1 but these two thoughts have just this in common1 that they can be expressed by the same words4 ,similarly1 there may be great differences between what you and ,i see when1 as we say1 we look at the same chair2 nevertheless we can both express our perceptions by the same words4 ,a thought and a perception are thus not so very different in their own nature4 ,if physics is true1 they are different in their correlations3 when ,i see a chair1 others have more or less similar perceptions1 and it is thought that these are all connected with light-waves coming from the chair1 whereas1 when ,i think a thought1 others may not be thinking anything similar4 ,but this applies also to feeling a toothache1 which would not usually be regarded as a case of introspection4 ,on the whole1 therefore1 there seems no reason to regard introspection as a different kind of knowledge from external perception4 ,but this whole question will concern us again at a later stage4 ,as for the trustworthiness of introspection1 there is again a complete parallelism with the case of external perception4 ,the actual datum1 in each case1 is unimpeachable1 but the extensions which we make instinctively are questionable4 ,instead of saying1 8,i am believing that mind is different from matter01 you ought to say1 8certain images are occurring in a certain relation to each other1 accompanied by a certain feeling04 ,no words exist for describing the actual occurrence in all its particularity2 all words1 even proper names1 are general1 with the possible exception of 8this01 which is ambiguous4 ,when you translate the occurrence into words1 you are making generalisations and inferences1 just as you are when you say 8there is a chair04 ,there is really no vital difference between the two cases4 ,in each case1 what is really a datum is unutterable1 and what can be put into words involves inferences which may be mistaken4 ,when ,i say that 8inferences0 are involved1 ,i am saying something not quite accurate unless carefully interpreted4 ,in 8seeing a chair01 for instance1 we do not first apprehend a coloured pattern1 and then proceed to infer a chair3 belief in the chair arises spontaneously when we see the coloured pattern4 ,but this belief has causes not only in the present physical stimulus1 but also partly in past experience1 partly in reflexes4 ,in animals1 reflexes play a very large part2 in human beings1 experience is more important4 ,the infant learns slowly to correlate touch and sight1 and to expect others to see what he sees4 ,the habits which are thus formed are essential to our adult notion of an object such as a chair4 ,the perception of a chair by means of sight has a physical stimulus which affects only sight directly1 but stimulates ideas of solidity and so on through early experience4 ,the inference might be called 8physiological04 ,an inference of this sort is evidence of past correlations1 for instance between touch and sight1 but may be mistaken in the present instance2 you may1 for instance1 mistake a reflection in a large mirror for another room4 ,similarly in dreams we make mistaken physiological inferences4 ,we cannot therefore feel certainty in regard to things which are in this sense inferred1 because1 when we try to accept as many of them as possible1 we are nevertheless compelled to reject some for the sake of self-consistency4 ,we arrived a moment ago at what we called 8physiological inference0 as an essential ingredient in the common-sense notion of a physical object4 ,physiological inference1 in its simplest form1 means this3 given a stimulus ,s1 to which1 by a reflex1 we react by a bodily movement ,r1 and a stimulus ,s with a reaction ,r1 if the two stimuli are frequently experienced together1 ,s will in time produce ,r4#b ,that is to say1 the body will act as if ,s were present4 ,physiological inference is important in theory of knowledge1 and ,i shall have much to say about it at a later stage4 ,for the present1 ,i have mentioned it partly to prevent it from being confused with logical inference1 and partly in order to introduce the problem of induction1 about which we must say a few preliminary words at this stage4 #b ,e4g4 if you hear a sharp noise and see a bright light simultaneously often1 in time the noise without the light will cause your pupils to contract4 ,induction raises perhaps the most difficult problem in the whole theory of knowledge4 ,every scientific law is established by its means1 and yet it is difficult to see why we should believe it to be a valid logical process4 ,induction1 in its bare essence1 consists of the argument that1 because ,a and ,b have been often found together and never found apart1 therefore1 when ,a is found again1 ,b will probably also be found4 ,this exists first as a 8physiological inference01 and as such is practised by animals4 ,when we first begin to reflect1 we find ourselves making inductions in the physiological sense1 for instance1 expecting the food we see to have a certain kind of taste4 ,often we only become aware of this expectation through having it disappointed1 for instance if we take salt thinking it is sugar4 ,when mankind took to science1 they tried to formulate logical principles justifying this kind of inference4 ,i shall discuss these attempts in later chapters2 for the present1 ,i will only say that they seem to me very unsuccessful4 ,i am convinced that induction must have validity of some kind in some degree1 but the problem of showing how or why it can be valid remains unsolved4 ,until it is solved1 the rational man will doubt whether his food will nourish him1 and whether the sun will rise tomorrow4 ,i am not a rational man in this sense1 but for the moment ,i shall pretend to be4 ,and even if we cannot be completely rational1 we should probably all be the better for becoming somewhat more rational than we are4 ,at the lowest estimate1 it will be an interesting adventure to see whither reason will lead us4 ,the problems we have been raising are none of them new1 but they suffice to show that our everyday views of the world and of our relations to it are unsatisfactory4 ,we have been asking whether we know this or that1 but we have not yet asked what 8knowing0 is4 ,perhaps we shall find that we have had wrong ideas as to knowing1 and that our difficulties grow less when we have more correct ideas on this point4 ,i think we shall do well to begin our philosophical journey by an attempt to understand knowing considered as part of the relation of man to his environment1 forgetting1 for the moment1 the fundamental doubts with which we have been concerned4 ,perhaps modern science may enable us to see philosophical problems in a new light4 ,in that hope1 let us examine the relation of man to his environment with a view to arriving at a scientific view as to what constitutes knowledge4 ,,part ,i ,,man ,,from ,,without ,,chapter ,,ii ,,man ,,and ,,his ,,environment ,if our scientific knowledge were full and complete1 we should understand ourselves and the world and our relation to the world4 ,as it is1 our understanding of all three is fragmentary4 ,for the present1 it is the third question1 that of our relation to the world1 that ,i wish to consider1 because this brings us nearest to the problems of philosophy4 ,we shall find that it will lead us back to the other two questions1 as to the world and as to ourselves1 but that we shall understand both these better if we have considered first how the world acts upon us and how we act upon the world4 ,there are a number of sciences which deal with ,man4 ,we may deal with him in natural history1 as one among the animals1 having a certain place in evolution1 and related to other animals in ascertainable ways4 ,we may deal with him in physiology1 as a structure capable of performing certain functions1 and reacting to the environment in ways of which some1 at least1 can be explained by chemistry4 ,we may study him in sociology1 as a unit in various organisms1 such as the family and the state4 ,and we may study him1 in psychology1 as he appears to himself4 ,this last gives what we may call an internal view of man1 as opposed to the other three1 which give an external view4 ,that is to say1 in psychology we use data which can only be obtained when the observer and the observed are the same person1 whereas in the other ways of studying ,man all our data can be obtained by observing other people4 ,there are different ways of interpreting this distinction1 and different views of its importance1 but there can be no doubt that there is such a distinction4 ,we can remember our own dreams1 whereas we cannot know the dreams of others unless they tell us about them4 ,we know when we have toothache1 when our food tastes too salty1 when we are remembering some past occurrence1 and so on4 ,all these events in our lives other people cannot know in the same direct way4 ,in this sense1 we all have an inner life1 open to our own inspection but to no one else's4 ,this is no doubt the source of the traditional distinction of mind and body3 the body was supposed to be that part of us which others could observe1 and the mind that part which was private to ourselves4 ,the importance of the distinction has been called in question in recent times1 and ,i do not myself believe that it has any fundamental philosophical significance4 ,but historically it has played a dominant part in determining the conceptions from which men set out when they began to philosophise1 and on this account1 if on no other1 it deserves to be borne in mind4 ,knowledge1 traditionally1 has been viewed from within1 as something which we observe in ourselves rather than as something which we can see others displaying4 ,when ,i say that it has been so viewed1 ,i mean that this has been the practice of philosophers2 in ordinary life1 people have been more objective4 ,in ordinary life1 knowledge is something which can be tested by examinations1 that is to say1 it consists in a certain kind of response to a certain kind of stimulus4 ,this objective way of viewing knowledge is1 to my mind1 much more fruitful than the way which has been customary in philosophy4 ,i mean that1 if we wish to give a definition of 8knowing01 we ought to define it as a manner of reacting to the environment1 not as involving something 7a 8state of mind07 which only the person who has the knowledge can observe4 ,it is because ,i hold this view that ,i think it best to begin with ,man and his environment1 rather than with those matters in which the observer and the observed must be the same person4 ,knowing1 as ,i view it1 is a characteristic which may be displayed in our reactions to our environment2 it is therefore necessary first of all to consider the nature of these reactions as they appear in science4 ,let us take some everyday situation4 ,suppose you are watching a race1 and at the appropriate moment you say1 8they're off04 ,this exclamation is a reaction to the environment1 and is taken to show knowledge if it is made at the same time as others make it4 ,now let us consider what has been really happening1 according to science4 ,the complication of what has happened is almost incredible4 ,it may conveniently be divided into four stages3 first1 what happened in the outside world between the runners and your eyes2 secondly1 what happened in your body from your eyes to your brain2 thirdly1 what happened in your brain2 fourthly1 what happened in your body from your brain to the movements of your throat and tongue which constituted your exclamation4 ,of these four stages1 the first belongs to physics1 and is dealt with in the main by the theory of light2 the second and fourth belong to physiology2 the third1 though it should theoretically also belong to physiology1 belongs in fact rather to psychology1 owing to our lack of knowledge as to the brain4 ,the third stage embodies the results of experience and learning4 ,it is responsible for the fact that you speak1 which an animal would not do1 and that you speak ,english1 which a ,frenchman would not do4 ,this immensely complicated occurrence is1 nevertheless1 about the simplest example of knowledge that could possibly be given4 ,for the moment1 let us leave on one side the part of this process which happens in the outside world and belongs to physics4 ,i shall have much to say about it later1 but what has to be said is not altogether easy1 and we will take less abstruse matters first4 ,i will merely observe that the event which we are said to perceive1 namely the runners starting1 is separated by a longer or shorter chain of events from the event which happens at the surface of our eyes4 ,it is this last that is what is called the 8stimulus04 ,thus the event that we are said to perceive when we see is not the stimulus1 but an anterior event related to it in a way that requires investigation4 ,the same applies to hearing and smell1 but not to touch or to perception of states of our own body4 ,in these cases1 the first of the above four stages is absent4 ,it is clear that1 in the case of sight1 hearing and smell1 there must be a certain relation between the stimulus and the event said to be perceived1 but we will not now consider what this relation must be4 ,we will consider1 rather1 the second1 third1 and fourth stages in an act of perceptive knowledge4 ,this is the more legitimate as these stages always exist1 whereas the first is confined to certain senses4 ,the second stage is that which proceeds from the sense-organ to the brain4 ,it is not necessary for our purposes to consider exactly what goes on during this journey4 ,a purely physical event--the stimulus--happens at the boundary of the body1 and has a series of effects which travel along the afferent nerves to the brain4 ,if the stimulus is light1 it must fall on the eye to produce the characteristic effects2 no doubt light falling on other parts of the body has effects1 but they are not those that distinguish vision4 ,similarly1 if the stimulus is sound1 it must fall on the ear4 ,a sense-organ1 like a photographic plate1 is responsive to stimuli of a certain sort3 light falling on the eye has effects which are different for different wave-lengths1 intensities1 and directions4 ,when the events in the eye due to incident light have taken place1 they are followed by events in the optic nerve1 leading at last to some occurrence in the brain--an occurrence which varies with the stimulus4 ,the occurrence in the brain must be different for different stimuli in all cases where we can perceive differences4 ,red and yellow1 for instance1 are distinguishable in perception2 therefore the occurrences along the optic nerve and in the brain must have a different character when caused by red light from what they have when caused by yellow light4 ,but when two shades of colour are so similar that they can only be distinguished by delicate instruments1 not by perception1 we cannot be sure that they cause occurrences of different characters in the optic nerve and brain4 ,when the disturbance has reached the brain1 it may or may not cause a characteristic set of events in the brain4 ,if it does not1 we shall not be what is called 8conscious0 of it4 ,for to be 8conscious0 of seeing yellow1 whatever else it may be1 must certainly involve some kind of cerebral reaction to the message brought by the optic nerve4 ,it may be assumed that the great majority of messages brought to the brain by the afferent nerves never secure any attention at all--they are like letters to a government office which remain unanswered4 ,the things in the margin of the field of vision1 unless they are in some way interesting1 are usually unnoticed2 if they are noticed1 they are brought into the centre of the field of vision unless we make a deliberate effort to prevent this from occurring4 ,these things are visible1 in the sense that we could be aware of them if we chose1 without any change in our physical environment or in our sense-organs2 that is to say1 only a cerebral change is required to enable them to cause a reaction4 ,but usually they do not provoke any reaction2 life would be altogether too wearing if we had to be always reacting to everything in the field of vision4 ,where there is no reaction1 the second stage completes the process1 and the third and fourth stages do not arise4 ,in that case1 there has been nothing that could be called 8perception0 connected with the stimulus in question4 ,to us1 however1 the interesting case is that in which the process continues4 ,in this case there is first a process in the brain1 of which the nature is as yet conjectural1 which travels from the centre appropriate to the sense in question to a motor centre4 ,from these there is a process which travels along an efferent nerve1 and finally results in a muscular event causing some bodily movement4 ,in our illustration of the man watching the beginning of a race1 a process travels from the part of the brain concerned with sight to the part concerned with speech2 this is what we called the third stage4 ,then a process travels along the efferent nerves and brings about the movements which constitute saying 8they're off02 this is what we called the fourth stage4 ,unless all four stages exist1 there is nothing that can be called 8knowledge04 ,and even when they are all present1 various further conditions must be satisfied if there is to be 8knowledge04 ,but these observations are premature1 and we must return to the analysis of our third and fourth stages4 ,the third stage is of two sorts1 according as we are concerned with a reflex or with a 8learned reaction01 as ,dr4 ,watson calls it4 ,in the case of a reflex1 if it is complete at birth1 a new-born infant or animal has a brain so constituted that1 without the need of any previous experience1 there is a connection between a certain process in the afferent nerves and a certain other process in the efferent nerves4 ,a good example of a reflex is sneezing4 ,a certain kind of tickling in the nose produces a fairly violent movement having a very definite character1 and this connection exists already in the youngest infants4 ,learned reactions1 on the other hand1 are such as only occur because of the effect of previous occurrences in the brain4 ,one might illustrate by an analogy which1 however1 would be misleading if pressed4 ,imagine a desert in which no rain has ever fallen1 and suppose that at last a thunderstorm occurs in it2 then the course taken by the water will correspond to a reflex4 ,but if rain continues to fall frequently1 it will form watercourses and river valleys2 when this has occurred1 the water runs away along pre-formed channels1 which are attributable to the past 8experience0 of the region4 ,this corresponds to 8learned reactions04 ,one of the most notable examples of learned reactions is speech3 we speak because we have learned a certain language1 not because our brain had originally any tendency to react in just that way4 ,perhaps all knowledge1 certainly nearly all1 is dependent upon learned reactions1 i4e41 upon connections in the brain which are not part of man's congenital equipment but are the result of events which have happened to him4 ,to distinguish between learned and unlearned responses is not always an easy task4 ,it cannot be assumed that responses which are absent during the first weeks of life are all learned4 ,to take the most obvious instance2 sexual responses change their character to a greater or less extent at puberty1 as a result of changes in the ductless glands1 not as a result of experience4 ,but this instance does not stand alone3 as the body grows and develops1 new modes of response come into play1 modified1 no doubt1 by experience1 but not wholly due to it4 ,for example3 a new-born baby cannot run1 and therefore does not run away from what is terrifying1 as an older child does4 ,the older child has learned to run1 but has not necessarily learned to run away2 the stimulus in learning to run may have never been a terrifying object4 ,it would therefore be a fallacy to suppose that we can distinguish between learned and unlearned responses by observing what a new-born infant does1 since reflexes may come into play at a later stage4 ,conversely1 some things which a child does at birth may have been learned1 when they are such as it could have done in the womb--for example1 a certain amount of kicking and stretching4 ,the whole distinction between learned and unlearned responses1 therefore1 is not so definite as we could wish4 ,at the two extremes we get clear cases1 such as sneezing on the one hand and speaking on the other2 but there are intermediate forms of behaviour which are more difficult to classify4 ,this is not denied even by those who attach most importance to the distinction between learned and unlearned responses4 ,in ,dr4 ,watson's ,behaviorism 7p4 #ajc7 there is a 8,summary of ,unlearned ,equipment01 which ends with the following paragraph3 8,other activities appear at a later stage--such as blinking1 reaching1 handling1 handedness1 crawling1 standing1 sitting-up1 walking1 running1 jumping4 ,in the great majority of these later activities it is difficult to say how much of the act as a whole is due to training or conditioning4 ,a considerable part is unquestionably due to the growth changes in structure1 and the remainder is due to training and conditioning40 7,watson's italics47 ,it is not possible to make a logically sharp distinction in this matter2 in certain cases we have to be satisfied with something less exact4 ,for example1 we might say that those developments which are merely due to normal growth are to count as unlearned1 while those which depend upon special circumstances in the individual biography are to count as learned4 ,but take1 say1 muscular development3 this will not take place normally unless the muscles are used1 and if they are used they are bound to learn some of the skill which is appropriate to them4 ,and some things which must certainly count as learned1 such as focussing with the eyes1 depend upon circumstances which are normal and must be present in the case of every child who is not blind4 ,the whole distinction1 therefore1 is one of degree rather than of kind2 nevertheless it is valuable4 ,the value of the distinction between learned and unlearned reactions is connected with the laws of learning1 to which we shall come in the next chapter4 ,experience modifies behaviour according to certain laws1 and we may say that a learned reaction is one in the formation of which these laws have played a part4 ,for example3 children are frightened of loud noises from birth1 but are not at first frightened of dogs2 after they have heard a dog barking loudly1 they may become frightened of dogs1 which is a learned reaction4 ,if we knew enough about the brain1 we could make the distinction precise1 by saying that learned reactions are those depending upon modifications of the brain other than mere growth4 ,but as it is1 we have to judge by observations of bodily behaviour1 and the accompanying modifications in the brain are assumed on a basis of theory rather than actually observed4 ,the essential points1 for our purposes1 are comparatively simple4 ,man or any other animal1 at birth1 is such as to respond to certain stimuli in certain specific ways1 i4e4 by certain kinds of bodily movements2 as he grows1 these ways of responding change1 partly as the mere result of developing structure1 partly in consequence of events in his biography4 ,the latter influence proceeds according to certain laws1 which we shall consider1 since they have much to do with the genesis of 8knowledge04 ,but--the indignant reader may be exclaiming--knowing something is not a bodily movement1 but a state of mind1 and yet you talk to us about sneezing and such matters4 ,i must ask the indignant reader's patience4 ,he 8knows0 that he has states of mind1 and that his knowing is itself a state of mind4 ,i do not deny that he has states of mind1 but ,i ask two questions3 ,first1 what sort of thing are they8 ,secondly1 what evidence can he give me that he knows about them8 ,the first question he may find very difficult2 and if he wants1 in his answer1 to show that states of mind are something of a sort totally different from bodily movements1 he will have to tell me also what bodily movements are1 which will plunge him into the most abstruse part of physics4 ,all this ,i propose to consider later on1 and then ,i hope the indignant reader will be appeased4 ,as to the second question1 namely1 what evidence of his knowledge another man can give me1 it is clear that he must depend upon speech or writing1 i4e4 in either case upon bodily movements4 ,therefore whatever knowledge may be to the knower1 as a social phenomenon it is something displayed in bodily movements4 ,for the present ,i am deliberately postponing the question of what knowledge is to the knower1 and confining myself to what it is for the external observer4 ,and for him1 necessarily1 it is something shown by bodily movements made in answer to stimuli--more specifically1 to examination questions4 ,what else it may be ,i shall consider at a later stage4 ,however we may subsequently add to our present account by considering how knowledge appears to the knower1 that will not invalidate anything that we may arrive at by considering how knowledge appears to the external observer4 ,and there is something which it is important to realise1 namely1 that we are concerned with a process in which the environment first acts upon a man1 and then he reacts upon the environment4 ,this process has to be considered as a whole if we are to discuss what knowledge is4 ,the older view would have been that the effect of the environment upon us might constitute a certain kind of knowledge 7perception71 while our reaction to the environment constituted volition4 ,these were1 in each case1 8mental0 occurrences1 and their connection with nerves and brain remained entirely mysterious4 ,i think the mystery can be eliminated1 and the subject removed from the realm of guesswork1 by starting with the whole cycle from stimulus to bodily movement4 ,in this way1 knowing becomes something active1 not something contemplative4 ,knowing and willing1 in fact1 are merely aspects of the one cycle1 which must be considered in its entirety if it is to be rightly understood4 ,a few words must be said about the human body as a mechanism4 ,it is an inconceivably complicated mechanism1 and some men of science think that it is not explicable in terms of physics and chemistry1 but is regulated by some 8vital principle0 which makes its laws different from those of dead matter4 ,these men are called 8vitalists04 ,i do not myself see any reason to accept their view1 but at the same time our knowledge is not sufficient to enable us to reject it definitely4 ,what we can say is that their case is not proved1 and that the opposite view is1 scientifically1 a more fruitful working hypothesis4 ,it is better to look for physical and chemical explanations where we can1 since we know of many processes in the human body which can be accounted for in this way1 and of none which certainly cannot4 ,to invoke a 8vital principle0 is to give an excuse for laziness1 when perhaps more diligent research would have enabled us to do without it4 ,i shall therefore assume1 as a working hypothesis1 that the human body acts according to the same laws of physics and chemistry as those which govern dead matter1 and that it differs from dead matter1 not by its laws1 but by the extraordinary complexity of its structure4 ,the movements of the human body may1 none the less1 be divided into two classes1 which we may call respectively 8mechanical0 and 8vital04 ,as an example of the former1 ,i should give the movement of a man falling from a cliff into the sea4 ,to explain this1 in its broad features1 it is not necessary to take account of the fact that the man is alive2 his centre of gravity moves exactly as that of a stone would move4 ,but when a man climbs up a cliff1 he does something that dead matter of the same shape and weight would never do2 this is a 8vital0 movement4 ,there is in the human body a lot of stored chemical energy in more or less unstable equilibrium2 a very small stimulus can release this energy1 and cause a considerable amount of bodily movement4 ,the situation is analogous to that of a large rock delicately balanced on the top of a conical mountain2 a tiny shove may send it thundering down into the valley1 in one direction or another according to the direction of the shove4 ,so if you say to a man 8your house is on fire01 he will start running2 although the stimulus contained very little energy1 his expenditure of energy may be tremendous4 ,he increases the available energy by panting1 which makes his body burn up faster and increases the energy due to combustion2 this is just like opening the draft in a furnace4 8,vital0 movements are those that use up this energy which is in unstable equilibrium4 ,it is they alone that concern the bio-chemist1 the physiologist1 and the psychologist4 ,the others1 being just like the movements of dead matter1 may be ignored when we are specially concerned with the study of ,man4 ,vital movements have a stimulus which may be inside or outside the body1 or both at once4 ,hunger is a stimulus inside the body1 but hunger combined with the sight of good food is a double stimulus1 both internal and external4 ,the effect of a stimulus may be1 in theory1 according to the laws of physics and chemistry1 but in most cases this is1 at present1 no more than a pious opinion4 ,what we know from observation is that behaviour is modified by experience1 that is to say1 that if similar stimuli are repeated at intervals they produce gradually changing reactions4 ,when a bus conductor says1 8,fares1 please01 a very young child has no reaction1 an older child gradually learns to look for pennies1 and1 if a male1 ultimately acquires the power of producing the requisite sum on demand without conscious effort4 ,the way in which our reactions change with experience is a distinctive characteristic of animals2 moreover it is more marked in the higher than in the lower animals1 and most marked of all in ,man4 ,it is a matter intimately connected with 8intelligence01 and must be investigated before we can understand what constitutes knowledge from the standpoint of the external observer2 we shall be concerned with it at length in the next chapter4 ,speaking broadly1 the actions of all living things are such as tend to biological survival1 i4e4 to the leaving of a numerous progeny4 ,but when we descend to the lowest organisms1 which have hardly anything that can be called individuality1 and reproduce themselves by fission1 it is possible to take a simpler view4 ,living matter1 within limits1 has the chemical peculiarity of being self-perpetuating1 and of conferring its own chemical composition upon other matter composed of the right elements4 ,one spore falling into a stagnant pond may produce millions of minute vegetable organisms2 these1 in turn1 enable one small animal to have myriads of descendants living on the small plants2 these1 in turn1 provide life for larger animals1 newts1 tadpoles1 fishes1 etc4 ,in the end there is enormously more protoplasm in that region than there was to begin with4 ,this is no doubt explicable as a result of the chemical constitution of living matter4 ,but this purely chemical self-preservation and collective growth is at the bottom of everything else that characterises the behaviour of living things4 ,every living thing is a sort of imperialist1 seeking to transform as much as possible of its environment into itself and its seed4 ,the distinction between self and posterity is one which does not exist in a developed form in asexual unicellular organisms2 many things1 even in human life1 can only be completely understood by forgetting it4 ,we may regard the whole of evolution as flowing from this 8chemical imperialism0 of living matter4 ,of this1 ,man is only the last example 7so far74 ,he transforms the surface of the globe by irrigation1 cultivation1 mining1 quarrying1 making canals and railways1 breeding certain animals1 and destroying others2 and when we ask ourselves1 from the standpoint of an outside observer1 what is the end achieved by all these activities1 we find that it can be summed up in one very simple formula3 to transform as much as possible of the matter on the earth's surface into human bodies4 ,domestication of animals1 agriculture1 commerce1 industrialism have been stages in this process4 ,when we compare the human population of the globe with that of other large animals and also with that of former times1 we see that 8chemical imperialism0 has been1 in fact1 the main end to which human intelligence has been devoted4 ,perhaps intelligence is reaching the point where it can conceive worthier ends1 concerned with the quality rather than the quantity of human life4 ,but as yet such intelligence is confined to minorities1 and does not control the great movements of human affairs4 ,whether this will ever be changed ,i do not venture to predict4 ,and in pursuing the simple purpose of maximising the amount of human life1 we have at any rate the consolation of feeling at one with the whole movement of living things from their earliest origin on this planet4 ,,chapter ,,iii ,,the ,,process ,,of ,,learning ,,in ,,animals ,,and ,,infants ,in the present chapter ,i wish to consider the processes by which1 and the laws according to which1 an animal's original repertoire of reflexes is changed into a quite different set of habits as a result of events that happen to it4 ,a dog learns to follow his master in preference to anyone else2 a horse learns to know his own stall in the stable2 a cow learns to come to the cow-shed at milking time4 ,all these are acquired habits1 not reflexes2 they depend upon the circumstances of the animals concerned1 not merely upon the congenital characteristics of the species4 ,when ,i speak of an animal 8learning0 something1 ,i shall include all cases of acquired habits1 whether or not they are useful to the animal4 ,i have known horses in ,italy 8learn0 to drink wine1 which ,i cannot believe to have been a desirable habit4 ,a dog may 8learn0 to fly at a man who has ill-treated it1 and may do so with such regularity and ferocity as to lead to its being killed4 ,i do not use learning in any sense involving praise1 but merely to denote modification of behaviour as the result of experience4 ,the manner in which animals learn has been much studied in recent years1 with a great deal of patient observation and experiment4 ,certain results have been obtained as regards the kinds of problems that have been investigated1 but on general principles there is still much controversy4 ,one may say broadly that all the animals that have been carefully observed have behaved so as to confirm the philosophy in which the observer believed before his observations began4 ,nay1 more1 they have all displayed the national characteristics of the observer4 ,animals studied by ,americans rush about frantically1 with an incredible display of hustle and pep1 and at last achieve the desired result by chance4 ,animals observed by ,germans sit still and think1 and at last evolve the solution out of their inner consciousness4 ,to the plain man1 such as the present writer1 this situation is discouraging4 ,i observe1 however1 that the type of problem which a man naturally sets to an animal depends upon his own philosophy1 and that this probably accounts for the differences in the results4 ,the animal responds to one type of problem in one way and to another in another2 therefore the results obtained by different investigators1 though different1 are not incompatible4 ,but it remains necessary to remember that no one investigator is to be trusted to give a survey of the whole field4 ,the matters with which we shall be concerned in this chapter belong to behaviourist psychology1 and in part to pure physiology4 ,nevertheless1 they seem to me vital to a proper understanding of philosophy1 since they are necessary for an objective study of knowledge and inference4 ,i mean by an 8objective0 study one in which the observer and the observed need not be the same person2 when they must be identical1 ,i call the study 8subjective40 ,for the present we are concerned with what is required for understanding 8knowledge0 as an objective phenomenon4 ,we shall take up the question of the subjective study of knowledge at a later stage4 ,the scientific study of learning in animals is a very recent growth2 it may almost be regarded as beginning with ,thorndike's ,animal ,intelligence1 which was published in #aiaa4 ,thorndike invented the method which has been adopted by practically all subsequent ,american investigators4 ,in this method an animal is separated from food1 which he can see or smell1 by an obstacle which he may overcome by chance4 ,a cat1 say1 is put in a cage having a door with a handle which he may by chance push open with his nose4 ,at first the cat makes entirely random movements1 until he gets his result by a mere fluke4 ,on the second occasion1 in the same cage1 he still makes some random movements1 but not so many as on the first occasion4 ,on the third occasion he does still better1 and before long he makes no useless movements4 ,nowadays it has become customary to employ rats instead of cats1 and to put them in a model of the ,hampton ,court maze rather than in a cage4 ,they take all sorts of wrong turnings at first1 but after a time they learn to run straight out without making any mistake4 ,dr4 ,watson gives averages for nineteen rats1 each of which was put into the maze repeatedly1 with food outside where the rat could smell it4 ,in all the experiments care was taken to make sure that the animal was very hungry4 ,dr4 ,watson says3 8,the first trial required on the average over seventeen minutes4 ,during this time the rat was running around the maze1 into blind alleys1 running back to the starting point1 starting for the food again1 biting at the wires around him1 scratching himself1 smelling this spot and that on the floor4 ,finally he got to the food4 ,he was allowed only a bite4 ,again he was put back into the maze4 ,the taste of the food made him almost frantic in his activity4 ,he dashed about more rapidly4 ,the average time for the group on the second trial is only a little over seven minutes2 on the fourth trial not quite three minutes2 from this point to the twenty-third trial the improvement is very gradual40 ,on the thirtieth trial the time required1 on the average1 was about thirty seconds4#c ,this set of experiments may be taken as typical of the whole group of studies to which it belongs4 #c ,watson1 ,behaviorism1 pp4 #afi-gj4 ,thorndike1 as a result of experiments with cages and mazes1 formulated two 8provisional laws10 which are as follows3 8,the ,law of ,effect is that3 of several responses made to the same situation1 those which are accompanied or closely followed by satisfaction to the animal will1 other things being equal1 be more firmly connected with the situation1 so that1 when it recurs1 they will be more likely to recur2 those which are accompanied or closely followed by dissatisfaction to the animal will1 other things being equal1 have their connections with that situation weakened1 so that1 when it recurs1 they will be less likely to recur4 ,the greater the satisfaction or discomfort1 the greater the strengthening or weakening of the bond4 8,the ,law of ,exercise is that3 ,any response to a situation will1 other things being equal1 be more strongly connected with the situation in proportion to the number of times it has been connected with that situation and to the average vigour and duration of the connections40 ,we may sum up these two laws1 roughly1 in the two statements3 ,first1 an animal tends to repeat what has brought it pleasure2 second1 an animal tends to repeat what it has often done before4 ,neither of these laws is at all surprising1 but1 as we shall see1 there are difficulties in the theory that they are adequate to account for the process of learning in animals4 ,before going further there is a theoretical point to be cleared up4 ,thorndike1 in his first law1 speaks of satisfaction and discomfort1 which are terms belonging to subjective psychology4 ,we cannot observe whether an animal feels satisfaction or feels discomfort2 we can only observe that it behaves in ways that we have become accustomed to interpret as signs of these feelings4 ,thorndike's law1 as it stands1 does not belong to objective psychology1 and is not capable of being experimentally tested4 ,this1 however1 is not so serious an objection as it looks4 ,instead of speaking of a result that brings satisfaction1 we can merely enumerate the results which1 in fact1 have the character which ,thorndike mentions1 namely1 that the animal tends to behave so as to make them recur4 ,the rat in the maze behaves so as to get the cheese1 and when an act has led him to the cheese once1 he tends to repeat it4 ,we may say that this is what we mean when we say that the cheese 8gives satisfaction01 or that the rat 8desires0 the cheese4 ,that is to say1 we may use ,thorndike's 8,law of ,effect0 to give us an objective definition of desire1 satisfaction1 and discomfort4 ,the law should then say3 there are situations such that animals tend to repeat acts which have led to them2 these are the situations which the animal is said to 8desire0 and in which it is said to 8find satisfaction04 ,this objection to ,thorndike's first law is1 therefore1 not very serious1 and need not further trouble us4 ,dr4 ,watson considers one principle alone sufficient to account for all animal and human learning1 namely1 the principle of 8learned reactions40 ,this principle may be stated as follows3 ,when the body of an animal or human being has been exposed sufficiently often to two roughly simultaneous stimuli1 the earlier of them alone tends to call out the response previously called out by the other4 ,although ,i do not agree with ,dr4 ,watson in thinking this principle alone sufficient1 ,i do agree that it is a principle of very great importance4 ,it is the modern form of the principle of 8association04 ,the 8association of ideas0 has played a great part in philosophy1 particularly in ,british philosophy4 ,but it now appears that this is a consequence of a wider and more primitive principle1 namely1 the association of bodily processes4 ,it is this wider principle that is asserted above4 ,let us see what is the nature of the evidence in its favour4 ,our principle becomes verifiable over a much larger field than the older principle owing to the fact that it is movements1 not 8ideas01 that are to be associated4 ,where animals are concerned1 ideas are hypothetical1 but movements can be observed2 even with men1 many movements are involuntary and unconscious4 ,yet animal movements and unconscious involuntary human movements are just as much subject to the law of association as the most conscious ideas4 ,take1 e4g4 the following example 7,watson1 p4 #cc74 ,the pupil of the eye expands in darkness and contracts in bright light2 this is an involuntary and unconscious action of which we only become aware by observing others4 ,now take some person and repeatedly expose him to bright light at the same moment that you ring an electric bell4 ,after a time the electric bell alone will cause his pupils to contract4 ,as far as can be discovered1 all muscles behave in this way4 ,so do glands where they can be tested4 ,it is said that a brass band can be reduced to silence by sucking a lemon in front of it1 owing to the effect upon the salivary glands of its members2 ,i confess that ,i have never verified this statement4 ,but you will find the exact scientific analogue for dogs in ,watson1 p4 #bf4 ,you arrange a tube in a dog's mouth so that saliva drops out at a measurable rate4 ,when you give the dog food it stimulates the flow of saliva4 ,at the same moment you touch his left thigh4 ,after a certain length of time the touch on the left thigh will produce just as much saliva without the food as with it4 ,the same sort of thing applies to emotions1 which depend upon the ductless glands4 ,children at birth are afraid of loud noises1 but not of animals4 ,watson took a child eleven months old1 who was fond of a certain white rat2 twice at the moment when the child touched the rat1 a sudden noise was made just behind the child's head4 ,this was enough to cause fear of the rat on subsequent occasions1 no doubt owing to the fact that the adrenal gland was now stimulated by the substitute stimulus1 just like the salivary glands in the dog or the trumpet player4 ,the above illustrations show that 8ideas0 are not the essential units in association4 ,it seems that not merely is 8mind0 irrelevant1 but even the brain is less important than was formerly supposed4 ,at any rate1 what is known experimentally is that the glands and muscles 7both striped and unstriped7 of the higher animals exhibit the law of transfer of response1 i4e4 when two stimuli have often been applied together1 one will ultimately call out the response which formerly the other called out4 ,this law is one of the chief bases of habit4 ,it is also obviously essential to our understanding of language3 the sight of a dog calls up the word 8dog01 and the word 8dog0 calls up some of the responses appropriate to a real dog4 ,there is1 however1 another element in learning1 besides mere habit4 ,this is the element dealt with by ,thorndike's 8,law of ,effect40 ,animals tend to repeat acts which have pleasant consequences1 and to avoid such as have unpleasant consequences4 ,but1 as we saw a moment ago1 8pleasant0 and 8unpleasant0 are words which we cannot verify by objective observation4 ,what we can verify by observation is that an animal seeks situations which in fact have had certain results1 and avoids situations which in fact have had certain other results4 ,moreover1 broadly speaking1 the animal seeks results which tend to survival of itself or its offspring1 and avoids results which tend in the opposite direction4 ,this1 however1 is not invariable4 ,moths seek flames and men seek drink1 though neither is biologically useful4 ,it is only approximately1 in situations long common1 that animals are so adjusted to their environment as to act in a way which is advantageous from a biological standpoint4 ,in fact1 biological utility must never be employed as an explanation1 but only noticed as a frequent characteristic1 of the ways in which animals behave4 ,dr4 ,watson is of the opinion that ,thorndike's 8,law of ,effect0 is unnecessary4 ,he first suggests that only two factors are called for in the explanation of habit1 namely1 frequency and recency4 ,frequency is covered by ,thorndike's 8,law of ,exercise01 but recency1 which is almost certainly a genuine factor1 is not covered by ,thorndike's two laws4 ,that is to say1 when a number of random movements have finally resulted in success1 the more recent of these movements are likely to be repeated earlier1 on a second trial1 than the earlier ones4 ,but ,dr4 ,watson finally abandons this method of dealing with habit-formation in favour of the one law of 8conditioned reflexes0 or 8learned reactions04 ,he says 7,behaviorism1 p4 #aff73 8,only a few psychologists have been interested in the problem4 ,most of the psychologists1 it is to be regretted1 have even failed to see that there is a problem4 ,they believe habit formation is implanted by kind fairies4 ,for example1 ,thorndike speaks of pleasure stamping in the successful movement and displeasure stamping out the unsuccessful movements4 ,most of the psychologists talk1 too1 quite volubly about the formation of new pathways in the brain1 as though there were a group of tiny servants of ,vulcan there who run through the nervous system with hammer and chisel digging new trenches and deepening old ones4 ,i am not sure that the problem when phrased in this way is a soluble one4 ,i feel that there must come some simpler way of envisaging the whole process of habit formation or else it may remain insoluble4 ,since the advent of the conditioned reflex hypothesis in psychology with all of the simplifications 7and ,i am often fearful that it may be an oversimplification67 ,i have had my own laryngeal processes i4e4 what others call 8thoughts0 stimulated to work upon this problem from another angle40 ,i agree with ,dr4 ,watson that the explanations of habit-formation which are usually given are very inadequate1 and that few psychologists have realised either the importance or the difficulty of the problem4 ,i agree also that a great many cases are covered by his formula of the conditioned reflex4 ,he relates a case of a child who once touched a hot radiator1 and afterward avoided it for two years4 ,he adds3 8,if we should keep our old habit terminology1 we should have in this example a habit formed by a single trial4 ,there can be then in this case no #8stamping in of the successful movement' and #8no stamping out of the unsuccessful movement4'0 ,on the basis of such examples1 he believes that the whole of habit-formation can be derived from the principle of the conditioned reflex1 which he formulates as follows 7p4 #afh73 ,stimulus ,x will not now call out reaction ,r2 stimulus ,y will call out reaction ,r 7unconditioned reflex72 but when stimulus ,x is presented first and then ,y 7which does call out ,r7 shortly thereafter1 ,x will thereafter call out ,r4 ,in other words1 stimulus ,x becomes ever thereafter substituted for ,y4 ,this law is so simple1 so important1 and so widely true that there is a danger lest its scope should be exaggerated1 just as1 in the eighteenth century1 physicists tried to explain everything by means of gravitation4 ,but when considered as covering all the ground1 it seems to me to suffer from two opposite defects4 ,in the first place1 there are cases where no habit is set up1 although by the law it should be4 ,in the second place1 there are habits which1 so far as we can see at present1 have a different genesis4 ,to take the first point first3 the word 8pepper0 does not make people sneeze1 though according to the law it should4#d ,words which describe succulent foods will make the mouth water2 voluptuous words will have some of the effect that would be produced by the situations they suggest2 but no words will produce sneezes or the reactions appropriate to tickling4 ,in the diagram given by ,dr4 ,watson 7p4 #ajf71 there are four reflexes which appear to be not sources of conditioned reflexes1 namely sneezing1 hiccoughing1 blinking1 and the ,babinski reflex2 of these1 however1 blinking1 it is suggested 7p4 #ii7 may be really itself a conditioned reflex4 ,there may be some quite straightforward explanation of the fact that some reactions can be produced by substitute stimuli while others cannot1 but none is offered4 ,therefore the law of the conditioned reflex1 as formulated1 is too wide1 and it is not clear what is the principle according to which its scope should be restricted4 #d ,dr4 ,watson apparently entertains hopes of teaching babies to sneeze when they see the pepper box1 but he has not yet done so4 ,see ,behaviorism1 p4 #ij4 ,the second objection to ,dr4 ,watson's law of habit1 if valid1 is more important than the first2 but its validity is more open to question4 ,it is contended that the acts by which solutions of problems are obtained are1 in cases of a certain kind1 not random acts leading to success by mere chance1 but acts proceeding from 8insight01 involving a 8mental0 solution of the problem as a preliminary to the physical solution4 ,this is especially the view of those who advocate ,gestaltpsychologie or the psychology of configuration4 ,we may take1 as typical of their attitude on the subject of learning1 ,khler's ,mentality of ,apes4 ,khler went to ,tenerife with certain chimpanzees in the year #aiac2 owing to the war he was compelled to remain with them until #aiag1 so that his opportunities for study were extensive4 ,he complains of the maze and cage problems set by ,american investigators that they are such as cannot be solved by intelligence4 ,sir ,isaac ,newton himself could not have got out of the ,hampton ,court maze by any method except trial and error4 ,khler1 on the other hand1 set his apes problems which could be solved by what he calls 8insight04 ,he would hang up a banana#e out of reach1 and leave boxes in the neighbourhood so that by standing on the boxes the chimpanzees could reach the fruit4 ,sometimes they had to pile three or even four boxes on top of each other before they could achieve success4 ,then he would put the banana outside the bars of the cage1 leaving a stick inside1 and the ape would get the banana by reaching for it with the stick4 ,on one occasion1 one of them1 named ,sultan1 had two bamboo sticks1 each too short to reach the banana2 after vain efforts followed by a period of silent thought1 he fitted the smaller into the hollow of the other1 and so manufactured one stick which was long enough4 ,it seems1 however1 from the account1 that he first fitted the two together more or less accidentally1 and only then realised that he had found a solution4 ,nevertheless1 his behaviour when he had once realised that one stick could be made by joining the two was scarcely ,watsonian3 there was no longer anything tentative1 but a definite triumph1 first in anticipation and then in action4 ,he was so pleased with his new trick that he drew a number of bananas into his cage before eating any of them4 ,he behaved1 in fact1 as capitalists have behaved with machinery4 #e ,called by ,khler 8the objective10 because the word 8banana0 is too humble for a learned work4 ,the pictures disclose the fact that 8the objective0 was a mere banana4 ,khler says3 8,we can1 from our own experience1 distinguish sharply between the kind of conduct which1 from the very beginning1 arises out of a consideration of the characteristics of a situation1 and one that does not4 ,only in the former case do we speak of insight1 and only that behaviour of animals definitely appears to us intelligent which takes account from the beginning of the lie of the land1 and proceeds to deal with it in a smooth continuous course4 ,hence follows this characteristic3 to set up as the criterion of insight1 the appearance of a complete solution with reference to the whole lay-out of the field40 ,genuine solutions of problems1 ,khler says1 do not improve by repetition2 they are perfect on the first occasion1 and1 if anything1 grow worse by repetition1 when the excitement of discovery has worn off4 ,the whole account that ,khler gives of the efforts of his chimpanzees makes a totally different impression from that of the rats in mazes1 and one is forced to conclude that the ,american work is somewhat vitiated by confining itself to one type of problem1 and drawing from that one type conclusions which it believes to be applicable to all problems of animal learning4 ,it seems that there are two ways of learning1 one by experience1 and the other by what ,khler calls 8insight04 ,learning by experience is possible to most vertebrates1 though rarely1 so far as is known1 to invertebrates4 ,learning by 8insight01 on the contrary1 is not known to exist in any animals lower than the anthropoid apes1 though it would be extremely rash to assert that it will not be revealed by further observations on dogs or rats4 ,unfortunately1 some animals--for instance1 elephants--may be extremely intelligent1 but the practical difficulty and expense of experimentation with them is so great that we are not likely to know much about them for some time to come4 ,however1 the real problem is already sufficiently definite in ,khler's book3 it is the analysis of 8insight0 as opposed to the method of the conditioned reflex4 ,let us first be clear as to the nature of the problem1 when described solely in terms of behaviour4 ,a hungry monkey1 if sufficiently near to a banana1 will perform acts such as1 in circumstances to which it has been accustomed1 have previously enabled it to obtain bananas4 ,this fits well with either ,watson or ,thorndike1 so far4 ,but if these familiar acts fail1 the animal will1 if it has been long without food1 is in good health1 and is not too tired1 proceed to other acts which have never hitherto produced bananas4 ,one may suppose1 if one wishes to follow ,watson1 that these new acts are composed of a number of parts1 each of which1 on some former occasion1 has occurred in a series which ended with the obtaining of the banana4 ,or one may suppose--as ,i think ,thorndike does--that the acts of the baffled animal are random acts1 so that the solution emerges by pure chance4 ,but even in the first hypothesis1 the element of chance is considerable4 ,let us suppose that the acts ,a1 ,b1 ,c1 ,d1 ,e1 have each1 on a former occasion1 been part of a series ending with success1 but that now for the first time it is necessary to perform them all1 and in the right order4 ,it is obvious that1 if they are only combined by chance1 the animal will be lucky if it performs them all in the right order before dying of hunger4 ,but ,khler maintains that to anyone watching his chimpanzees it was obvious they did not obtain 8a composition of the solution out of chance parts04 ,he says 7pp4 #aii-bjj73 8,it is certainly not a characteristic of the chimpanzee1 when he is brought into an experimental situation1 to make any chance movements1 out of which1 among other things1 a non-genuine solution could arise4 ,he is very seldom seen to attempt anything which would have to be considered accidental in relation to the situation 7excepting1 of course1 if his interest is turned away from the objective to other things74 ,as long as his efforts are directed to the objective1 all distinguishable stages of his behaviour 7as with human beings in similar situations7 tend to appear as complete attempts at solutions1 none of which appears as the product of accidentally arrayed parts4 ,this is true1 most of all1 of the solution which is finally successful4 ,certainly it often follows upon a period of perplexity or quiet 7often a period of survey71 but in real and convincing cases1 the solution never appears in a disorder of blind impulses4 ,it is one continuous smooth action1 which can be resolved into its parts only by the imagination of the onlooker2 in reality they do not appear independently4 ,but that in so many #8genuine' cases as have been described1 these solutions as wholes should have arisen from mere chance1 is an entirely inadmissible supposition40 ,thus we may take it as an observed fact that1 so far as overt behaviour is concerned1 there are two objections to the type of theory with which we began1 when considered as covering the whole field4 ,the first objection is that in cases of a certain kind1 the solution appears sooner than it should according to the doctrine of chances2 the second is that it appears as a whole1 i4e4 that the animal1 after a period of quiescence1 suddenly goes through the right series of actions smoothly1 and without hesitation4 ,where human beings are concerned1 it is difficult to obtain such good data as in the case of animals4 ,human mothers will not allow their children to be starved1 and then shut up in a room containing a banana which can only be reached by putting a chair on the table and a footstool on the chair1 and then climbing up without breaking any bones4 ,nor will they permit them to be put into the middle of a ,hampton ,court maze1 with their dinner getting cold outside4 ,perhaps in time the ,state will perform these experiments with the children of political prisoners1 but as yet1 perhaps fortunately1 the authorities are not sufficiently interested in science4 ,one can observe1 however1 that human learning seems to be of both sorts1 namely that described by ,watson and that described by ,khler4 ,i am persuaded that speech is learnt by the ,watsonian method1 so long as it is confined to single words3 often the trial and error1 in later stages1 proceeds sotto voce1 but it takes place overtly at first1 and in some children until their speech is quite correct4 ,the speaking of sentences1 however1 is already more difficult to explain without bringing in the apprehension of wholes which is the thing upon which ,gestaltpsychologie lays stress4 ,in the later stages of learning1 the sort of sudden illumination which came to ,khler's chimpanzees is a phenomenon with which every serious student must be familiar4 ,one day1 after a period of groping bewilderment1 the schoolboy knows what algebra is all about4 ,in writing a book1 my own experience--which ,i know is fairly common1 though by no means universal--is that for a time ,i fumble and hesitate1 and then suddenly ,i see the book as a whole1 and have only to write it down as if ,i were copying a completed manuscript4 ,if these phenomena are to be brought within the scope of behaviourist psychology1 it must be by means of 8implicit0 behaviour4 ,watson makes much use of this in the form of talking to oneself1 but in apes it cannot take quite this form4 ,and it is necessary to have some theory to explain the success of 8implicit0 behaviour1 whether we call it 8thought0 or not4 ,perhaps such a theory can be constructed on ,watson's lines1 but it has certainly not yet been constructed4 ,until the behaviourists have satisfactorily explained the kind of discovery which appears in ,khler's observations1 we cannot say that their thesis is proved4 ,this is a matter which will occupy us again at a later stage2 for the present let us preserve an open mind4 ,,chapter ,,iv ,,language ,the subject of language is one which has not been studied with sufficient care in traditional philosophy4 ,it was taken for granted that words exist to express 8thoughts10 and generally also that 8thoughts0 have 8objects0 which are what the words 8mean04 ,it was thought that1 by means of language1 we could deal directly with what it 8means01 and that we need not analyse with any care either of the two supposed properties of words1 namely that of 8expressing0 thoughts and that of 8meaning0 things4 ,often when philosophers intended to be considering the objects meant by words they were in fact considering only the words1 and when they were considering words they made the mistake of supposing1 more or less unconsciously1 that a word is a single entity1 not1 as it really is1 a set of more or less similar events4 ,the failure to consider language explicitly has been a cause of much that was bad in traditional philosophy4 ,i think myself that 8meaning0 can only be understood if we treat language as a bodily habit1 which is learnt just as we learn football or bicycling4 ,the only satisfactory way to treat language1 to my mind1 is to treat it in this way1 as ,dr4 ,watson does4 ,indeed1 ,i should regard the theory of language as one of the strongest points in favour of behaviourism4 ,man has various advantages over the beasts1 for example1 fire1 clothing1 agriculture1 and tools--not the possession of domestic animals1 for ants have them4 ,but more important than any of these is language4 ,it is not known how or when language arose1 nor why chimpanzees do not speak4 ,i doubt if it is even known whether writing or speech is the older form of language4 ,the pictures made in caves by the ,cro-,magnon men may have been intended to convey a meaning1 and may have been a form of writing4 ,it is known that writing developed out of pictures1 for that happened in historical times2 but it is not known to what extent pictures had been used in pre-historic times as a means of giving information or commands4 ,as for spoken language1 it differs from the cries of animals in being not merely an expression of emotion4 ,animals have cries of fear1 cries expressing pleasure in the discovery of food1 and so on1 and by means of these cries they influence each other's actions4 ,but they do not appear to have any means of expressing anything except emotions1 and then only emotions which they are actually feeling4 ,there is no evidence that they possess anything analogous to narrative4 ,we may say1 therefore1 without exaggeration1 that language is a human prerogative1 and probably the chief habit in which we are superior to the 8dumb0 animals4 ,there are three matters to be considered in beginning the study of language4 ,first3 what words are1 regarded as physical occurrences2 secondly1 what are the circumstances that lead us to use a given word2 thirdly1 what are the effects of our hearing or seeing a given word4 ,but as regards the second and third of these questions1 we shall find ourselves led on from words to sentences and thus confronted with fresh problems perhaps demanding rather the methods of ,gestaltpsychologie4 ,ordinary words are of four kinds3 spoken1 heard1 written1 and read4 ,it is of course largely a matter of convention that we do not use words of other kinds4 ,there is the deaf-and-dumb language2 a ,frenchman's shrug of the shoulders is a word2 in fact1 any kind of externally perceptible bodily movement may become a word1 if social usage so ordains4 ,but the convention which has given the supremacy to speaking is one which has a good ground1 since there is no other way of producing a number of perceptibly different bodily movements so quickly or with so little muscular effort4 ,public speaking would be very tedious if statesmen had to use the deaf-and-dumb language1 and very exhausting if all words involved as much muscular effort as a shrug of the shoulders4 ,i shall ignore all forms of language except speaking1 hearing1 writing1 and reading1 since the others are relatively unimportant and raise no special psychological problems4 ,a spoken word consists of a series of movements in the larynx and the mouth1 combined with breath4 ,two closely similar series of such movements may be instances of the same words1 though they may also not be1 since two words with different meanings may sound alike2 but two such series which are not closely similar cannot be instances of the same word4 7,i am confining myself to one language47 ,thus a single spoken word1 say 8dog10 is a certain set of closely similar series of bodily movements1 the set having as many members as there are occasions when the word 8dog0 is pronounced4 ,the degree of similarity required in order that the occurrence should be an instance of the word 8dog0 cannot be specified exactly4 ,some people say 8dawg01 and this must certainly be admitted4 ,a ,german might say 8tok01 and then we should begin to be doubtful4 ,in marginal cases1 we cannot be sure whether a word has been pronounced or not4 ,a spoken word is a form of bodily behaviour without sharp boundaries1 like jumping or hopping or running4 ,is a man running or walking8 ,in a walking-race the umpire may have great difficulty in deciding4 ,similarly there may be cases where it cannot be decided whether a man has said 8dog0 or 8dock04 ,a spoken word is thus at once general and somewhat vague4 ,we usually take for granted the relation between a word spoken and a word heard4 8,can you hear what ,i say80 we ask1 and the person addressed says 8yes04 ,this is of course a delusion1 a part of the naive realism of our unreflective outlook on the world4 ,we never hear what is said2 we hear something having a complicated causal connection with what is said4 ,there is first the purely physical process of sound-waves from the mouth of the speaker to the ear of the hearer1 then a complicated process in the ear and nerves1 and then an event in the brain1 which is related to our hearing of the sound in a manner to be investigated later1 but is at any rate simultaneous with our hearing of the sound4 ,this gives the physical causal connection between the word spoken and the word heard4 ,there is1 however1 also another connection of a more psychological sort4 ,when a man utters a word1 he also hears it himself1 and so that the word spoken and the word heard become intimately associated for anyone who knows how to speak4 ,and a man who knows how to speak can also utter any word he hears in his own language1 so that the association works equally well both ways4 ,it is because of the intimacy of this association that the plain man identifies the word spoken with the word heard1 although in fact the two are separated by a wide gulf4 ,in order that speech may serve its purpose1 it is not necessary1 as it is not possible1 that heard and spoken words should be identical1 but it is necessary that when a man utters different words the heard words should be different1 and when he utters the same word on two occasions the heard word should be approximately the same on the two occasions4 ,the first of these depends upon the sensitiveness of the ear and its distance from the speaker2 we cannot distinguish between two rather similar words if we are too far off from the man who utters them4 ,the second condition depends upon uniformity in the physical conditions1 and is realised in all ordinary circumstances4 ,but if the speaker were surrounded by instruments which were resonant to certain notes but not to certain others1 some tones of voice might carry and others might be lost4 ,in that case1 if he uttered the same word with two different intonations1 the hearer might be quite unable to recognise the sameness4 ,thus the efficacy of speech depends upon a number of physical conditions4 ,these1 however1 we will take for granted1 in order to come as soon as possible to the more psychological parts of our topic4 ,written words differ from spoken words in being material structures4 ,a spoken word is a process in the physical world1 having an essential time-order2 a written word is a series of pieces of matter1 having an essential space-order4 ,as to what we mean by 8matter01 that is a question with which we shall have to deal at length at a later stage4 ,for the present it is enough to observe that the material structures which constitute written words1 unlike the processes that constitute spoken words1 are capable of enduring for a long time--sometimes for thousands of years4 ,moreover1 they are not confined to one neighbourhood1 but can be made to travel about the world4 ,these are the two great advantages of writing over speech4 ,this1 at least1 has been the case until recently4 ,but with the coming of radio writing it has begun to lose its pre-eminence3 one man can now speak to multitudes spread over a whole country4 ,even in the matter of permanence1 speech may become the equal of writing4 ,perhaps1 instead of legal documents1 we shall have gramophone records1 with voice signatures by the parties to the contract4 ,perhaps1 as in ,wells's ,when the ,sleeper ,awakes1 books will no longer be printed but merely arranged for the gramophone4 ,in that case the need for writing may almost cease to exist4 ,however1 let us return from these speculations to the world of the present day4 ,the word read1 as opposed to the written or printed word1 is just as evanescent as the word spoken or heard4 ,whenever a written word1 exposed to light1 is in a suitable spatial relation to a normal eye1 it produces a certain complicated effect upon the eye2 the part of this process which occurs outside the eye is investigated by the science of light1 whereas the part that occurs in the eye belongs to physiological optics4 ,there is then a further process1 first in the optic nerve and afterwards in the brain2 the process in the brain is simultaneous with vision4 ,what further relation it has to vision is a question as to which there has been much philosophical controversy2 we shall return to it at a later stage4 ,the essence of the matter1 as regards the causal efficacy of writing1 is that the act of writing produces quasi-permanent material structures which1 throughout the whole of their duration1 produce closely similar results upon all suitably placed normal eyes2 and as in the case of speaking1 different written words lead to different read words1 and the same word written twice leads to the same read word--again with obvious limitations4 ,so much for the physical side of language1 which is often unduly neglected4 ,i come now to the psychological side1 which is what really concerns us in this chapter4 ,the two questions we have to answer1 apart from the problems raised by sentences as opposed to words1 are3 ,first1 what sort of behaviour is stimulated by hearing a word8 ,and secondly1 what sort of occasion stimulates us to the behaviour that consists in pronouncing a word8 ,i put the questions in this order because children learn to react to the words of others before they learn to use words themselves4 ,it might be objected that1 in the history of the race1 the first spoken word must have preceded the first heard word1 at least by a fraction of a second4 ,but this is not very relevant1 nor is it certainly true4 ,a noise may have meaning to the hearer1 but not to the utterer2 in that case it is a heard word but not a spoken word4 7,i shall explain what ,i mean by 8meaning0 shortly47 ,friday's footprint had 8meaning0 for ,robinson ,crusoe but not for ,friday4 ,however that may be1 we shall do better to avoid the very hypothetical parts of anthropology that would be involved1 and take up the learning of language as it can be observed in the human infant of the present day4 ,and in the human infant as we know him1 definite reactions to the words of others come much earlier than the power of uttering words himself4 ,a child learns to understand words exactly as he learns any other process of bodily association4 ,if you always say 8bottle0 when you give a child his bottle1 he presently reacts to the word 8bottle01 within limits1 as he formerly reacted to the bottle4 ,this is merely an example of the law of association which we considered in the preceding chapter4 ,when the association has been established1 parents say that the child 8understands0 the word 8bottle01 or knows what the word 8means04 ,of course the word does not have all the effects that the actual bottle has4 ,it does not exert gravitation1 it does not nourish1 it cannot bump on to the child's head4 ,the effects which are shared by the word and the thing are those which depend upon the law of association or 8conditional reflexes0 or 8learned reactions04 ,these may be called 8associative0 effects or 8mnemic0 effects--the latter name being derived from ,semon's book ,mneme1#f in which he traces all phenomena analogous to memory to a law which is1 in effect1 not very different from the law of association or 8conditioned reflexes04 #f ,london3 ,george ,allen ,unwin1 ,ltd4 ,it is possible to be a little more precise as to the class of effects concerned4 ,a physical object is a centre from which a variety of causal chains emanate4 ,if the object is visible to ,john ,smith1 one of the causal chains emanating from it consists first of light-waves 7or light-quanta7 which travel from the object to ,john ,smith's eye1 then of events in his eye and optic nerve1 then of events in his brain1 and then 7perhaps7 of a reaction on his part4 ,now mnemic effects belong only to events in living tissue2 therefore only those effects of the bottle which happen either inside ,john ,smith's body1 or as a result of his reaction to the bottle1 can become associated with his hearing the word 8bottle04 ,and even then only certain events can be associated3 nourishment happens in the body1 yet the word 8bottle0 cannot nourish4 ,the law of conditioned reflexes is subject to ascertainable limitations1 but within its limits it supplies what is wanted to explain the understanding of words4 ,the child becomes excited when he sees the bottle2 this is already a conditioned reflex1 due to experience that this sight precedes a meal4 ,one further stage in conditioning makes the child grow excited when he hears the word 8bottle04 ,he is then said to 8understand0 the word4 ,we may say1 then1 that a person understands a word which he hears if1 so far as the law of conditioned reflexes is applicable1 the effects of the word are the same as those of what it is said to 8mean04 ,this of course only applies to words like 8bottle01 which denote some concrete object or some class of concrete objects4 ,to understand a word such as 8reciprocity0 or 8republicanism0 is a more complicated matter1 and cannot be considered until we have dealt with sentences4 ,but before considering sentences we have to examine the circumstances which make us use a word1 as opposed to the consequences of hearing it used4 ,saying a word is more difficult than using it1 except in the case of a few simple sounds which infants make before they know that they are words1 such as 8ma-ma0 and 8da-da40 ,these two are among the many random sounds that all babies make4 ,when a child says 8ma-ma0 in the presence of his mother by chance she thinks he knows what this noise means1 and she shows pleasure in ways that are agreeable to the infant4 ,gradually1 in accordance with ,thorndike's law of effect1 he acquires the habit of making this noise in the presence of his mother1 because in these circumstances the consequences are pleasant4 ,but it is only a very small number of words that are acquired in this way4 ,the great majority of words are acquired by imitation1 combined with the association between thing and word which the parents deliberately establish in the early stages 7after the very first stage74 ,it is obvious that using words oneself involves something over and above the association between the sound of the word and its meaning4 ,dogs understand many words1 and infants understand far more than they can say4 ,the infant has to discover that it is possible and profitable to make noises like those which he hears4 7,this statement must not be taken quite literally1 or it would be too intellectualistic47 ,he would never discover this if he did not make noises at random1 without the intention of talking4 ,he then gradually finds that he can make noises like those which he hears1 and in general the consequences of doing so are pleasant4 ,parents are pleased1 desired objects can be obtained1 and--perhaps most important of all--there is a sense of power in making intended instead of accidental noises4 ,but in this whole process there is nothing essentially different from the learning of mazes by rats4 ,it resembles this form of learning1 rather than that of ,khler apes1 because no amount of intelligence could enable the child to find out the names of things--as in the case of the mazes1 experience is the only possible guide4 ,when a person knows how to speak1 the conditioning proceeds in the opposite direction to that which operates in understanding what others say4 ,the reaction of a person who knows how to speak1 when he notices a cat1 is naturally to utter the word 8cat02 he may not actually do so1 but he will have a reaction leading towards this act1 even if for some reason the overt act does not take place4 ,it is true that he may utter the word 8cat0 because he is 8thinking0 about a cat1 not actually seeing one4 ,this1 however1 as we shall see in a moment1 is merely one further stage in the process of conditioning4 ,the use of single words1 as opposed to sentences1 is wholly explicable1 so far as ,i can see1 by the principles which apply to animals in mazes4 ,certain philosophers who have a prejudice against analysis contend that the sentence comes first and the single word later4 ,in this connection they always allude to the language of the ,patagonians1 which their opponents1 of course1 do not know4 ,we are given to understand that a ,patagonian can understand you if you say 8,i am going to fish in the lake behind the western hill01 but that he cannot understand the word 8fish0 by itself4 7,this instance is imaginary1 but it represents the sort of thing that is asserted47 ,now it may be that ,patagonians are peculiar--indeed they must be1 or they would not choose to live in ,patagonia4 ,but certainly infants in civilized countries do not behave in this way1 with the exception of ,thomas ,carlyle and ,lord ,macaulay4 ,the former never spoke before the age of three1 when1 hearing his younger brother cry1 he said1 8,what ails wee ,jock80 ,lord ,macaulay 8learned in suffering what he taught in song01 for1 having spilt a cup of hot tea over himself at a party1 he began his career as a talker by saying to his hostess1 after a time1 8,thank you1 ,madam1 the agony is abated04 ,these1 however1 are facts about biographers1 not about the beginnings of speech in infancy4 ,in all children that have been carefully observed1 sentences come much later than single words4 ,children1 at first1 are limited as to their power of producing sounds1 and also by the paucity of their learned associations4 ,i am sure the reason why 8ma-ma0 and 8da-da0 have the meaning they have is that they are sounds which infants make spontaneously at an early age1 and are therefore convenient as sounds to which the elders can attach meaning4 ,in the very beginning of speech there is not imitation of grownups1 but the discovery that sounds made spontaneously have agreeable results4 ,imitation comes later1 after the child has discovered that sounds can have this quality of 8meaning04 ,the type of skill involved is throughout exactly similar to that involved in learning to play a game or ride a bicycle4 ,we may sum up this theory of meaning in a simple formula4 ,when through the law of conditioned reflexes1 ,a has come to be a cause of ,c1 we will call ,a an 8associative0 cause of ,c1 and ,c an 8associative0 effect of ,a4 ,we shall say that1 to a given person1 the word ,a1 when he hears it1 8means0 ,c1 if the associative effects of ,a are closely similar to those of ,c2 and we shall say that the word ,a1 when he utters it1 8means0 ,c1 if the utterance of ,a is an associative effect of ,c1 or of something previously associated with ,c4 ,to put the matter more concretely1 the word 8,peter0 means a certain person if the associated effects of hearing the word 8,peter0 are closely similar to those of seeing ,peter1 and the associative causes of uttering the word 8,peter0 are occurrences previously associated with ,peter4 ,of course as our experience increases in complexity this simple schema becomes obscured and overlaid1 but ,i think it remains fundamentally true4 ,there is an interesting and valuable book by ,messrs4 ,c4 ,k4 ,ogden and ,i4 ,a4 ,richards1 called ,the ,meaning of ,meaning4 ,this book1 owing to the fact that it concentrates on the causes of uttering words1 not on the effects of hearing them1 gives only half the above theory1 and that in a somewhat incomplete form4 ,it says that a word and its meaning have the same causes4 ,i should distinguish between active meaning1 that of the man uttering the word1 and passive meaning1 that of the man hearing the word4 ,in active meaning the word is associatively caused by what it means or something associated with this2 in passive meaning1 the associative effects of the word are approximately the same as those of what it means4 ,on behaviourist lines1 there is no important difference between proper names and what are called 8abstract0 or 8generic0 words4 ,a child learns to use the word 8cat01 which is general1 just as he learns to use the word 8,peter01 which is a proper name4 ,but in actual fact 8,peter0 really covers a number of different occurrences1 and is in a sense general4 ,peter may be near or far1 walking or standing or sitting1 laughing or frowning4 ,all these produce different stimuli1 but the stimuli have enough in common to produce the reaction consisting of the word 8,peter04 ,thus there is no essential difference1 from a behaviourist point of view1 between 8,peter0 and 8man04 ,there are more resemblances between the various stimuli to the word 8,peter0 than between those to the word 8man01 but this is only a difference of degree4 ,we have not names for the fleeting particular occurrences which make up the several appearances of ,peter1 because they are not of much practical importance2 their importance1 in fact1 is purely theoretic and philosophical4 ,as such1 we shall have a good deal to say about them at a later stage4 ,for the present1 we notice that there are many occurrences of ,peter1 and many occurrences of the word 8,peter02 each1 to the man who sees ,peter1 is a set of events having certain similarities4 ,more exactly1 the occurrences of ,peter are causally connected1 whereas the occurrences of the word 8,peter0 are connected by similarity4 ,but this is a distinction which need not concern us yet4 ,general words such as 8man0 or 8cat0 or 8triangle0 are said to denote 8universals01 concerning which1 from the time of ,plato to the present day1 philosophers have never ceased to debate4 ,whether there are universals1 and1 if so1 in what sense1 is a metaphysical question1 which need not be raised in connection with the use of language4 ,the only point about universals that needs to be raised at this point is that the correct use of general words is no evidence that a man can think about universals4 ,it has often been supposed that1 because we can use a word like 8man0 correctly1 we must be capable of a corresponding 8abstract0 idea of man1 but this is quite a mistake4 ,some reactions are appropriate to one man1 some to another1 but all have certain elements in common4 ,if the word 8man0 produces in us the reactions which are common but no others1 we may be said to understand the word 8man04 ,in learning geometry1 one acquires the habit of avoiding special interpretations of such a word as 8triangle04 ,we know that1 when we have a proposition about triangles in general1 we must not think specially of a right-angled triangle or any one kind of triangle4 ,this is essentially the process of learning to associate with the word what is associated with all triangles2 when we have learnt this1 we understand the word 8triangle04 ,consequently there is no need to suppose that we ever apprehend universals1 although we use general words correctly4 ,hitherto we have spoken of single words1 and among these we have considered only those that can naturally be employed singly4 ,a child uses single words of a certain kind before constructing sentences2 but some words presuppose sentences4 ,no one would use the word 8paternity0 until after using such sentences as 8,john is the father of ,james02 no one would use the word 8causality0 until after using such sentences as 8the fire makes me warm04 ,sentences introduce new considerations1 and are not quite so easily explained on behaviourist lines4 ,philosophy1 however1 imperatively demands an understanding of sentences1 and we must therefore consider them4 ,as we found earlier1 all infants outside ,patagonia begin with single words1 and only achieve sentences later4 ,but they differ enormously in the speed with which they advance from the one to the other4 ,my own two children adopted entirely different methods4 ,my son first practised single letters1 then single words1 and only achieved correct sentences of more than three or four words at the age of two and three months4 ,my daughter1 on the contrary1 advanced very quickly to sentences1 in which there was hardly ever an error4 ,at the age of eighteen months1 when supposed to be sleeping1 she was overheard saying to herself3 8,last year ,i used to dive off the diving-board1 ,i did40 ,of course 8last year0 was merely a phrase repeated without understanding4 ,and no doubt the first sentences used by children are always repetitions1 unchanged1 of sentences they have heard used by others4 ,such cases raise no new principle not involved in the learning of words4 ,what does raise a new principle is the power of putting together known words into a sentence which has never been heard1 but which expresses correctly what the infant wishes to convey4 ,this involves the power to manipulate form and structure4 ,it does not of course involve the apprehension of form or structure in the abstract1 any more than the use of the word 8man0 involves apprehension of a universal4 ,but it does involve a causal connection between the form of the stimulus and the form of the reaction4 ,an infant very soon learns to be differently affected by the statement 8cats eat mice0 from the way he would be affected by the statement 8mice eat cats02 and not much later he learns to make one of these statements rather than the other4 ,in such a case1 the cause 7in hearing7 or the effect 7in speaking7 is a whole sentence4 ,it may be that one part of the environment is sufficient to cause one word1 while another is sufficient to cause another1 but it is only the two parts in their relation that can cause the whole sentence4 ,thus wherever sentences come in we have a causal relation between two complex facts1 namely the fact asserted and the sentence asserting it2 the facts as wholes enter into the cause-and-effect relation1 which cannot be explained wholly as compounded of relations between their parts4 ,moreover1 as soon as the child has learned to use correctly relational words1 such as 8eat01 he has become capable of being causally affected by a relational feature of the environment1 which involves a new degree of complexity not required for the use of ordinary nouns4 ,thus the correct use of relational words1 i4e4 of sentences1 involves what may be correctly termed 8perception of form01 i4e4 it involves a definite reaction to a stimulus which is a form4 ,suppose1 for example1 that a child has learnt to say that one thing is 8above0 another when this is in fact the case4 ,the stimulus to the use of the word 8above0 is a relational feature of the environment1 and we may say that this feature is 8perceived0 since it produces a definite reaction4 ,it may be said that the relation above is not very like the word 8above04 ,that is true2 but the same is true of ordinary physical objects4 ,a stone1 according to the physicists1 is not at all like what we see when we look at it1 and yet we may be correctly said to 8perceive0 it4 ,this1 however1 is to anticipate4 ,the definite point which has emerged is that1 when a person can use sentences correctly1 that is a proof of sensitiveness to formal or relational stimuli4 ,the structure of a sentence asserting some relational fact1 such as 8this is above that01 or 8,brutus killed ,csar01 differs in an important respect from the structure of the fact which it asserts4 ,above is a relation which holds between the two terms 8this0 and 8that02 but the word 8above0 is not a relation4 ,in the sentence the relation is the temporal order of the words 7or the spatial order1 if they are written71 but the word for the relation is itself as substantial as the other words4 ,in inflected languages1 such as ,latin1 the order of the words is not necessary to show the 8sense0 of the relation2 but in uninflected languages this is the only way of distinguishing between 8,brutus killed ,csar0 and 8,csar killed ,brutus04 ,words are physical phenomena1 having spatial and temporal relations2 we make use of these relations in our verbal symbolisation of other relations1 chiefly to show the 8sense0 of the relation1 i4e4 whether it goes from ,a to ,b or from ,b to ,a4 ,a great deal of the confusion about relations which has prevailed in practically all philosophies comes from the fact1 which we noticed just now1 that relations are indicated1 not by other relations1 but by words which1 in themselves1 are just like other words4 ,consequently1 in thinking about relations1 we constantly hover between the unsubstantiality of the relation itself and the substantiality of the word4 ,take1 say1 the fact that lightning precedes thunder4 ,if we were to express this by a language closely reproducing the structure of the fact1 we should have to say simply3 8lightning1 thunder01 where the fact that the first word precedes the second means that what the first word means precedes what the second word means4 ,but even if we adopted this method for temporal order1 we should still need words for all other relations1 because we could not without intolerable ambiguity symbolise them also by the order of our words4 ,all this will be important to remember when we come to consider the structure of the world1 since nothing but a preliminary study of language will preserve us from being misled by language in our metaphysical speculations4 ,throughout this chapter ,i have said nothing about the narrative and imaginative uses of words2 ,i have dealt with words in connection with an immediate sensible stimulus closely connected with what they mean4 ,the other uses of words are difficult to discuss until we have considered memory and imagination4 ,in the present chapter ,i have confined myself to a behaviouristic explanation of the effects of words heard as stimuli1 and the causes of words spoken when the words apply to something sensibly present4 ,i think we shall find that other uses of words1 such as the narrative and imaginative1 involve only new applications of the law of association4 ,but we cannot develop this theme until we have discussed several further psychological questions4 ,,chapter ,v ,,perception ,,objectively ,,regarded ,it will be remembered that the task upon which we are at present engaged is the definition of 8knowledge0 as a phenomenon discoverable by an outside observer4 ,when we have said what we can from this objective standpoint1 we will ask ourselves whether anything further1 and if so what1 is to be learnt from the subjective standpoint1 in which we take account of facts which can only be discovered when the observer and the observed are the same person4 ,but for the present we will resolutely confine ourselves to those facts about a human being which another human being can observe1 together with such inferences as can be drawn from these facts4 ,the word 8knowledge0 is very ambiguous4 ,we say that ,watson's rats 8know0 how to get out of mazes1 that a child of three 8knows0 how to talk1 that a man 8knows0 the people with whom he is acquainted1 that he 8knows0 what he had for breakfast this morning1 and that he 8knows0 when ,columbus first crossed the ocean4 ,french and ,german are less ambiguous1 since each has two words for different kinds of 8knowing01 which we tend to confuse in our thoughts because we confuse them in our language4 ,i shall not attempt as yet to deal with knowledge in general1 but rather with certain less general concepts which would ordinarily be included under 8knowledge04 ,and first of all ,i will deal with perception--not as it appears to the perceiver1 but as it can be tested by an outside observer4 ,let us try1 first1 to get a rough preliminary view of the sort of thing we are going to mean by 8perception04 ,one may say that a man 8perceives0 anything that he notices through his senses4 ,this is not a question of the sense-organs alone1 though they are a necessary condition4 ,no man can perceive by sight what is not in his field of vision1 but he may look straight at a thing without perceiving it4 ,i have frequently had the experience--supposed to be characteristic of philosophers--of looking everywhere for my spectacles although they were before my eyes when my search began4 ,we cannot therefore tell what a man is perceiving by observing his sense-organs alone1 though they may enable us to know that he is not perceiving something4 ,the observer can only know that a man is perceiving something if the man reacts in some appropriate manner4 ,if ,i say to a man 8please pass the mustard0 and he thereupon passes it1 it is highly probable that he perceived what ,i said1 although it may of course be a mere coincidence that he passed it at that moment4 ,but if ,i say to him 8the telephone number you want is #bdfg0 and he proceeds to call that number1 the odds against his doing so by mere chance are very great--roughly #aj1jjj to #a4 ,and if a man reads aloud out of a book1 and ,i look over his shoulder and perceive the same words1 it becomes quite fantastic to suppose that he does not perceive the words he is uttering4 ,we can thus in many cases achieve practical certainty as to some of the things that other people are perceiving4 ,perception is a species of a wider genus1 namely sensitivity4 ,sensitivity is not confined to living things2 in fact it is best exemplified by scientific instruments4 ,a material object is said to be 8sensitive0 to such and such a stimulus1 if1 when the stimulus is present1 it behaves in a way noticeably different from that in which it behaves in the absence of the stimulus4 ,a photographic plate is sensitive to light1 a barometer is sensitive to pressure1 a thermometer to temperature1 a galvanometer to electric current1 and so on4 ,in all these cases1 we might say1 in a certain metaphorical sense1 that an instrument 8perceives0 the stimulus to which it is sensitive4 ,we do not in fact say so2 we feel that perception involves something more than we find in scientific instruments4 ,what is this something more8 ,the traditional answer would be3 consciousness4 ,but this answer1 right or wrong1 is not what we are seeking at the moment1 because we are considering the percipient as he appears to an outside observer1 to whom his 8consciousness0 is only an inference4 ,is there anything in perception as viewed from without that distinguishes it from the sensitivity of a scientific instrument8 ,there is1 of course1 the fact that human beings are sensitive to a greater variety of stimuli than any instrument4 ,each separate sense-organ can be surpassed by something made artificially sensitive to its particular stimulus4 ,photographic plates can photograph stars that we cannot see2 clinical thermometers register differences of temperature that we cannot feel2 and so on4 ,but there is no way of combining a microscope1 a microphone1 a thermometer1 a galvanometer1 and so on1 into a single organism which will react in an integral manner to the combination of all the different stimuli that affect its different 8sense-organs04 ,this1 however1 is perhaps only a proof that our mechanical skill is not so great as it may in time become4 ,it is certainly not enough to define the difference between a dead instrument and a living body4 ,the chief difference--perhaps the only one from our present point of view--is that living bodies are subject to the law of association or of the 8conditioned reflex04 ,consider1 for instance1 an automatic machine4 ,it has a reflex which makes it sensitive to pennies1 in response to which it gives up chocolate4 ,but it never learns to give up chocolate on merely seeing a penny1 or hearing the word 8penny04 ,if you kept it in your house1 and said 8,abracadabra0 to it every time you inserted a penny1 it would not in the end be moved to action by the mere word 8,abracadabra04 ,its reflexes remain unconditioned1 as do some of ours1 such as sneezing4 ,but with us sneezing is peculiar in this respect--hence its unimportance4 ,most of our reflexes can be conditioned1 and the conditioned reflex can in turn be conditioned afresh1 and so on without limit4 ,this is what makes the reactions of the higher animals1 and especially of man1 so much more interesting and complicated than the reactions of machines4 ,let us see whether this one law will suffice to distinguish perception from other forms of sensitivity4 ,the variability in a human being's responses to a given stimulus has given rise to the traditional distinction between cognition and volition4 ,when one's rich uncle comes for a visit1 smiles are the natural response2 after he has lost his money1 a colder demeanour results from the new conditioning4 ,thus the reaction to the stimulus has come to be divided into two parts1 one purely receptive and sensory1 the other active and motor4 ,perception1 as traditionally conceived1 is1 so to speak1 the end term of the receptive-sensory part of the reaction1 while volition 7in its widest sense7 is the first term of the active-motor part of the reaction4 ,it was possible to suppose that the receptive part of the reaction would be always the same for the same stimulus1 and that the difference due to experience would only arise in the motor part4 ,the last term of the passive part1 as it appears to the person concerned1 was called 8sensation04 ,but in fact the influence of the law of conditioned reflexes goes much deeper than this theory supposed4 ,as we saw1 the contraction of the pupil1 which is normally due to bright light1 can be conditioned so as to result from a loud noise4 ,what we see depends largely upon muscular adjustments of the eyes1 which we make quite unconsciously4 ,but apart from the contraction of the pupil only one of them is a true reflex1 namely turning the eyes towards a bright light4 ,this is a movement which children can perform on the day of their birth2 ,i know this1 not merely from personal observation1 but also1 what is more1 from the text-books4 ,but new-born infants cannot follow a moving light with their eyes1 nor can they focus or accommodate4 ,as a consequence1 the purely receptive part of their reaction to visual objects1 in so far as this reaction is visual1 is different from that of adults or older children1 whose eye muscles adjust themselves so as to see clearly4 ,but here again all sorts of factors enter in4 ,innumerable objects are in our field of vision1 but only some 7at most7 are interesting to us4 ,if some one says 8look1 there's a snake01 we adjust our eyes afresh and obtain a new 8sensation04 ,then1 when the purely visual part is finished1 there are stimulations1 by association1 of other centres in the brain4 ,there are pictures1 in ,khler's book1 of apes watching other apes on the top of insecure piles of boxes1 and the spectators have their arms raised in sympathetic balancing movements4 ,any one who watches gymnastics or skilful dancing is liable to experience sympathetic muscular contractions4 ,any visual object that we might be touching will stimulate incipient touch reactions1 but the sun1 moon1 and stars do not4 ,conversely1 visual reactions may be stimulated through association with other stimuli4 ,when motor-cars were still uncommon1 ,i was walking one day with a friend when a tire punctured in our neighbourhood with a loud report4 ,he thought it was a revolver1 and averred that he had seen the flash4 ,in dreams1 this sort of mechanism operates uncontrolled4 ,some stimulus--say the noise of the maid knocking at the door--becomes interpreted in fantastic ways which are governed by association4 ,i remember once dreaming that ,i was in an inn in the country in ,germany and was wakened by a choir singing outside my window4 ,finally ,i really woke1 and found that a spring shower was making a very musical noise on the roof4 ,at least1 ,i heard a very musical noise1 and now re-interpreted it as a shower on the roof4 ,this hypothesis ,i confirmed by looking out of the window4 ,in waking life we are critical of the interpretative hypotheses that occur to us1 and therefore do not make such wild mistakes as in dreams4 ,but the creative1 as opposed to the critical1 mechanism is the same in waking life as it is in dreams3 there is always far more richness in the experience than the sensory stimulus alone would warrant4 ,all adaptation to environment acquired during the life of the individual might be regarded as learning to dream dreams that succeed rather than dreams that fail4 ,the dreams we have when we are asleep usually end in a surprise3 the dreams we have in waking life are less apt to do so4 ,sometimes they do1 as when pride goes before a fall2 but in that case they are regarded as showing maladjustment1 unless there is some large external cause1 such as an earthquake4 ,one might say that a person properly adapted to his environment is one whose dreams never end in the sort of surprise that would wake him up4 ,in that case1 he will think that his dreams are objective reality4 ,but if modern physics is to be believed1 the dreams we call waking perceptions have only a very little more resemblance to objective reality than the fantastic dreams of sleep4 ,they have some truth1 but only just so much as is required to make them useful4 ,until we begin to reflect1 we unhesitatingly assume that what we see is really 8there0 in the outside world1 except in such cases as reflections in mirrors4 ,physics and the theory of the way in which perceptions are caused show that this naive belief cannot be quite true4 ,perception may1 and ,i think does1 enable us to know something of the outer world1 but it is not the direct revelation that we naturally suppose it to be4 ,we cannot go into this question adequately until we have considered what the philosopher has to learn from physics2 ,i am merely giving1 by anticipation1 the reasons for regarding perception as a form of reaction to the environment1 displayed in some bodily movement1 rather than as a form of knowledge4 ,when we have considered further what constitutes knowledge1 we may find that perception is1 after all1 a form of knowledge1 but only because knowledge is not quite what we naturally suppose it to be4 ,for the present1 let us stick to the view of perception that can be obtained by the external observer1 i4e4 as something displayed in the manner of reacting to the environment4 ,from the point of view of the external observer1 perception is established just like any other causal correlation4 ,we observe that1 whenever a certain object stands in a certain spatial relation to a man's body1 the man's body makes a certain movement or set of movements2 we shall then say that the man 8perceives0 the object4 ,so the new-born baby turns its eyes slowly towards a bright light which is not in the centre of the field of vision2 this entitles us to say that the baby 8perceives0 the light4 ,if he is blind1 his eyes do not move in this way4 ,a bird flying about in a wood does not bump into the branches1 whereas in a room it will bump into the glass of the window4 ,this entitles us to say that the bird perceives the branches but not the glass4 ,do we 8perceive0 the glass or do we merely know that it is there8 ,this question introduces us to the complications produced by association4 ,we know by experience1 from the sense of touch1 that there is usually glass in window-frames2 thus it makes us react to the window-frames as if we could see the glass4 ,but sometimes there is no glass1 and still we shall perhaps behave as if there were4 ,if this can happen1 it shows that we do not perceive the glass1 since our reaction is the same whether there is glass or not4 ,if1 however1 the glass is coloured1 or slightly distorting1 or not perfectly clean1 a person accustomed to glass will be able to distinguish a frame containing glass from one which has none4 ,in that case it is more difficult to decide whether we are to say that he 8perceives0 the glass or not4 ,it is certain that perception is affected by experience4 ,a person who can read perceives print where another would not4 ,a musician perceives differences between notes which to an untrained ear are indistinguishable4 ,people unaccustomed to the telephone cannot understand what they hear in it2 but this is perhaps not really a case in point4 ,the difficulty we are considering arises from the fact that a human body1 unlike a scientific instrument1 is perpetually changing its reaction to a given stimulus1 under the influence of the law of association4 ,moreover1 the human body is always doing something4 ,how1 then1 are we to know whether what it is doing is the result of a given stimulus or not8 ,in most cases1 however1 this difficulty is not very serious1 particularly when we are dealing with people old enough to speak4 ,when you go to the oculist he asks you to read a number of letters growing gradually smaller2 at some point you fail4 ,where you have succeeded1 he knows that you have perceived enough to make out what letter it is4 ,or you take a pair of compasses and press the points into a man's back1 asking him if he feels two pricks or only one4 ,he may say one when the two points are near together2 if he is on his guard against this error he may say two when in fact there is only one4 ,but if the points are sufficiently far apart he will never make a mistake4 ,that is to say1 the bodily movement consisting in pronouncing the word 8two0 will invariably result from a certain stimulus4 7,invariably1 ,i mean1 for a given subject on a given day47 ,this entitles us to say that the man can perceive that there are two points provided they are not too near together4 ,or you say3 8,what can you see on the horizon80 ,one man says1 8,i see a ship04 ,another says1 8,i see a steamer with two funnels04 ,a third says1 8,i see a ,cunarder going from ,southampton to ,new ,york04 ,how much of what these three people say is to count as perception8 ,they may all three be perfectly right in what they say1 and yet we should not concede that a man can 8perceive0 that the ship is going from ,southampton to ,new ,york4 ,this1 we should say1 is inference4 ,but it is by no means easy to draw a line2 some things which are1 in an important sense1 inferential1 must be admitted to be perceptions4 ,the man who says 8,i see a ship0 is using inference4 ,apart from experience1 he only sees a queerly shaped dark dot on a blue background4 ,experience has taught him that that sort of dot 8means0 a ship2 that is to say1 he has a conditioned reflex which causes him to utter1 aloud or to himself1 the word 8ship0 when his eye is stimulated in a certain way4 ,to disentangle what is due to experience1 and what not1 in the perceptions of an adult1 is a hopeless task4 ,practically1 if a word comes without previous verbal intermediaries1 the ordinary man would include what the word means in the perception1 while he would not do so if the man arrives at the word after verbal preliminaries1 overt or internal4 ,but this is itself a question of familiarity4 ,show a child a pentagon1 and he will have to count the sides to know how many there are2 but after a little experience of geometrical figures1 the word 8pentagon0 will arise without any previous words4 ,and in any case such a criterion is theoretically worthless4 ,the whole affair is a matter of degree1 and we cannot draw any sharp line between perception and inference4 ,as soon as this is realised1 our difficulties are seen to be purely verbal and therefore unimportant4 ,it will be observed that we are not attempting at present to say what constitutes perception1 but only what kind of behaviour on the part of a person whom we are observing will justify us in saying that he has perceived this or that feature of his environment4 ,i suggest that we are justified in saying that a man 8perceives0 such a feature if1 throughout some such period as a day1 there is some bodily act which he performs whenever that feature is present1 but not at any other time4 ,this condition is clearly sufficient1 but not necessary--that is to say1 there may be perception even when it is not fulfilled4 ,a man's reaction may change through conditioning1 even in so short a period as a day4 ,again1 there may be a reaction1 but one which is too slight to be observable2 in this case the criterion of perception is theoretically satisfied1 but not practically1 since no one can know that it is4 ,we often have evidence later on that something was perceived1 although at the moment there was no discoverable reaction4 ,i have frequently known children repeat afterwards some remark which1 at the time1 they seemed not to have heard4 ,this sort of case affords another kind of evidence of perception1 namely1 the evidence afforded by a delayed response4 ,some people will sit silent and impassive in a company of talkers1 giving no evidence that they are listening2 yet they may go home and write down the conversation verbatim in their journals4 ,these are the typical writers of memoirs4 ,more remarkable still1 ,i know one man--a man of genius1 it is true--who talks incessantly1 who yet1 after meeting a total stranger1 knows exactly what the stranger would have said if he had been given the chance4 ,how this is managed1 ,i do not know2 but such a man is rightly called 8perceptive04 ,obviously1 in dealing with human beings old enough to talk1 words afford the best evidence of perception4 ,a man's verbal responses to perceptive situations do not change much after the first few years of life4 ,if you see a kingfisher1 and at the same moment your companion says 8there's a kingfisher01 that is pretty conclusive evidence that he saw it4 ,but1 as this case illustrates1 our evidence that some one else has perceived something always depends upon our own perceptions4 ,and our own perceptions are known to us in a different way from that in which the perceptions of others are known to us4 ,this is one of the weak spots in the attempt at a philosophy from the objective standpoint4 ,such a philosophy really assumes knowledge as a going concern1 and takes for granted the world which a man derives from his own perceptions4 ,we cannot tackle all our philosophical problems by the objective method1 but it is worth while to proceed with it as far as it will take us4 ,this whole question of perception will have to be attacked afresh from a different angle1 and we shall then find reason to regard the behaviouristic standpoint as inadequate1 though valid so far as it goes4 ,we have still1 however1 a long road to go before we shall be driven to consider the subjective standpoint2 more particularly1 we have to define 8knowledge0 and 8inference0 behaviouristically1 and then1 making a new start1 to consider what modern physics makes of 8matter04 ,but for the moment there are still some things to be said about perception from the objective standpoint4 ,it will be seen that1 according to our criterion of perception1 an object perceived need not be in contact with the percipient's body4 ,the sun1 moon1 and stars are perceived according to the above criterion4 ,in order1 however1 that an object not in contact with the body should be perceived1 there are physical as well as physiological conditions to be fulfilled4 ,there must be some physical process which takes place at the surface of the body when the object in question is suitably situated1 but not otherwise2 and there must be sense-organs capable of being affected by such a process4 ,there are1 as we know from physics1 many processes which fulfil the necessary physical conditions1 but fail to affect us through the inadequacy of our sense-organs4 ,waves of a certain sort make sound1 but waves of exactly the same sort become inaudible if they are too short4 ,waves of a certain sort make light1 but if they are too long or too short they are invisible4 ,the waves used in wireless are of the same sort as those that make light1 but are too long4 ,there is no reason a priori why we should not be aware of wireless messages through our senses1 without the need of instruments4 ,x-rays are also of the same sort as those that make light1 but in this case they are too short to be seen4 ,they might render the objects from which they come visible1 if we had a different sort of eye4 ,we are not sensitive to magnetism1 unless it is enormously powerful2 but if we had more iron in our bodies1 we might have no need of the mariner's compass4 ,our senses are a haphazard selection of those that the nature of physical processes renders possible2 one may suppose that they have resulted from chance variation and the struggle for existence4 ,it is important to observe that our perceptions are very largely concerned with form or shape or structure4 ,this is the point emphasised by what is called 8,gestaltpsychologie01 or psychology of form4 ,reading is a case in point4 ,whether we read black letters on white paper or white letters on a blackboard is a matter which we hardly notice2 it is the forms of the letters that affect us1 not their colour or their size 7so long as they remain legible74 ,in this matter1 the sense of sight is pre-eminent1 although blind men 7and others to a less degree7 can acquire a good knowledge of form by the sense of touch4 ,another point of importance about our perceptions is that they give us1 within limits1 a knowledge of temporal sequence4 ,if you say to a man 8,brutus killed ,csar01 and then 8,csar killed ,brutus01 the difference between the two statements is likely to be perceived by him if he is listening2 in the one case he will say 8of course01 in the other 8nonsense01 which is evidence of his having different perceptions in the two cases1 according to our definition4 ,further1 if you ask him what the difference is1 he can tell you that it is a difference in the order of the words4 ,thus time-order within a short period of time is clearly perceptible4 ,the objective method1 which we have been applying in this chapter1 is the only possible one in studying the perceptions of animals or of infants before they can talk4 ,many animals too low in the scale of evolution to have eyes are yet sensitive to light1 in the sense that they move towards it or move away from it4 ,such animals1 according to our criterion1 perceive light1 though there is no reason to suppose that they perceive colour or visual form or anything beyond the bare presence of light4 ,we can perceive the bare presence of light when our eyes are shut2 perhaps one may imagine their sensitiveness to be more or less analogous in its limitations4 ,it is not to be supposed1 in any case1 that 8perceiving0 an object involves knowing what it is like4 ,that is quite another matter4 ,we shall see later that certain inferences1 of a highly abstract character1 can be drawn from our perceptions to the objects perceived2 but these inferences are at once difficult and not quite certain4 ,the idea that perception1 in itself1 reveals the character of objects1 is a fond delusion1 and one1 moreover1 which it is very necessary to overcome if our philosophy is to be anything more than a pleasant fairy-tale4 ,,chapter ,,vi ,,memory ,,objectively ,,regarded ,we are concerned in these chapters with what we can know about other men by merely observing their behaviour4 ,in this chapter1 ,i propose to consider everything that would commonly be called 8memory01 in so far as it can be made a matter of external observation4 ,and perhaps it may be as well1 at this point1 to state my own view of the question of 8behaviourism04 ,this philosophy1 of which the chief protagonist is ,dr4 ,john ,b4 ,watson1 holds that everything that can be known about man is discoverable by the method of external observation1 i4e4 that none of our knowledge depends1 essentially and necessarily1 upon data in which the observer and the observed are the same person4 ,i do not fundamentally agree with this view1 but ,i think it contains much more truth than most people suppose1 and ,i regard it as desirable to develop the behaviourist method to the fullest possible extent4 ,i believe that the knowledge to be obtained by this method1 so long as we take physics for granted1 is self-contained1 and need not1 at any point1 appeal to data derived from introspection1 i4e4 from observations which a man can make upon himself but not upon any one else4 ,nevertheless1 ,i hold that there are such observations and that there is knowledge which depends upon introspection4 ,what is more1 ,i hold that data of this kind are required for a critical exposition of physics1 which behaviourism takes for granted4 ,i shall1 therefore1 after setting forth the behaviourist view of man1 proceed to a scrutiny of our knowledge of physics1 returning thence to man1 but now as viewed from within4 ,then1 finally1 ,i shall attempt to draw conclusions as to what we know of the universe in general4 ,the word 8memory0 or 8remembering0 is commonly used in a number of different senses1 which it is important to distinguish4 ,more especially1 there is a broad sense1 in which the word applies to the power of repeating any habitual act previously learnt1 and a narrow sense1 in which it applies only to recollection of past events4 ,it is in the broad sense that people speak of a dog remembering his master or his name1 and that ,sir ,francis ,darwin spoke of memory in plants4 ,samuel ,butler used to attribute the sort of behaviour that would usually be called instinctive to memory of ancestral experience1 and evidently he was using the word 8memory0 in its widest possible sense4 ,bergson1 on the contrary1 dismisses 8habit-memory0 as not true memory at all4 ,true memory1 for him1 is confined to the recollection of a past occurrence1 which1 he maintains1 cannot be a habit1 since the event remembered only occurred once4 ,the behaviourist maintains that this contention is mistaken1 and that all memory consists in the retention of a habit4 ,for him1 therefore1 memory is not something requiring special study1 but is merged into the study of habit4 ,dr4 ,watson says3 8,the behaviourist never uses the term #8memory'4 ,he believes that it has no place in an objective psychology40 ,he proceeds to give instances1 beginning with a white rat in a maze4 ,on the first occasion1 he says1 it took this rat forty minutes to get out of the maze1 but after thirty-five trials he learnt to get out in six seconds1 without taking any wrong turnings4 ,he was then kept away from the maze for six months1 and on being put in it again he got out in two minutes1 with six mistakes4 ,he was just as good as he had been before at the twentieth trial4 ,we have here a measure of the extent to which the habit of the maze had been retained4 ,a similar experiment with a monkey showed even more retentiveness4 ,he was put into a problem box which at first took him twenty minutes to open1 but at the twentieth trial he opened it in two seconds4 ,he was then kept away from it for six months1 and on being put back in it he opened it in four seconds4 ,with human beings1 we know that many of the habits we learn are retained through long periods of disuse--skating1 bicycling1 swimming1 golf1 etc41 are familiar instances4 ,perhaps ,dr4 ,watson goes a trifle too far when he says3 8,if a poor shot or an inexpert golfer tells you that he was good five years ago but that lack of practice has made him poor1 don't believe him2 he never was good60 ,at any rate1 this is not the belief of violinists and pianists1 who consider it essential to practise every day4 ,but even if it be somewhat of an exaggeration1 it is certainly true that we retain bodily habits pretty well4 ,some1 such as swimming1 seem to be more completely retained than others4 ,the power of talking a foreign language1 for example1 is one which is greatly impaired by disuse4 ,the whole matter is quantitative1 and easily tested by experiment4 ,but memory in the sense of recollection of past events1 if it can be explained as a habit1 will have1 one might suppose1 to be a verbal habit4 ,as to this1 ,dr4 ,watson says3 8,what the man on the street ordinarily means by an exhibition of memory is what occurs in some such situation as this3 ,an old friend comes to see him1 after many years' absence4 ,the moment he sees this friend1 he says3 #8,upon my life6 ,addison ,sims of ,seattle6 ,i haven't seen you since the ,world's ,fair in ,chicago4 ,do you remember the gay parties we used to have in the ,wilderness ,hotel8 ,do you remember the ,midway8 ,do you remember 444 etc41' ad infinitum4 ,the psychology of this process is so simple that it seems almost an insult to your intelligence to discuss it1 and yet a good many of the behaviourists' kindly critics have said that behaviourism cannot adequately explain memory4 ,let us see if this is a fact40 ,he goes on to say that during the period1 long ago1 when the man on the street was seeing ,mr4 ,sims1 they formed verbal and manual habits towards one another1 so that 8finally1 just the sight of man1 even after months of absence1 would call out not only the old verbal habits1 but many other types of bodily and visceral responses40 ,he sums up3 8,by #8memory'1 then1 we mean nothing except the fact that when we meet a stimulus again after an absence1 we do the old habitual thing 7say the old words and show the old visceral--emotional--behaviour7 that we learned to do when we were in the presence of that stimulus in the first place40 ,this theory is preferable to ordinary psychological theories in many ways4 ,in the first place1 it is not an attempt to treat memory as some sort of mystical 8faculty01 and does not suppose that we are always remembering everything that we should remember if a suitable stimulus were applied4 ,it is concerned with the causation of specific acts of remembering1 these acts being all externally observable4 ,i do not see any good reason to question it4 ,bergson's contention that the recollection of a unique occurrence cannot be explained by habit is clearly fallacious4 ,there are many instances1 both with animals and with human beings1 of a habit becoming firmly established through one experience4 ,it is1 therefore1 quite possible that a stimulus associated with a previous occurrence should set going a train of bodily events which1 in turn1 produce words describing that occurrence4 ,there is here1 however1 a difficulty4 ,the memory of a past occurrence cannot be a verbal habit1 except when the occurrence has been frequently related4 ,when ,watson's man on the street says 8,do you remember the ,midway01 he is not using words that have become habitual2 very likely he never used these words before4 ,he is using words which a verbal habit associates with an event that is now happening in him1 and the event is called up by a habit associated with ,mr4 ,sims4 ,so at least we must suppose1 if we accept ,watson's view4 ,but this diminishes the plausibility and the verifiability of his view4 ,it is not our actual language that can be regarded as habitual1 but only what our words express4 ,in repeating a poem we have learned by heart1 the language is habitual1 but not so when we recount a past incident in words we never used before4 ,in this case1 it is not the actual words that we repeat1 but only their meaning4 ,the habitual element1 therefore1 if it really accounts for the recollection1 must not be sought in words4 ,this is something of a difficulty in the ,watsonian theory of language4 ,when a rat learns a maze1 it learns certain definite bodily movements2 so do we when we learn by heart4 ,but ,i may say to one person1 8,i met ,mr4 ,jones in the train to-day01 and to another 8,joseph was in the #i4ce this morning40 ,with the exception of the words 8in the01 these two sentences have nothing verbally in common1 yet they may relate the same fact1 and ,i may use either indifferently when ,i recall the fact4 ,thus my recollection is certainly not a definite verbal habit4 ,yet words are the only overt bodily movements by which ,i make known my recollections to other people4 ,if the behaviourist tells me that my recollection is bodily habit1 and begins by telling me that it is a verbal habit1 he can be driven by such instances to the admission that it must be some other kind of habit4 ,if he says this1 he is abandoning the region of observable fact1 and taking refuge in hypothetical bodily movements invoked to save a theory4 ,but these are hardly any better than 8thoughts40 ,this question is more general than the problem of memory4 ,many different forms of words may be used to express the same 8meaning01 and there seems no reason in mere habit to account for the fact that we sometimes use one form of words and sometimes another when we 8think0 of that which all the various forms of words express4 ,the association seems to go1 not direct from stimulus to words1 but from stimulus to 8meaning0 and thence to words expressing the 8meaning04 ,you may1 for instance1 be quite unable to recollect whether you were told 8,jacob is older than ,joseph01 or 8,joseph is younger than ,jacob01 though you may remember quite definitely that you were told the fact which both these forms of words express4 ,again1 if you are learning1 say1 a proof of a mathematical theorem1 you do not learn by heart what the book says1 unless you are a very bad mathematician2 you learn1 as people say1 to 8understand0 the proof1 and then you can reproduce it in symbols quite different from those in the book4 ,it is such facts1 among others1 that make it difficult to explain the mechanism of association1 whether in memory or in 8thought0 in general1 if we assume that words1 or even sentences1 are the terms associated4 ,perhaps1 however1 the theory as to the 8meaning0 of words which we developed in an earlier chapter may help us out of the difficulty4 ,we defined the 8meaning0 of a word by means of its associations2 therefore1 if two words are synonyms1 they have the same associations2 and any stimulus which calls up one may also call up the other4 ,the question which of two synonyms we use will then depend upon some extraneous circumstance4 ,this is all very well so far as single words are concerned2 it would account satisfactorily1 for instance1 for the fact that ,i call a man sometimes by his surname and sometimes by his ,christian name4 ,but it is hardly so adequate when we come to the question of sentences4 ,to revert to the illustration of a moment ago1 in response to the stimulus 8,did anything happen on your journey80 you may say either 8,i met ,mr4 ,jones in the train to-day01 or 8,joseph was in the #i4ce this morning01 or any one of an indefinite number of other sentences expressive of the same occurrence4 ,are we to suppose that1 while you were in the train1 you were rehearsing all these different sentences to yourself1 so that each of them became firmly associated with the words 8journey to-day08 ,clearly such a supposition would be absurd4 ,yet all the separate words of your sentence have many other associations2 it is only the sentence as a whole that is associated with your journey4 ,you have met other people besides ,mr4 ,jones2 you have had other contacts with ,mr4 ,jones besides meeting him this morning2 8train0 and 8to-day0 equally are appropriate to other occurrences that you might relate4 ,thus it has to be the whole sentence that is the associative unit1 and yet the sentence may never have been in your head before4 ,it seems clear that it is possible to state in words something that you remember1 although you never put it into words before4 ,suppose ,i say 8,what did you have for breakfast to-day80 ,probably you will be able to tell me1 though it is very likely that you have not given names to the things you ate until this moment4 ,this whole matter is connected with the distinction between sentences and single words1 which we found important when we were discussing language4 ,but even when we confine ourselves to single words1 there are difficulties in ,dr4 ,watson's view4 ,cases are alleged in which children1 after learning to speak1 can recall incidents which occurred before they could speak1 and describe them in correct words4 ,this would show that the memory had persisted in a non-verbal form throughout the period before they learned to speak1 and had only subsequently found verbal expression4 ,such extreme incidents are rare and might be questioned1 but in a less extreme form it ought not to be difficult to obtain examples of the same sort of thing4 ,suppose1 for example1 that a young child hurt his wrist badly before he knew the word 8wrist01 and that some time afterwards he learnt it2 ,i should not be surprised if he could relate that he had hurt his wrist4 ,such instances1 however1 would not refute the essence of ,watson's theory4 ,he would allow 8visceral0 memory1 for example1 and the association with the word 8wrist0 might be grafted on to this4 ,the real difficulty in ,dr4 ,watson's view1 to my mind1 is the fact that our sentence may vary verbally as much as it likes so long as it retains the same 8meaning01 and that we clearly do not rehearse to ourselves beforehand all the possible sentences having the 8meaning0 in question4 ,it should be realised that behaviourism loses much of its attractiveness if it is compelled to postulate movements that no one can observe and that there is no other reason to assume4 ,dr4 ,broad1 in his book on ,the ,mind and its ,place in ,nature1 distinguishes between 8molar0 and 8molecular0 behaviourism3 the former assumes only such bodily movements as can be observed1 while the latter allows and utilises hypothetical minute movements1 more especially in the brain4 ,now here we must make a distinction4 ,physics believes in a large number of phenomena which are too minute to be observed even with the strongest microscope1 and if physics is at all correct1 there must be minute movements in all parts of a human body1 of a sort which we can never hope to see4 ,we cannot reasonably demand of the behaviourist that he should abstain from an hypothesis which physics asserts for very good reasons4 ,and in the process which leads from stimulus to reaction there are bound to be small occurrences in the brain1 which1 though they cannot be observed1 are essential to the physiological explanation of what occurs4 ,but when the behaviourist assumes small occurrences for which there is no ground in physics1 and which are needed solely in order to safeguard his theory1 he is in a less strong position4 ,dr4 ,watson asserts1 for instance1 that whenever we 8think0 there are small movements in the larynx which are beginnings of the movements we should make as if we spoke words out loud4 ,it may be that this is true2 certainly ,i am not prepared to deny it4 ,but ,i am not prepared to say that it must be true merely because1 if it were not1 behaviourism would be false4 ,we do not know in advance that behaviourism is true2 we have to find out whether it will explain observed facts4 ,whenever it has to postulate something unobserved merely in order to avoid a refutation1 it weakens its case4 ,and if it maintains1 as1 from ,dr4 ,watson's language1 it seems to do1 that we only remember an occurrence by forming a verbal habit in connection with it1 then it is obliged to postulate much implicit use of words of which we have no evidence4 ,to sum up this discussion4 ,while it is quite possible1 by behaviourist methods1 to ascertain whether a person remembers a past occurrence or not1 unless he is deliberately obstructing the observer1 and while much memory can be quite adequately explained as habit1 there do seem to be great difficulties in the view that memory consists entirely of habit1 at least in the case of the recollection of an event4 ,these difficulties seem insuperable if we suppose memory to be essentially a verbal habit4 ,they are not insuperable if we postulate sufficient minute unobservable bodily movements4 ,we have not considered whether they can be overcome by introducing data derived from introspection1 since we wish1 for the present1 to maintain a strictly objective attitude to human behaviour4 ,the introspective discussion of memory will be taken up at a later stage4 ,,chapter ,,vii ,,inference ,,as ,a ,,habit ,in this chapter1 we are concerned with inference as it can be observed when practised by some one else4 ,inference is supposed to be a mark of intelligence and to show the superiority of men to machines4 ,at the same time1 the treatment of inference in traditional logic is so stupid as to throw doubt on this claim1 and syllogistic inference1 which was taken as the type from ,aristotle to ,bacon 7exclusive71 is just the sort of thing that a calculating machine could do better than a professor4 ,in syllogistic inference1 you are supposed to know already that all men are mortal and that ,socrates is a man2 hence you deduce1 what you never suspected before1 that ,socrates is mortal4 ,this form of inference does actually occur1 though very rarely4 ,the only instance ,i have ever heard of was supplied by ,dr4 ,f4 ,c4 ,s4 ,schiller4 ,he once produced a comic number of the philosophical periodical ,mind1 and sent copies to various philosophers1 among others to a certain ,german1 who was much puzzled by the advertisements4 ,but at last he argued3 8,everything in this book is a joke1 therefore the advertisements are jokes04 ,i have never come across any other case of new knowledge obtained by means of a syllogism4 ,it must be admitted that1 for a method which dominated logic for two thousand years1 this contribution to the world's stock of information cannot be considered very weighty4 ,the inferences that we actually make in daily life differ from those of syllogistic logic in two respects1 namely1 that they are important and precarious1 instead of being trivial and safe4 ,the syllogism may be regarded as a monument to academic timidity3 if an inference might be wrong1 it was dangerous to draw it4 ,so the medival monks1 in their thinking as in their lives1 sought safety at the expense of fertility4 ,with the ,renaissance1 a more adventurous spirit came into the world1 but at first in philosophy1 it only took the form of following ,greeks other than ,aristotle1 and more especially ,plato4 ,it is only with ,bacon and ,galileo that the inductive method arrived at due recognition3 with ,bacon as a programme which was largely faulty1 but with ,galileo as something which actually led to brilliant results1 namely1 the foundation of modern mathematical physics4 ,unfortunately1 when the pedants got hold of induction1 they set to work to make it as tame and scholastic as deduction had been4 ,they searched for a way of making it always lead to true results1 and in so doing robbed it of its adventurous character4 ,hume turned upon them with sceptical arguments1 proving quite conclusively that if an induction is worth making it may be wrong4 ,thereupon ,kant deluged the philosophic world with muddle and mystery1 from which it is only now beginning to emerge4 ,kant has the reputation of being the greatest of modern philosophers1 but to my mind he was a mere misfortune4 ,induction1 as it appears in the text-books1 consists1 roughly speaking1 in the inference that1 because ,a and ,b have been found often together and never apart1 therefore they are probably always together1 and either may be taken as a sign of the other4 ,i do not wish1 at this stage1 to examine the logical justification of this form of argumentation2 for the present1 ,i am considering it as a practice1 which we can observe in the habits of men and animals4 ,as a practice1 induction is nothing but our old friend1 the law of conditioned reflexes or of association4 ,a child touches a knob that gives him an electric shock2 after that1 he avoids touching the knob4 ,if he is old enough to speak he may state that the knob hurts when it is touched2 he has made an induction based on a single instance4 ,but the induction will exist as a bodily habit even if he is too young to speak1 and it occurs equally among animals1 provided they are not too low in the scale4 ,the theories of induction in logic are what ,freudians call a 8rationalisation02 that is to say1 they consist of reasons invented afterwards to prove that what we have been doing is sensible4 ,it does not follow that they are bad reasons2 in view of the fact that we and our ancestors have managed to exist since the origin of life1 our behaviour and theirs must have been fairly sensible1 even if we and they were unable to prove that it was4 ,this1 however1 is not the point that concerns us at present4 ,what concerns us at present is the fact that verbal induction is a late development of induction in behaviour1 which is nothing more or less than the principle of 8learned reactions04 ,this principle1 as the reader will remember1 states that1 if a certain event calls out a certain response1 and if another event is experienced just before it1 or at the same moment1 in time that other event will tend to call out the response which1 originally1 only the first event would call out4 ,this applies both to muscles and to glands2 it is because it applies to glands that words are capable of causing emotions4 ,moreover1 we cannot set limits to the length of the chain of associations that may be established4 ,if you hold an infant's limbs1 you call out a rage reaction2 this appears to be an 8unlearned reaction04 ,if you1 and no one else1 repeatedly hold an infant's limbs1 the mere sight of you will call out a rage reaction after a time4 ,when the infant learns to talk your name may have the same effect4 ,if1 later1 he learns that you are an optician1 he may come to hate all opticians2 this may lead him to hate ,spinoza because he made spectacles1 and thence he may come to hate metaphysicians and ,jews4 ,for doing so he will no doubt have the most admirable reasons1 which will seem to him to be his real ones2 he will never suspect the process of conditioning by which he has in fact arrived at his enthusiasm for the ,ku ,klux ,klan4 ,this is an example of conditioning in the emotional sphere2 but it is rather in the muscular sphere that we must seek the origin of the practice of induction4 ,domestic animals which are habitually fed by a certain person will run towards that person as soon as they see him4 ,we say that they expect food1 and in fact their behaviour is very like what it would be if they saw food4 ,but really we have only an example of 8conditioning03 they have often seen first the farmer and then the food1 so that in time they react to the farmer as they originally reacted to the food4 ,infants soon learn to react to the sight of the bottle1 although at first they only react to the touch of it4 ,when they can speak1 the same law makes them say 8dinner0 when they hear the dinner-bell4 ,it is quite unnecessary to suppose that they first think 8that bell means dinner01 and then say 8dinner04 ,the sight of dinner 7by previous 8learned reaction07 causes the word 8dinner03 the bell frequently precedes the sight of dinner2 therefore in time the bell produces the word 8dinner04 ,it is only subsequent reflection1 probably at a much later age1 that makes the child say 8,i knew dinner was ready because ,i heard the bell04 ,long before he can say this1 he is acting as if he knew it4 ,and there is no good reason for denying that he knows it1 when he acts as if he did4 ,if knowledge is to be displayed by behaviour1 there is no reason to confine ourselves to verbal behaviour as the sole kind by which knowledge can manifest itself4 ,the situation1 stated abstractly1 is as follows4 ,originally1 stimulus ,a produced reaction ,c2 now stimulus ,b produces it1 as a result of association4 ,thus ,b has become a 8sign0 of ,a1 in the sense that it causes the behaviour appropriate to ,a4 ,all sorts of things may be signs of other things1 but with human beings words are the supreme example of signs4 ,all signs depend upon some practical induction4 ,whenever we read or hear a statement1 its effect upon us depends upon induction in this sense1 since the words are signs of what they mean1 in the sense that we react to them1 in certain respects1 as we should to what they stand for4 ,if some one says to you 8your house is on fire01 the effect upon you is practically the same as if you saw the conflagration4 ,you may1 of course1 be the victim of a hoax1 and in that case your behaviour will not be such as achieves any purpose you have in view4 ,this risk of error exists always1 since the fact that two things have occurred together in the past cannot prove conclusively that they will occur together in the future4 ,scientific induction is an attempt to regularise the above process1 which we may call 8physiological induction04 ,it is obvious that1 as practised by animals1 infants1 and savages1 physiological induction is a frequent source of error4 ,there is ,dr4 ,watson's infant who induced1 from two examples1 that whenever he saw a certain rat there would be a loud noise4 ,there is ,edmund ,burke1 who induced from one example 7,cromwell7 that revolutions lead to military tyrannies4 ,there are savages who argue1 from one bad season1 that the arrival of a white man causes bad crops4 ,the inhabitants of ,siena1 in #acdh1 thought that the ,black ,death was a punishment for their pride in starting to build too large a cathedral4 ,of such examples there is no end4 ,it is very necessary1 therefore1 if possible1 to find some method by which induction can be practised so as to lead1 in general1 to correct results4 ,but this is a problem of scientific method1 with which we will not yet concern ourselves4 ,what does concern us at present is the fact that all inference1 of the sort that really occurs1 is a development of this one principle of conditioning4 ,in practice1 inference is of two kinds1 one typified by induction1 the other by mathematical reasoning4 ,the former is by far the more important1 since1 as we have seen1 it covers all use of signs and all empirical generalisations as well as the habits of which they are the verbal expression4 ,i know that1 from the traditional standpoint1 it seems absurd to talk of inference in most cases of this sort4 ,for example1 you find it stated in the paper that such and such a horse has won the ,derby4 ,according to my own use of words1 you practise an induction when you arrive thence at the belief that that horse has won4 ,the stimulus consists of certain black marks on white paper--or perhaps on pink paper4 ,this stimulus is only connected with horses and the ,derby by association1 yet your reaction is one appropriate to the ,derby4 ,traditionally1 there was only inference where there was a 8mental process01 which1 after dwelling upon the 8premisses01 was led to assert the 8conclusion0 by means of insight into their logical connection4 ,i am not saying that the process which such words as the above are intended to describe never takes place2 it certainly does4 ,what ,i am saying is that1 genetically and causally1 there is no important difference between the most elaborate induction and the most elementary 8learned reaction04 ,the one is merely a developed form of the other1 not something radically different4 ,and our determination to believe in the results of inductions1 even if1 as logicians1 we see no reason to do so1 is really due to the potency of the principle of association2 it is an example--perhaps the most important example--of what ,dr4 ,santayana calls 8animal faith04 ,the question of mathematical reasoning is more difficult4 ,i think we may lay it down that1 in mathematics1 the conclusion always asserts merely the whole or part of the premisses1 though usually in new language4 ,the difficulty of mathematics consists in seeing that this is so in particular cases4 ,in practice1 the mathematician has a set of rules according to which his symbols can be manipulated1 and he acquires technical skill in working according to the rules in the same sort of way as a billiard-player does4 ,but there is a difference between mathematics and billiards3 the rules of billiards are arbitrary1 whereas in mathematics some at least are in some sense 8true04 ,a man cannot be said to understand mathematics unless he has 8seen0 that these rules are right4 ,now what does this consist of8 ,i think it is only a more complicated example of the process of understanding that 8,napoleon0 and 8,bonaparte0 refer to the same person4 ,to explain this1 however1 we must revert to what was said1 in the chapter on 8,language01 about the understanding of form4 ,human beings possess the power of reacting to form4 ,no doubt some of the higher animals also possess it1 though to nothing like the same extent as men do2 and all animals1 except a few of the most intelligent species1 appear to be nearly devoid of it4 ,among human beings1 it differs greatly from one individual to another1 and increases1 as a rule1 up to adolescence4 ,i should take it as what chiefly characterises 8intellect04 ,but let us see1 first1 in what the power consists4 ,when a child is being taught to read1 he learns to recognise a given letter1 say ,h1 whether it is large or small1 black or white or red4 ,however it may vary in these respects his reaction is the same3 he says 8,h04 ,that is to say1 the essential feature in the stimulus is its form4 ,when my boy1 at the age of just under three1 was about to eat a three-cornered piece of bread and butter1 ,i told him it was a triangle4 7,his slices were generally rectangular47 ,next day1 unprompted1 he pointed to triangular bits in the pavement of the ,albert ,memorial1 and called them 8triangles04 ,thus the form of the bread and butter1 as opposed to its edibility1 its softness1 its colour1 etc41 was what had impressed him4 ,this sort of thing constitutes the most elementary kind of reaction to form4 ,now 8matter0 and 8form0 can be placed1 as in the ,aristotelian philosophy1 in a hierarchy4 ,from a triangle we can advance to a polygon1 thence to a figure1 thence to a manifold of points4 ,then we can go on and turn 8point0 into a formal concept1 meaning 8something that has relations which resemble spatial relations in certain formal respects04 ,each of these is a step away from 8matter0 and further into the region of 8form04 ,at each stage the difficulty increases4 ,the difficulty consists in having a uniform reaction 7other than boredom7 to a stimulus of this kind4 ,when we 8understand0 a mathematical expression1 that means that we can react to it in an appropriate manner1 in fact1 that it has 8meaning0 for us4 ,this is also what we mean by 8understanding0 the word 8cat04 ,but it is easier to understand the word 8cat01 because the resemblances between different cats are of a sort which causes even animals to have a uniform reaction to all cats4 ,when we come to algebra1 and have to operate with x and y1 there is a natural desire to know what x and y really are4 ,that1 at least1 was my feeling3 ,i always thought the teacher knew what they really were1 but would not tell me4 ,to 8understand0 even the simplest formula in algebra1 say 7x y7 x #bxy y1 is to be able to react to two sets of symbols in virtue of the form which they express1 and to perceive that the form is the same in both cases4 ,this is a very elaborate business1 and it is no wonder that boys and girls find algebra a bugbear4 ,but there is no novelty in principle after the first elementary perceptions of form4 ,and perception of form consists merely in reacting alike to two stimuli which are alike in form but very different in other respects4 ,for1 when we can do that1 we can say1 on the appropriate occasion1 8that is a triangle02 and this is enough to satisfy the examiner that we know what a triangle is1 unless he is so old-fashioned as to expect us to reproduce the verbal definition1 which is of course a far easier matter1 in which1 with patience1 we might teach even a parrot to succeed4 ,the meanings of complex mathematical symbols are always fixed by rules in relation to the meaning of simpler symbols2 thus their meanings are analogous to those of sentences1 not to those of single words4 ,what was said earlier about the understanding of sentences applies1 therefore1 to any group of symbols which1 in mathematics1 will be declared to have the same meaning as another group1 or part of that meaning4 ,we may sum up this discussion by saying that mathematical inference consists in attaching the same reactions to two different groups of signs1 whose meanings are fixed by convention in relation to their constituent parts1 whereas induction consists1 first1 in taking something as a sign of something else1 and later1 when we have learned to take ,a as a sign of ,b1 in taking ,a as also a sign of ,c4 ,thus the usual cases of induction and deduction are distinguished by the fact that1 in the former1 the inference consists in taking one sign as a sign of two different things1 while in the latter the inference consists in taking two different signs as signs of the same thing4 ,this statement is a little too antithetical to be taken as an exact expression of the whole truth in the matter4 ,what is true1 however1 is that both kinds of inferences are concerned with the relation of a sign to what it signifies1 and therefore come within the scope of the law of association4 ,,chapter ,,viii ,,knowledge ,,behaviouristically ,,considered ,the word 8knowledge01 like the word 8memory01 is avoided by the behaviourist4 ,nevertheless there is a phenomenon commonly called 8knowledge01 which is tested behaviouristically in examinations4 ,i want to consider this phenomenon in this chapter1 with a view to deciding whether there is anything in it that the behaviourist cannot deal with adequately4 ,it will be remembered that1 in ,chapter ,,ii1 we were led to the view that knowledge is a characteristic of the complete process from stimulus to reaction1 or even1 in the cases of sight and hearing1 from an external object to a reaction1 the external object being connected with the stimulus by a chain of physical causation in the outer world4 ,let us1 for the moment1 leave on one side such cases as sight and hearing1 and confine ourselves1 for the sake of definiteness1 to knowledge derived from touch4 ,we can observe touch producing reactions in quite humble animals1 such as worms and sea anemones4 ,are we to say that they have 8knowledge0 of what they touch8 ,in some sense1 yes4 ,knowledge is a matter of degree4 ,when it is regarded in a purely behaviouristic manner1 we shall have to concede that it exists1 in some degree1 wherever there is a characteristic reaction to a stimulus of a certain kind1 and this reaction does not occur in the absence of the right kind of stimulus4 ,in this sense1 8knowledge0 is indistinguishable from 8sensitivity01 which we considered in connection with perception4 ,we might say that a thermometer 8knows0 the temperature1 and that a compass 8knows0 the direction of the magnetic north4 ,this is the only sense in which1 on grounds of observation1 we can attribute knowledge to animals that are low in the scale4 ,many animals1 for example1 hide themselves when exposed to light1 but as a rule not otherwise4 ,in this1 however1 they do not differ from a radiometer4 ,no doubt the mechanism is different1 but the observed molar motion has similar characteristics4 ,wherever there is a reflex1 an animal may be said1 in a sense1 to 8know0 the stimulus4 ,this is1 no doubt1 not the usual sense of 8knowledge01 but it is the germ out of which knowledge in the usual sense has grown1 and without which no knowledge would be possible4 ,knowledge in any more advanced sense is only possible as a result of learning1 in the sense considered in ,chapter ,,iii4 ,the rat that has learned the maze 8knows0 the way out of it2 the boy who has learned certain verbal reactions 8knows0 the multiplication table4 ,between these two cases there is no important difference4 ,in both cases1 we say that the subject 8knows0 something because he reacts in a manner advantageous to himself1 in which he could not react before he had had certain experiences4 ,i do not think1 however1 that we ought to use such a notion as 8advantageous0 in connection with knowledge4 ,what we can observe1 for instance1 with the rat in the maze1 is violent activity until the food is reached1 followed by eating when it is reached2 also a gradual elimination of acts which do not lead to the food4 ,where this sort of behaviour is observed1 we may say that it is directed towards the food1 and that the animal 8knows0 the way to the food when he gets to it by the shortest possible route4 ,but if this view is right1 we cannot define any knowledge acquired by learning except with reference to circumstances toward which an animal's activity is directed4 ,we should say1 popularly1 that the animal 8desires0 such circumstances4 8,desire01 like 8knowledge01 is capable of a behaviouristic definition1 and it would seem that the two are correlative4 ,let us1 then1 spend a little time on the behaviouristic treatment of 8desire04 ,the best example of desire1 from this point of view1 is hunger4 ,the stimulus to hunger is a certain well-ascertained bodily condition4 ,when in this condition1 an animal moves restlessly2 if he sees or smells food1 he moves in a manner which1 in conditions to which he is accustomed1 would bring him to the food2 if he reaches it1 he eats it1 and if the quantity is sufficient he then becomes quiescent4 ,this kind of behaviour may be summarised by saying that a hungry animal 8desires0 food4 ,it is behaviour which is in various ways different from that of inanimate matter1 because restless movements persist until a certain condition is realised4 ,these movements may or may not be the best adapted to realising the condition in question4 ,every one knows about the pike that was put on one side of a glass partition1 with minnows on the other side4 ,he continually bumped his nose on the glass1 and after six weeks gave up the attempt to catch them4 ,when1 after this1 the partition was removed1 he still refrained from pursuing them4 ,i do not know whether the experiment was tried of leaving a possibility of getting to the minnows by a roundabout route4 ,to have learned to take a roundabout route would perhaps have required a degree of intelligence beyond the capacity of fishes2 this is a matter1 however1 which offers little difficulty to dogs or monkeys4 ,what applies to hunger applies equally to other forms of 8desire04 ,every animal has a certain congenital apparatus of 8desires02 that is to say1 in certain bodily conditions he is stimulated to restless activities which tend towards the performance of some reflex1 and if a given situation is often repeated the animal arrives more and more quickly at the performance of the reflex4 ,this last1 however1 is only true of the higher animals2 in the lower1 the whole process from beginning to end is reflex1 and can therefore only succeed in normal circumstances4 ,the higher animals1 and more especially men1 have a larger proportion of learning and a smaller proportion of reflexes in their behaviour1 and are therefore better able to adapt themselves to new circumstances4 ,the helplessness of infants is a necessary condition for the adaptability of adults2 infants have fewer useful reflexes than the young of animals1 but have far more power of forming useful habits1 which can be adapted to circumstances and are not fatally fixed from birth4 ,this fact is intimately connected with the superiority of the human intelligence above that of the brutes4 ,desire is extremely subject to 8conditioning04 ,if ,a is a primitive desire and ,b has on many occasions been a means to ,a1 ,b comes to be desired in the same sense in which ,a was previously desired4 ,it may even happen1 as in misers1 that the desire for ,b completely displaces the desire for ,a1 so that ,b1 when attained1 is no longer used as a means to ,a4 ,this1 however1 is more or less exceptional4 ,in general1 the desire for ,a persists1 although the desire for ,b has a more or less independent life4 ,the 8conditioning0 of primitive desires in human beings is the source of much that distinguishes our life from that of animals4 ,most animals only seek food when they are hungry2 they may1 then1 die of starvation before they find it4 ,men1 on the contrary1 must have early acquired pleasure in hunting as an art1 and must have set out on hunting expeditions before they were actually hungry4 ,a further stage in the conditioning of hunger came with domestic animals2 a still further stage with agriculture4 ,nowadays1 when a man sets to work to earn his living1 his activity is still connected1 though not very directly1 with hunger and the other primitive desires that can be gratified by means of money4 ,these primitive desires are still1 so to speak1 the power station1 though their energy is widely distributed to all sorts of undertakings that seem1 at first sight1 to have no connection with them4 ,consider 8freedom0 and the political activities it inspires2 this is derivable1 by 8conditioning01 from the emotion of rage which ,dr4 ,watson observed in infants whose limbs are not 8free04 ,again we speak of the 8fall0 of empires and of 8fallen0 women2 this is connected with the fear which infants display when left without support4 ,after this excursion into the realm of desire1 we can now return to 8knowledge01 which1 as we saw1 is a term correlative to 8desire01 and applicable to another feature of the same kind of activity4 ,we may say1 broadly1 that a response to a stimulus of the kind involving desire in the above sense shows 8knowledge0 if it leads by the quickest or easiest route to the state of affairs which1 in the above sense1 is behaviouristically the object of desire4 ,knowledge is thus a matter of degree3 the rat1 during its progressive improvements in the maze1 is gradually acquiring more and more knowledge4 ,its 8intelligence quotient01 so far as that particular task is concerned1 will be the ratio of the time it took on the first trial to the time it takes now to get out of the maze4 ,another point1 if our definition of knowledge is accepted1 is1 that there is no such thing as purely contemplative knowledge3 knowledge exists only in relation to the satisfaction of desire1 or1 as we say1 in the capacity to choose the right means to achieve our ends4 ,but can such a definition as the above really stand8 ,does it represent at all the sort of thing that would commonly be called knowledge8 ,i think it does in the main1 but there is need of some discussion to make this clear4 ,in some cases1 the definition is obviously applicable4 ,these are the cases that are analogous to the rat in the maze1 the consideration of which led us to our definition4 ,do you 8know0 the way from ,trafalgar ,square to ,st4 ,pancras8 ,yes1 if you can walk it without taking any wrong turnings4 ,in practice1 you can give verbal proof of such knowledge1 without actually having to walk the distance2 but that depends upon the correlation of names with streets1 and is part of the process of substituting words for things4 ,there may1 it is true1 come doubtful cases4 ,i was once on a bus in ,whitehall1 and my neighbour asked 8,what street is this80 ,i answered him1 not without surprise at his ignorance4 ,he then said1 8,what building is that80 and ,i replied 8,the ,foreign ,office04 ,to this he retorted1 8but ,i thought the ,foreign ,office was in ,downing ,street04 ,this time1 it was his knowledge that surprised me4 ,should we say that he knew where the ,foreign ,office is8 ,the answer is yes or no according to his purpose4 ,from the point of view of sending a letter to it1 he knew2 from the point of view of walking to it1 he did not know4 ,he had1 in fact1 been a ,british ,consul in ,south ,america1 and was in ,london for the first time4 ,but now let us come to cases less obviously within the scope of our definition4 ,the reader 8knows0 that ,columbus crossed the ocean in #adib4 ,what do we mean by saying that he 8knows0 this8 ,we mean1 no doubt1 primarily that writing down this statement is the way to pass examinations1 which is just as useful to us as getting out of the maze is to the rat4 ,but we do not mean only this4 ,there is historical evidence of the fact1 at least ,i suppose there is4 ,the historical evidence consists of printed books and manuscripts4 ,certain rules have been developed by historians as to the conditions in which statements in books or manuscripts may be accepted as true1 and the evidence in our case is 7,i presume7 in accordance with these rules4 ,historical facts often have importance in the present2 for example1 wills1 or laws not yet repealed4 ,the rules for weighing historical evidence are such as will1 in general bring out self-consistent results4 ,two results are self-consistent when1 in relation to a desire to which both are relevant1 they enjoin the same action1 or actions which can form part of the one movement towards the goal4 ,at ,coton1 near ,cambridge1 there is 7or was in my time7 a signpost with two arms pointing in diametrically opposite directions1 and each arm said 8,to ,cambridge04 ,this was a perfect example of self-contradiction1 since the two arms made statements representing exactly opposite actions4 ,and this case illustrates why self-contradiction is to be avoided4 ,but the avoidance of self-contradiction makes great demands upon us2 ,hegel and ,bradley imagined that we could know the nature of the universe by means of this principle alone4 ,in this they were pretty certainly mistaken1 but nevertheless a great deal of our 8knowledge0 depends upon this principle to a greater or less extent4 ,most of our knowledge is like that in a cookery book1 maxims to be followed when occasion arises1 but not useful at every moment of every day4 ,since knowledge may be useful at any time1 we get gradually1 through conditioning1 a general desire for knowledge4 ,the learned man who is helpless in practical affairs is analogous to the miser1 in that he has become absorbed in a means4 ,it should be observed1 also1 that knowledge is neutral as among different purposes4 ,if you know that arsenic is a poison1 that enables you equally to avoid it if you wish to remain in health1 and to take it if you wish to commit suicide4 ,you cannot judge from a man's conduct in relation to arsenic whether he knows that it is a poison or not1 unless you know his desires4 ,he may be tired of life1 but avoid arsenic because he has been told that it is a good medicine2 in this case1 his avoidance of it is evidence of lack of knowledge4 ,but to return to ,columbus3 surely1 the reader will say1 ,columbus really did cross the ,atlantic in #adib1 and that is why we call this statement 8knowledge04 ,this is the definition of 8truth0 as 8correspondence with fact04 ,i think there is an important element of correctness in this definition1 but it is an element to be elicited at a later stage1 after we have discussed the physical world4 ,and it has the defect--as pragmatists have urged--that there seems no way of getting at 8facts0 and comparing them with our beliefs3 all that we ever reach consists of other beliefs4 ,i do not offer our present behaviouristic and pragmatic definition of 8knowledge0 as the only possible one1 but ,i offer it as the one to which we are led if we wish to regard knowledge as something causally important1 to be exemplified in our reactions to stimuli4 ,this is the appropriate point of view when we are studying man from without1 as we have been doing hitherto4 ,there is1 however1 within the behaviourist philosophy1 one important addition to be made to our definition4 ,we began this chapter with sensitivity1 but we went on to the consideration of learned reactions1 where the learning depended upon association4 ,but there is another sort of learning--at least it is prima facie another sort--which consists of increase of sensitivity4 ,all sensitivity in animals and human beings must count as a sort of knowledge2 that is to say1 if an animal behaves1 in the presence of a stimulus of a certain kind1 as it would not behave in the absence of that stimulus then1 in an important sense1 it has 8knowledge0 as regards the stimulus4 ,now it appears that practice--e4g4 in music--very greatly increases sensitivity4 ,we learn to react differently to stimuli which only differ sightly2 what is more1 we learn to react to differences4 ,a violin-player can react with great precision to an interval of a fifth2 if the interval is very slightly greater or less1 his behaviour in tuning is influenced by the difference from a fifth4 ,and as we have already had occasion to notice1 we become1 through practice1 increasingly sensitive to form4 ,all this increased sensitivity must count as increase of knowledge4 ,but in saying this we are not saying anything inconsistent with our earlier definition of knowledge4 ,sensitivity is essential to choosing the right reaction in many cases4 ,to take the cookery-book again2 when it says 8take a pinch of salt01 a good cook knows how much to take1 which is an instance of sensitivity4 ,accurate scientific observation1 which is of great practical importance1 depends upon sensitivity4 ,and so do many of our practical dealings with other people3 if we cannot 8feel0 their moods1 we shall be always getting at cross purposes4 ,the extent to which sensitivity is improved by practice is astonishing4 ,town-bred people do not know whether the weather is warm or cold until they read the weather reports in the paper4 ,an entomologist perceives vastly more beetles in the course of a country walk than other people do4 ,the subtlety with which connoisseurs can distinguish among wines and cigars is the despair of youths who wish to become men of the world4 ,whether this increase of sensitivity can be accounted for by the law of association1 ,i do not know4 ,in many cases1 probably1 it can1 but ,i think sensitiveness to form1 which is the essential element in the more difficult forms of abstract thought as well as in many other matters1 cannot be regarded as derivative from the law of association1 but is more analogous to the development of a new sense4 ,i should therefore include improvement in sensitivity as an independent element in the advancement of knowledge4 ,but ,i do so with some hesitation4 ,the above discussion does not pretend to cover the whole of the ground that has to be covered in discussing the definition of 8knowledge04 ,there are other points of view1 which are also necessary to a complete consideration of the question4 ,but these must wait until1 after considering the physical world1 we come to the discussion of man as viewed from within4 ,,part ,,ii ,,the ,,physical ,,world ,,chapter ,,ix ,,the ,,structure ,,of ,,the ,,atom ,in all that we have said hitherto on the subject of man from without1 we have taken a common-sense view of the material world4 ,we have not asked ourselves3 what is matter8 ,is there such a thing1 or is the outside world composed of stuff of a different kind8 ,and what light does a correct theory of the physical world throw upon the process of perception8 ,these are questions which we must attempt to answer in the following chapters4 ,and in doing so the science upon which we must depend is physics4 ,modern physics1 however1 is very abstract1 and by no means easy to explain in simple language4 ,i shall do my best1 but the reader must not blame me too severely if1 here and there1 he finds some slight difficulty or obscurity4 ,the physical world1 both through the theory of relativity and through the most recent doctrines as to the structure of the atom1 has become very different from the world of everyday life1 and also from that of scientific materialism of the eighteenth-century variety4 ,no philosophy can ignore the revolutionary changes in our physical ideas that the men of science have found necessary2 indeed it may be said that all traditional philosophies have to be discarded1 and we have to start afresh with as little respect as possible for the systems of the past4 ,our age has penetrated more deeply into the nature of things than any earlier age1 and it would be a false modesty to over-estimate what can still be learned from the metaphysicians of the seventeenth1 eighteenth and nineteenth centuries4 ,what physics has to say about matter1 and the physical world generally1 from the standpoint of the philosopher1 comes under two main heads3 first1 the structure of the atom2 secondly1 the theory of relativity4 ,the former was1 until recently1 the less revolutionary philosophically1 though the more revolutionary in physics4 ,until #aibe1 theories of the structure of the atom were based upon the old conception of matter as indestructible substance1 although this was already regarded as no more than a convenience4 ,now1 owing chiefly to two ,german physicists1 ,heisenberg and ,schrdinger1 the last vestiges of the old solid atom have melted away1 and matter has become as ghostly as anything in a spiritualist seance4 ,but before tackling these newer views1 it is necessary to understand the much simpler theory which they have displaced4 ,this theory does not1 except here and there1 take account of the new doctrines on fundamentals that have been introduced by ,einstein1 and it is much easier to understand than relativity4 ,it explains so much of the facts that1 whatever may happen1 it must remain a stepping-stone to a complete theory of the structure of the atom2 indeed1 the newer theories have grown directly out of it1 and could hardly have arisen in any other way4 ,we must therefore spend a little time in giving a bare outline1 which is the less to be regretted as the theory is in itself fascinating4 ,the theory that matter consists of 8atoms01 i4e4 of little bits that cannot be divided1 is due to the ,greeks1 but with them it was only a speculation4 ,the evidence for what is called the atomic theory was derived from chemistry1 and the theory itself1 in its nineteenth-century form1 was mainly due to ,dalton4 ,it was found that there were a number of 8elements01 and that other substances were compounds of these elements4 ,compound substances were found to be composed of 8molecules01 each molecule being composed of 8atoms0 of one substance combined with 8atoms0 of another or of the same4 ,a molecule of water consists of two atoms of hydrogen and one atom of oxygen2 they can be separated by electrolysis4 ,it was supposed1 until radio-activity was discovered1 that atoms were indestructible and unchangeable4 ,substances which were not compounds were called 8elements04 ,the ,russian chemist ,mendeleev discovered that the elements can be arranged in a series by means of progressive changes in their properties2 in his time1 there were gaps in this series1 but most of them have since been filled by the discovery of new elements4 ,if all the gaps were filled1 there would be #ib elements2 actually the number known is #hg1 or1 including three about which there is still some doubt1 #ij4 ,the place of an element in this series is called its 8atomic number04 ,hydrogen is the first1 and has the atomic number #a2 helium is the second1 and has the atomic number #b2 uranium is the last1 and has the atomic number #ib4 ,perhaps in the stars there are elements with higher atomic numbers1 but so far none has been actually observed4 ,the discovery of radio-activity necessitated new views as to 8atoms04 ,it was found that an atom of one radio-active element can break up into an atom of another element and an atom of helium1 and that there is also another way in which it can change4 ,it was found also that there can be different elements having the same place in the series2 these are called 8isotopes04 ,for example1 when radium disintegrates it gives rise1 in the end1 to a kind of lead1 but this is somewhat different from the lead found in lead-mines4 ,a great many 8elements0 have been shown by ,dr4 ,f4 ,w4 ,aston to be really mixtures of isotopes1 which can be sorted out by ingenious methods4 ,all this1 but more especially the transmutation of elements in radio-activity1 led to the conclusion that what had been called 8atoms0 were really complex structures1 which could change into atoms of a different sort by losing a part4 ,after various attempts to imagine the structure of an atom1 physicists were led to accept the view of ,sir ,ernest ,rutherford1 which was further developed by ,niels ,bohr4 ,in this theory1 which1 in spite of recent developments1 remains substantially correct1 all matter is composed of two sorts of units1 electrons and protons4 ,all electrons are exactly alike1 and all protons are exactly alike4 ,all protons carry a certain amount of positive electricity1 and all electrons carry an equal amount of negative electricity4 ,but the mass of a proton is about #ahce times that of an electron3 it takes #ahce electrons to weigh as much as one proton4 ,protons repel each other1 and electrons repel each other1 but an electron and a proton attract each other4 ,every atom is a structure consisting of electrons and protons4 ,the hydrogen atom1 which is the simplest1 consists of one proton with one electron going round it as a planet goes round the sun4 ,the electron may be lost1 and the proton left alone2 the atom is then positively electrified4 ,but when it has its electron1 it is1 as a whole1 electrically neutral1 since the positive electricity of the proton is exactly balanced by the negative electricity of the electron4 ,the second element1 helium1 has already a much more complicated structure4 ,it has a nucleus1 consisting of four protons1 and two electrons very close together1 and in its normal state it has two planetary electrons going round the nucleus4 ,but it may lose either or both of these1 and it is then positively electrified4 ,all the latter elements consist1 like helium1 of a nucleus composed of protons and electrons1 and a number of planetary electrons going round the nucleus4 ,there are more protons than electrons in the nucleus1 but the excess is balanced by the planetary electrons when the atom is unelectrified4 ,the number of protons in the nucleus gives the 8atomic weight0 of the element3 the excess of protons over electrons in the nucleus gives the 8atomic number01 which is also the number of planetary electrons when the atom is unelectrified4 ,uranium1 the last element1 has #bch protons and #adf electrons in the nucleus1 and when unelectrified it has #ib planetary electrons4 ,the arrangement of the planetary electrons in atoms other than hydrogen is not accurately known1 but it is clear that1 in some sense1 they form different rings1 those in the outer rings being more easily lost than those nearer the nucleus4 ,i come now to what ,bohr added to the theory of atoms as developed by ,rutherford4 ,this was a most curious discovery1 introducing1 in a new field1 a certain type of discontinuity which was already known to be exhibited by some other natural processes4 ,no adage had seemed more respectable in philosophy than 8natura non facit saltum01 ,nature makes no jumps4 ,but if there is one thing more than another that the experience of a long life has taught me1 it is that ,latin tags always express falsehoods2 and so it has proved in this case4 ,apparently ,nature does make jumps1 not only now and then1 but whenever a body emits light1 as well as on certain other occasions4 ,the ,german physicist ,planck was the first to demonstrate the necessity of jumps4 ,he was considering how bodies radiate heat when they are warmer than their surroundings4 ,heat1 as has long been known1 consists of vibrations1 which are distinguished by their 8frequency01 i4e4 by the number of vibrations per second4 ,planck showed that1 for vibrations having a given frequency1 not all amounts of energy are possible1 but only those having to the frequency a ratio which is a certain quantity h multiplied by #a or #b or #c or some other whole number1 in practice always a small whole number4 ,the quantity h is known as 8,planck's constant02 it has turned out to be involved practically everywhere where measurement is delicate enough to know whether it is involved or not4 ,it is such a small quantity that1 except where measurement can reach a very high degree of accuracy1 the departure from continuity is not appreciable4#g #g ,the dimensions of h are those of 8action01 i4e4 energy multiplied by time1 or moment of momentum1 or mass multiplied by length multiplied by velocity4 ,its magnitude is about #f4ee #aj4bg erg secs4 ,bohr's great discovery was that this same quantity h is involved in the orbits of the planetary electrons in atoms1 and that it limits the possible orbits in ways for which nothing in ,newtonian dynamics had prepared us1 and for which so far1 there is nothing in relativity-dynamics to account4 ,according to ,newtonian principles1 an electron ought to be able to go round the nucleus in any circle with the nucleus in the centre1 or in any ellipse with the nucleus in a focus2 among possible orbits1 it would select one or another according to its direction and velocity4 ,but in fact only certain out of all these orbits occur4 ,those that occur are among those that are possible on ,newtonian principles1 but are only an infinitesimal selection from among these4 ,it will simplify the explanation if we confine ourselves1 as ,bohr did at first1 to circular orbits2 moreover we will consider only the hydrogen atom1 which has one planetary electron and a nucleus consisting of one proton4 ,to define the circular orbits that are found to be possible1 we proceed as follows3 multiply the mass of the electron by the circumference of its orbit1 and this again by the velocity of the electron2 the result will always be h or #b;h1 or #c;h1 or some other small exact multiple of h1 where h1 as before1 is 8,planck's constant04 ,there is thus a smallest possible orbit1 in which the above product is h2 the radius of the next orbit1 in which the above produce is #b;h1 will have a length four times this minimum2 the next1 nine times2 the next1 sixteen times2 and so on through the 8square numbers0 7i4e4 those got by multiplying a number by itself74 ,apparently no other circular orbits than these are possible in the hydrogen atom4 ,elliptic orbits are possible1 and these again introduce exact multiples of h3 but we need not1 for our purposes1 concern ourselves with them4 ,when a hydrogen atom is left to itself1 if the electron is in the minimum orbit it will continue to rotate in that orbit so long as nothing from outside disturbs it2 but if the electron is in any of the larger possible orbits1 it may sooner or later jump suddenly to a smaller orbit1 either the minimum or one of the intermediate possible orbits4 ,so long as the electron does not change its orbit1 the atom does not radiate energy1 but when the electron jumps to a smaller orbit1 the atom loses energy1 which is radiated out in the form of a light-wave4 ,this light-wave is always such that its energy divided by its frequency is exactly h4 ,the atom may absorb energy from without1 and it does so by the electron jumping to a larger orbit4 ,it may then afterwards1 when the external source of energy is removed1 jump back to the smaller orbit2 this is the cause of fluorescence1 since1 in doing so1 the atom gives out energy in the form of light4 ,the same principles1 with greater mathematical complications1 apply to the other elements4 ,there is1 however1 with some of the latest elements1 a phenomenon which cannot have any analogue in hydrogen1 and that is radio-activity4 ,when an atom is radio-active1 it emits rays of three kinds1 called respectively -rays1 -rays1 and -rays4 ,of these1 the -rays are analogous to light1 but of much higher frequencies1 or shorter wave-lengths2 we need not further concern ourselves with them4 ,the -rays and -rays1 on the contrary1 are important as our chief source of knowledge concerning the nuclei of atoms4 ,it is found that the -rays consist of helium nuclei1 while the -rays consist of electrons4 ,both come out of the nucleus1 since the atom after radio-activity disruption is a different element from what it was before4 ,but no one knows just why the nucleus disintegrates when it does1 nor why1 in a piece of radium1 for example1 some atoms break down while others do not4 ,the three principal sources of our knowledge concerning atoms have been the light they emit1 ,x-rays and radio-activity4 ,as everyone knows1 when the light emitted by a glowing gas is passed through a prism1 it is found to consist of well-defined lines of different colours1 which are characteristic for each element1 and constitute what is called its 8spectrum04 ,the spectrum extends beyond the range of visible light1 both into the infra-red and into the ultra-violet4 ,in the latter direction1 it extends right into the region of ,x-rays1 which are only ultra-ultra-violet light4 ,by means of crystals1 it has been found possible to study ,x-ray spectra as exactly as those of ordinary light4 ,the great merit of ,bohr's theory was that it explained why elements have the spectra they do have1 which had1 before1 been a complete mystery4 ,in the cases of hydrogen and positively electrified helium1 the explanation1 particularly as extended by the ,german physicist ,sommerfeld1 gave the most minute numerical agreement between theory and observation2 in other cases1 mathematical difficulties made this completeness impossible1 but there was every reason to think that the same principles were adequate4 ,this was the main reason for accepting ,bohr's theory2 and certainly it was a very strong one4 ,it was found that visible light enabled us to study the outer rings of planetary electrons1 ,x-rays enabled us to study the inner rings1 and radio-activity enabled us to study the nucleus4 ,for the latter purpose1 there are also other methods1 more particularly ,rutherford's 8bombardment01 which aims at breaking up nuclei by firing projectiles at them1 and sometimes succeeds in making a hit in spite of the smallness of the target4 ,the theory of atomic structure that has just been outlined1 like everything in theoretical physics1 is capable of expression in mathematical formul2 but like many things in theoretical physics1 it is also capable of expression in the form of an imaginative picture4 ,but here1 as always1 it is necessary to distinguish sharply between the mathematical symbols and the pictorial words4 ,the symbols are pretty sure to be right1 or nearly so2 the imaginative picture1 on the other hand1 should not be taken too seriously4 ,when we consider the nature of the evidence upon which the above theory of the atom is based1 we can see that the attempt to make a picture of what goes on has led us to be far more concrete than we have any right to be4 ,if we want to assert only what we have good reason to believe1 we shall have to abandon the attempt to be concrete about what goes on in the atom1 and say merely something like this3 ,an atom with its electrons is a system characterised by certain integers1 all small1 and all capable of changing independently4 ,these integers are the multiples of h involved4 ,when any of them changes to a smaller integer1 energy of a definite amount is emitted1 and its frequency will be obtained by dividing the energy of h4 ,when any of the integers concerned changes to a larger integer1 energy is absorbed1 and again the amount absorbed is definite4 ,but we cannot know what goes on when the atom is neither absorbing nor radiating energy1 since then it has no effects in surrounding regions2 consequently all evidence as to atoms is as to their changes1 not as to their steady states4 ,the point is not that the facts do not fit with the hypothesis of the atom as a planetary system4 ,there are1 it is true1 certain difficulties which afford empirical grounds for the newer theory which has superseded ,bohr's1 and which we shall shortly consider4 ,but even if no such grounds existed1 it would be obvious that ,bohr's theory states more than we have a right to infer from what we can observe4 ,of theories that state so much1 there must be an infinite number that are compatible with what is known1 and it is only what all of these have in common that we are really entitled to assert4 ,suppose your knowledge of ,great ,britain were entirely confined to observing the people and goods that enter and leave the ports2 you could1 in that case1 invent many theories as to the interior of ,great ,britain1 all of which would agree with all known facts4 ,this is an exact analogy4 ,if you delimit in the physical universe any region1 large or small1 not containing a scientific observer1 all scientific observers will have exactly the same experiences whatever happens inside this region1 provided it does not affect the flow of energy across the boundary of the region4 ,and so1 if the region contains one atom1 any two theories which give the same results as to the energy that the atom radiates or absorbs are empirically indistinguishable1 and there can be no reason except simplicity for preferring one of them to the other4 ,on this ground1 even if on no other1 prudence compels us to seek a more abstract theory of the atom than that which we owe to ,rutherford and ,bohr4 ,the newer theory has been put forward mainly by two physicists already mentioned1 ,heisenberg and ,schrdinger1 in forms which look different1 but are in fact mathematically equivalent4 ,it is as yet an impossible task to describe this theory in simple language1 but something can be said to show its philosophical bearing4 ,broadly speaking1 it describes the atom by means of the radiations that come out of it4 ,in ,bohr's theory1 the planetary electrons are supposed to describe orbits over and over again while the atom is not radiating2 in the newer theory1 we say nothing at all as to what happens at these times4 ,the aim is to confine the theory to what is empirically verifiable1 namely radiations2 as to what there is where the radiations come from1 we cannot tell1 and it is scientifically unnecessary to speculate4 ,the theory requires modifications in our conception of space1 of a sort not yet quite clear4 ,it also has the consequence that we cannot identify an electron at one time with an electron at another1 if in the interval1 the atom has radiated energy4 ,the electron ceases altogether to have the properties of a 8thing0 as conceived by common sense2 it is merely a region from which energy may radiate4 ,on the subject of discontinuity1 there is disagreement between ,schrdinger and other physicists4 ,most of them maintain that quantum changes--i4e4 the changes that occur in an atom when it radiates or absorbs energy--must be discontinuous4 ,schrdinger thinks otherwise4 ,this is a matter in debate among experts1 as to which it would be rash to venture an opinion4 ,probably it will be decided one way or other before very long4 ,the main point for the philosopher in the modern theory is the disappearance of matter as a 8thing04 ,it has been replaced by emanations from a locality--the sort of influences that characterise haunted rooms in ghost stories4 ,as we shall see in the next chapter1 the theory of relativity leads to a similar destruction of the solidity of matter1 by a different line of argument4 ,all sorts of events happen in the physical world1 but tables and chairs1 the sun and moon1 and even our daily bread1 have become pale abstractions1 mere laws exhibited in the successions of events which radiate from certain regions4 ,,chapter ,x ,,relativity ,we have seen that the world of the atom is a world of revolution rather than evolution3 the electron which has been moving in one orbit hops quite suddenly into another1 so that the motion is what is called 8discontinuous01 that is to say1 the electron is first in one place and then in another1 without having passed over any intermediate places4 ,this sounds like magic1 and there may be some way of avoiding such a disconcerting hypothesis4 ,at any rate1 nothing of the sort seems to happen in the regions where there are no electrons and protons4 ,in these regions1 so far as we can discover1 there is continuity1 that is to say1 everything goes by gradual transitions1 not by jumps4 ,the regions in which there are no electrons and protons may be called 8ther0 or 8empty space0 as you prefer3 the difference is only verbal4 ,the theory of relativity is especially concerned with what goes on in these regions1 as opposed to what goes on where there are electrons and protons4 ,apart from the theory of relativity1 what we know about these regions is that waves travel across them1 and that these waves1 when they are waves of light or electromagnetism 7which are identical71 behave in a certain fashion set forth by ,maxwell in certain formul called 8,maxwell's equations04 ,when ,i say we 8know0 this1 ,i am saying more than is strictly correct1 because all we know is what happens when the waves reach our bodies4 ,it is as if we could not see the sea1 but could only see the people disembarking at ,dover1 and inferred the waves from the fact that the people looked green4 ,it is obvious1 in any case1 that we can only know so much about the waves as is involved in their having such-and-such causes at one end and such-and-such effects at the other4 ,what can be inferred in this way will be1 at best1 something wholly expressible in terms of mathematical structure4 ,we must not think of the waves as being necessarily 8in0 the ther or 8in0 anything else2 they are to be thought of merely as progressive periodic processes1 whose laws are more or less known1 but whose intrinsic character is not known and never can be4 ,the theory of relativity has arisen from the study of what goes on in the regions where there are no electrons and protons4 ,while the study of the atom has led us to discontinuities1 relativity has produced a completely continuous theory of the intervening medium--far more continuous than any theory formerly imagined4 ,at the moment1 these two points of view stand more or less opposed to each other1 but no doubt before long they will be reconciled4 ,there is not1 even now1 any logical contradiction between them2 there is only a fairly complete lack of connection4 ,for philosophy1 far the most important thing about the theory of relativity is the abolition of the one cosmic time and the one persistent space1 and the substitution of space-time in place of both4 ,this is a change of quite enormous importance1 because it alters fundamentally our notion of the structure of the physical world1 and has1 ,i think1 repercussions in psychology4 ,it would be useless1 in our day1 to talk about philosophy without explaining this matter4 ,therefore ,i shall make the attempt1 in spite of some difficulty4 ,common-sense and pre-relativity physicists believed that1 if two events happen in different places1 there must always be a definite answer1 in theory1 to the question whether they were simultaneous4 ,this is found to be a mistake4 ,let us suppose two persons ,a and ,b a long way apart1 each provided with a mirror and means of sending out light-signals4 ,the events that happen to ,a still have a perfectly definite time-order1 and so have those that happen to ,b2 the difficulty comes in connecting ,a's time with ,b's4 ,suppose ,a sends a flash to ,b1 ,b's mirror reflects it1 and it returns to ,a after a certain time4 ,if ,a is on the earth and ,b on the sun1 the time will be about sixteen minutes4 ,we shall naturally say that the time when ,b received the light-signal is half way between the times when ,a sent it out and received it back4 ,but this definition turns out to be not unambiguous2 it will depend upon how ,a and ,b are moving relatively to each other4 ,the more this difficulty is examined1 the more insuperable it is seen to be4 ,anything that happens to ,a after he sends out the flash and before he gets it back is neither definitely before nor definitely after nor definitely simultaneous with the arrival of the flash at ,b4 ,to this extent1 there is no unambiguous way of correlating times in different places4 ,the notion of a 8place0 is also quite vague4 ,is ,london a 8place08 ,but the earth is rotating4 ,is the earth a 8place08 ,but it is going round the sun4 ,is the sun a 8place08 ,but it is moving relatively to the stars4 ,at best you could talk of a place at a given time2 but then it is ambiguous what is a given time1 unless you confine yourself to one place4 ,so the notion of 8place0 evaporates4 ,we naturally think of the universe as being in one state at one time and in another at another4 ,this is a mistake4 ,there is no cosmic time1 and so we cannot speak of the state of the universe at a given time4 ,and similarly we cannot speak unambiguously of the distance between two bodies at a given time4 ,if we take the time appropriate to one of the two bodies1 we shall get one estimate2 if the time of the other1 another4 ,this makes the ,newtonian law of gravitation ambiguous1 and shows that it needs restatement1 independently of empirical evidence4 ,geometry also goes wrong4 ,a straight line1 for example1 is supposed to be a certain track in space whose parts all exist simultaneously4 ,we shall now find that what is a straight line for one observer is not a straight line for another4 ,therefore geometry ceases to be separable from physics4 ,the 8observer0 need not be a mind1 but may be a photographic plate4 ,the peculiarities of the 8observer0 in this region belong to physics1 not to psychology4 ,so long as we continue to think in terms of bodies moving1 and try to adjust this way of thinking to the new ideas by successive corrections1 we shall only get more and more confused4 ,the only way to get clear is to make a fresh start1 with events instead of bodies4 ,in physics1 an 8event0 is anything which1 according to the old notions1 would be said to have both a date and a place4 ,an explosion1 a flash of lightning1 the starting of a light-wave from an atom1 the arrival of the light-wave at some other body1 any of these would be an 8event04 ,some strings of events make up what we regard as the history of one body2 some make up the course of one light-wave2 and so on4 ,the unity of a body is a unity of history--it is like the unity of a tune1 which takes time to play1 and does not exist whole in any one moment4 ,what exists at any one moment is only what we call an 8event04 ,it may be that the word 8event01 as used in physics1 cannot be quite identified with the same word as used in psychology2 for the present we are concerned with 8events0 as the constituents of physical processes1 and need not trouble ourselves about 8events0 in psychology4 ,the events in the physical world have relations to each other which are of the sort that have led to the notions of space and time4 ,they have relations of order1 so that we can say that one event is nearer to a second than to a third4 ,in this way we can arrive at the notion of the 8neighbourhood0 of an event3 it will consist roughly speaking of all the events that are very near the given event4 ,when we say that neighbouring events have a certain relation1 we shall mean that the nearer two events are to each other1 the more nearly they have this relation1 and that they approximate to having it without limit as they are taken nearer and nearer together4 ,two neighbouring events have a measurable quantitative relation called 8interval01 which is sometimes analogous to distance in space1 sometimes to lapse of time4 ,in the former case it is called space-like1 in the latter time-like4 ,the interval between two events is time-like when one body might be present at both--for example1 when both are parts of the history of your body4 ,the interval is space-like in the contrary case4 ,in the marginal case between the two1 the interval is zero2 this happens when both are parts of one light-ray4 ,the interval between two neighbouring events is something objective1 in the sense that any two careful observers will arrive at the same estimate of it4 ,they will not arrive at the same estimate for the distance in space or the lapse of time between the two events1 but the interval is a genuine physical fact1 the same for all4 ,if a body can travel freely from one event to the other1 the interval between the two events will be the same as the time between them as measured by a clock travelling with the body4 ,if such a journey is physically impossible1 the interval will be the same as the distance as estimated by an observer to whom the two events are simultaneous4 ,but the interval is only definite when the two events are very near together2 otherwise the interval depends upon the route chosen for travelling from the one event to the other4 ,four numbers are needed to fix the position of an event in the world2 these correspond to the time and the three dimensions of space in the old reckoning4 ,these four numbers are called the co-ordinates of the event4 ,they may be assigned on any principle which gives neighbouring co-ordinates to neighbouring events2 subject to this condition1 they are merely conventional4 ,for example1 suppose an aeroplane has had an accident4 ,you can fix the position of the accident by four numbers3 latitude1 longitude1 altitude above sea-level1 and ,greenwich ,mean ,time4 ,but you cannot fix the position of the explosion in space-time by means of less than four numbers4 ,everything in relativity-theory goes 7in a sense7 from next to next2 there are no direct relations between distant events1 such as distance in time or space4 ,and of course there are no forces acting at a distance2 in fact1 except as a convenient fiction1 there are no 8forces0 at all4 ,bodies take the course which is easiest at each moment1 according to the character of space-time in the particular region where they are2 this course is called a geodesic4 ,now it will be observed that ,i have been speaking freely of bodies and motion1 although ,i said that bodies were merely certain strings of events4 ,that being so1 it is of course necessary to say what strings of events constitute bodies1 since not all continuous strings of events do so1 not even all geodesics4 ,until we have defined the sort of thing that makes a body1 we cannot legitimately speak of motion1 since this involves the presence of one body on different occasions4 ,we must therefore set to work to define what we mean by the persistence of a body1 and how a string of events constituting a body differs from one which does not4 ,this topic will occupy the next chapter4 ,but it may be useful1 as a preliminary1 to teach our imagination to work in accordance with the new ideas4 ,we must give up what ,whitehead admirably calls the 8pushiness0 of matter4 ,we naturally think of an atom as being like a billiard-ball2 we should do better to think of it as like a ghost1 which has no 8pushiness0 and yet can make you fly4 ,we have to change our notions both of substance and of cause4 ,to say that an atom persists is like saying that a tune persists4 ,if a tune takes five minutes to play1 we do not conceive of it as a single thing which exists throughout that time1 but as a series of notes1 so related as to form a unity4 ,in the case of the tune1 the unity is sthetic2 in the case of the atom1 it is causal4 ,but when ,i say 8causal0 ,i do not mean exactly what the word naturally conveys4 ,there must be no idea of compulsion or 8force01 neither the force of contact which we imagine we see between billiard-balls nor the action at a distance which was formerly supposed to constitute gravitation4 ,there is merely an observed law of succession from next to next4 ,an event at one moment is succeeded by an event at a neighbouring moment1 which1 to the first order of small quantities1 can be calculated from the earlier event4 ,this enables us to construct a string of events1 each1 approximately1 growing out of a slightly earlier event according to an intrinsic law4 ,outside influences only affect the second order of small quantities4 ,a string of events connected1 in this way1 by an approximate intrinsic law of development is called one piece of matter4 ,this is what ,i mean by saying that the unity of a piece of matter is causal4 ,i shall explain this notion more fully in later chapters4 ,,chapter ,,xi ,,causal ,,laws ,,in ,,physics ,in the last chapter we spoke about the substitution of space-time for space and time1 and the effect which this has had in substituting strings of events for 8things0 conceived as substances4 ,in this chapter we will deal with cause and effect as they appear in the light of modern science4 ,it is at least as difficult to purge our imagination of irrelevances in this matter as in regard to substance4 ,the old-fashioned notion of cause appeared in dynamics as 8force04 ,we still speak of forces just as we still speak of the sunrise1 but we recognise that this is nothing but a convenient way of speaking1 in the one case as in the other4 ,causation is deeply embedded in language and common sense4 ,we say that people build houses or make roads3 to 8build0 and to 8make0 are both notions involving causality4 ,we say that a man is 8powerful01 meaning that his volitions are causes over a wide range4 ,some examples of causation seem to us quite natural1 others less so4 ,it seems natural that our muscles should obey our will1 and only reflection makes us perceive the necessity of finding an explanation of this phenomenon4 ,it seems natural that when you hit a billiard-ball with a cue it moves4 ,when we see a horse pulling a cart1 or a heavy object being dragged by a rope1 we feel as if we understood all about it4 ,it is events of this sort that have given rise to the common-sense belief in causes and forces4 ,but as a matter of fact the world is incredibly more complicated than it seems to common sense4 ,when we think we understand a process--,i mean by 8we0 the non-reflective part in each of us--what really happens is that there is some sequence of events so familiar through past experience that at each stage we expect the next stage4 ,the whole process seems to us peculiarly intelligible when human desires enter in1 for example1 in watching a game3 what the ball does and what the players do seem 8natural01 and we feel as if we quite understood how the stages succeed each other4 ,we thus arrive at the notion of what is called 8necessary0 sequence4 ,the text-books say that ,a is the cause of ,b if ,a is 8necessarily0 followed by ,b4 ,this notion of 8necessity0 seems to be purely anthropomorphic1 and not based upon anything that is a discoverable feature of the world4 ,things happen according to certain rules2 the rules can be generalised1 but in the end remain brute facts4 ,unless the rules are concealed conventions or definitions1 no reason can be given why they should not be completely different4 ,to say that ,a is 8necessarily0 followed by ,b is thus to say no more than that there is some general rule1 exemplified in a very large number of observed instances1 and falsified in none1 according to which events such as ,a are followed by events such as ,b4 ,we must not have any notion of 8compulsion01 as if the cause forced the effect to happen4 ,a good test for the imagination in this respect is the reversibility of causal laws4 ,we can just as often infer backwards as forwards4 ,when you get a letter1 you are justified in inferring that somebody wrote it1 but you do not feel that your receiving it compelled the sender to write it4 ,the notion of compulsion is just as little applicable to effects as to causes4 ,to say that causes compel effects is as misleading as to say that effects compel causes4 ,compulsion is anthropomorphic3 a man is compelled to do something when he wishes to do the opposite1 but except where human or animal wishes come in the notion of compulsion is inapplicable4 ,science is concerned merely with what happens1 not with what must happen4 ,when we look for invariable rules of sequence in nature1 we find that they are not such as common sense sets up4 ,common sense says3 thunder follows lightning1 waves at sea follow wind1 and so on4 ,rules of this sort are indispensable in practical life1 but in science they are all only approximate4 ,if there is any finite interval of time1 however short1 between the cause and the effect1 something may happen to prevent the effect from occurring4 ,scientific laws can only be expressed in differential equations4 ,this means that1 although you cannot tell what may happen after a finite time1 you can say that1 if you make the time shorter and shorter1 what will happen will be more and more nearly according to such-and-such a rule4 ,to take a very simple case3 ,i am now in this room2 you cannot tell where ,i shall be in another second1 because a bomb may explode and blow me sky-high1 but if you take any two small fragments of my body which are now very close together1 you can be sure that1 after some very short finite time1 they will still be very close together4 ,if a second is not short enough1 you must take a shorter time2 you cannot tell in advance how short a time you may have to take1 but you may feel fairly certain that there is a short enough time4 ,the laws of sequence in physics1 apart from quantum phenomena1 are of two sorts1 which appeared in traditional dynamics as laws of velocity and laws of acceleration4 ,in a very short time1 the velocity of a body alters very little1 and if the time is taken short enough1 the change of velocity diminishes without limit4 ,this is what1 in the last chapter1 we called an 8intrinsic0 causal law4 ,then there is the effect of the outer world1 as it appeared in traditional dynamics1 which is shown in acceleration4 ,the small change which does occur in the velocity in a short time is attributed to surrounding bodies1 because it is found to vary as they vary1 and to vary according to ascertained laws4 ,thus we think of surrounding bodies as exerting an influence1 which we call 8force01 though this remains as mysterious as the influence of the stars in astrology4 ,einstein's theory of gravitation has done away with this conception in so far as gravitational forces are concerned4 ,in this theory1 a planet moving round the sun is moving in the nearest approach to a straight line that the neighbourhood permits4 ,the neighbourhood is supposed to be non-,euclidean1 that is to say1 to contain no straight lines such as ,euclid imagined4 ,if a body is moving freely1 as the planets do1 it observes a certain rule4 ,perhaps the simplest way to state this rule is as follows3 ,suppose you take any two events which happen on the earth1 and you measure the time between them by ideally accurate clocks which move with the earth4 ,suppose some traveller on a magic carpet had meanwhile cruised about the universe1 leaving the earth at the time of the first event and returning at the time of the second4 ,by his clocks the period elapsed will be less than by the terrestial clocks4 ,this is what is meant by saying that the earth moves in a 8geodesic01 which is the nearest approach to a straight line to be found in the region in which we live4 ,all this is1 so to speak1 geometrical1 and involves no 8forces04 ,it is not the sun that makes the earth go round1 but the nature of space-time where the earth is4 ,even this is not quite correct4 ,space-time does not make the earth go round the sun2 it makes us say the earth goes round the sun4 ,that is to say1 it makes this the shortest way of describing what occurs4 ,we could describe it in other language1 which would be equally correct1 but less convenient4 ,the abolition of 8force0 in astronomy is perhaps connected with the fact that astronomy depends only upon the sense of sight4 ,on the earth1 we push and pull1 we touch things1 and we experience muscular strains4 ,this all gives us a notion of 8force01 but this notion is anthropomorphic4 ,to imagine the laws of motion of heavenly bodies1 think of the motions of objects in a mirror2 they may move very fast1 although in the mirror world there are no forces4 ,what we really have to substitute for force is laws of correlation4 ,events can be collected in groups by their correlations4 ,this is all that is true in the old notion of causality4 ,and this is not a 8postulate0 or 8category01 but an observed fact--lucky1 not necessary4 ,as we suggested before1 it is these correlations of events that lead to the definition of permanent 8things04 ,there is no essential difference1 as regards substantiality1 between an electron and a light-ray4 ,each is really a string of events or of sets of events4 ,in the case of the light-ray1 we have no temptation to think otherwise4 ,but in the case of the electron1 we think of it as a single persistent entity4 ,there may be such an entity1 but we can have no evidence that there is4 ,what we can discover is 7a7 a group of events spreading outwards from a centre--say1 for definiteness1 the events constituting a wave of light--and attributed1 hypothetically1 to a 8cause0 in that centre2 7b7 more or less similar groups of events at other times1 connected with the first group according to the laws of physics1 and therefore attributed to the same hypothetical cause at other times4 ,but all that we ought to assume is series of groups of events1 connected by discoverable laws4 ,these series we may define as 8matter04 ,whether there is matter in any other sense1 no one can tell4 ,what is true in the old notion of causality is the fact that events at different times are connected by laws 7differential equations74 ,when there is a law connecting an event ,a with an event ,b1 the two have a definite unambiguous time-order4 ,but if the events are such that a ray of light starting from ,a would arrive at any body which was present at ,b after ,b had occurred1 and vice versa1 then there is no definite true order1 and no possible causal law connecting ,a and ,b4 ,a and ,b must then be regarded as separate facts of geography4 ,perhaps the scope and purpose of this and the foregoing chapters may be made clearer by showing their bearing upon certain popular beliefs which may seem self-evident but are really in my opinion either false or likely to lead to falsehood4 ,i shall confine myself to objections which have actually been made to me when trying to explain the philosophical outcome of modern physics4#h #h ,these objections are quoted 7with kind permission7 from a letter written to me by a well-known engineer1 ,mr4 ,percy ,griffith1 who is also a writer on philosophical subjects4 8,we cannot conceive of movement apart from some thing as moving40 ,this is1 in a sense1 a truism2 but in the sense in which it is usually meant1 it is a falsehood4 ,we speak of the 8movement0 of a drama or piece of music1 although we do not conceive either as a 8thing0 which exists complete at every moment of the performance4 ,this is the sort of picture we must have in our minds when we try to conceive the physical world4 ,we must think of a string of events1 connected together by certain causal connections1 and having enough unity to deserve a single name4 ,we then begin to imagine that the single name denotes a single 8thing01 and if the events concerned are not all in the same place1 we say the 8thing0 has 8moved40 ,but this is only a convenient shorthand4 ,in the cinema1 we seem to see a man falling off a skyscraper1 catching hold of the telegraph wires1 and reaching the ground none the worse4 ,we know that1 in fact1 there are a number of different photographs1 and the appearance of a single 8thing0 moving is deceptive4 ,in this respect1 the real world resembles the cinema4 ,in connection with motion one needs to emphasise the very difficult distinction between experience and prejudice4 ,experience1 roughly1 is what you see1 and prejudice is what you only think you see4 ,prejudice tells you that you see the same table on two different occasions2 you think that experience tells you this4 ,if it really were experience1 you could not be mistaken2 yet a similar table may be substituted without altering the experience4 ,if you look at a table on two different occasions1 you have very similar sensations1 and memory tells you that they are similar2 but there is nothing to show that one identical entity causes the two sensations4 ,if the table is in a cinema1 you know that there is not such an entity1 even though you can watch it changing with apparent continuity4 ,the experience is just like that with a 8real0 table2 so in the case of a 8real0 table also1 there is nothing in the actual experience to show whether there is a persistent entity or not4 ,i say1 therefore3 ,i do not know whether there is a persistent entity1 but ,i do know that my experiences can be explained without assuming that there is4 ,therefore it can be no part of legitimate science to assert or deny the persistent entity2 if it does either1 it goes beyond the warrant of experience4 ,the following is a verbally cited passage in the letter referred to objecting to what was said above about 8force03 8,the concept of ,force is not of physical but of psychological origin4 ,rightly or wrongly it arises in the most impersonal contemplation of the ,stellar ,universe1 where we observe an infinite number of spherical bodies revolving on their own axes and gyrating in orbits round each other4 ,rightly or wrongly1 we naturally conceive of these as having been so constituted and so maintained by some ,force or ,forces40 ,we do not1 in fact1 8observe0 what it is here said that we observe2 all this is inferred4 ,what we observe1 in astronomy1 is a two-dimensional pattern of points of light1 with a few bright surfaces of measurable size when seen through the telescope 7the planets71 and of course the larger bright surfaces that we call the sun and moon4 ,most of this pattern 7the fixed stars7 rotates round the earth once in every twenty-three hours and fifty-six minutes4 ,the sun rotates in varying periods1 which average twenty-four hours and never departs very far from the average4 ,the moon and planets have apparent motions which are more irregular4 ,these are the observed facts4 ,there is no logical impossibility about the formul doctrine of spheres rotating round the earth1 one for each planet and one for the stars4 ,the modern doctrines are simpler1 but not one whit more in accordance with observed facts2 it is our passion for simple laws that has made us adopt them4 ,the last sentence of the above quotation raises some further points of interest4 8,rightly or wrongly01 the writer says1 8we naturally conceive of these as having been so constituted and so maintained by some ,force or ,forces40 ,i do not deny this4 ,it is 8natural01 and it is 8right or wrong0--more specifically1 it is wrong4 8,force0 is part of our love of explanations4 ,everyone knows about the ,hindu who thought that the world does not fall because it is supported by an elephant1 and the elephant does not fall because it is supported by a tortoise4 ,when his ,european interlocutor said 8,but how about the tortoise80 he replied that he was tired of metaphysics and wanted to change the subject4 8,force01 as an explanation1 is no better than the elephant and the tortoise4 ,it is an attempt to get at the 8why0 of natural processes1 not only at the 8how04 ,what we observe1 to a limited extent1 is what happens1 and we can arrive at laws according to which observable things happen1 but we cannot arrive at a reason for the laws4 ,if we invent a reason1 it needs a reason in its turn1 and so on4 8,force0 is a rationalising of natural processes1 but a fruitless one since 8force0 would have to be rationalised also4 ,when it is said1 as it often is1 that 8force0 belongs to the world of experience1 we must be careful to understand what can be meant4 ,in the first place1 it may be meant that calculations which employ the notion of force work out right in practice4 ,this1 broadly speaking1 is admitted3 no one would suggest that the engineer should alter his methods1 or should give up working out stresses and strains4 ,but that does not prove that there are stresses and strains4 ,a ,british medical man renders his accounts in guineas1 although they have long since ceased to exist except as a name2 he obtains a real payment1 though he employs a fictitious coin4 ,similarly1 the engineer is concerned with the question whether his bridge will stand3 the fact of experience is that it stands 7or does not stand71 and the stresses and strains are only a way of explaining what sort of bridge will stand4 ,they are as useful as guineas1 but equally imaginary4 ,but when it is said that force is a fact of experience1 there is something quite different that may be meant4 ,it may be meant that we experience force when we experience such things as pressure or muscular exertion4 ,we cannot discuss this contention adequately without going into the relation of physics to psychology1 which is a topic we shall consider at length at a later stage4 ,but we may say this much3 if you press your finger-tip upon a hard object1 you have an experience which you attribute to your finger-tip1 but there is a long chain of intermediate causes in nerves and brain4 ,if your finger were amputated you could still have the same experience by a suitable operation on the nerves that formerly connected the finger with the brain1 so that the force between the finger-tip and the hard object1 as a fact of experience1 may exist when there is no finger-tip4 ,this shows that force1 in this sense1 cannot be what concerns physics4 ,as the above example illustrates1 we do not1 in fact1 experience many things that we think we experience4 ,this makes it necessary to ask1 without too much assurance1 in what sense physics can be based upon experience1 and what must be the nature of its entities and its inferences if it is to make good its claim to be empirically grounded4 ,we shall begin this inquiry in the next chapter4 ,,chapter ,,xii ,,physics ,,and ,,perception ,it will be remembered that we regarded perception1 in ,chapter ,v1 as a species of 8sensitivity04 ,sensitivity to a given feature of the environment we defined as consisting in some characteristic reaction which is exhibited whenever that feature is present1 but not otherwise2 this property is possessed more perfectly1 in given directions1 by scientific instruments than by living bodies1 though scientific instruments are more selective as to the stimuli to which they will respond4 ,we decided that what1 from the standpoint of an external observer1 distinguishes perception from other forms of sensitivity is the law of association or conditioned reflexes4 ,but we also found that this purely external treatment of perception presupposes our knowledge of the physical world as a going concern4 ,we have now to investigate this presupposition1 and to consider how we come to know about physics1 and how much we really do know4 ,according to the theory of ,chapter ,v1 it is possible to perceive things that are not in a spatial contact with the body4 ,there must be a reaction to a feature of the environment1 but that feature may be at a greater or less distance from the body of the percipient2 we can even perceive the sun and stars1 within the limits of the definition4 ,all that is necessary is that our reaction should depend upon the spatial relation between our body and the feature of the environment4 ,when our back is towards the sun1 we do not see it2 when our face is towards it1 we do4 ,when we consider perception--visual or auditory--of an external event1 there are three different matters to be examined4 ,there is first the process in the outside world1 from the event to the percipient's body2 there is next the process in his body1 in so far as this can be known by an outside observer2 lastly1 there is the question1 which must be faced sooner or later1 whether the percipient can perceive something of the process in his body which no other observer could perceive4 ,we will take these points in order4 ,if it is to be possible to 8perceive0 an event not in the percipient's body1 there must be a physical process in the outer world such that1 when a certain event occurs1 it produces a stimulus of a certain kind at the surface of the percipient's body4 ,suppose1 for example1 that pictures of different animals are exhibited on a magic lantern to a class of children1 and all the children are asked to say the name of each animal in turn4 ,we may assume that the children are sufficiently familiar with animals to say 8cat01 8dog01 8giraffe01 8hippopotamus01 etc41 at the right moments4 ,we must then suppose--taking the physical world for granted--that some process travels from each picture to the eyes of the various children1 retaining throughout these journeys such peculiarities that1 when the process reaches their eyes1 it can in one case stimulate the word 8cat0 and in another the word 8dog04 ,all this the physical theory of light provides for4 ,but there is one interesting point about language that should be noticed in this connection4 ,if the usual physical theory of light is correct1 the various children will receive stimuli which differ greatly according to their distance and direction from the picture1 and according to the way the light falls4 ,there are also differences in their reactions1 for1 though they all utter the word 8cat01 some say it loud1 others soft1 some in a soprano voice1 some in a contralto4 ,but the differences in their reactions are much less than the differences in the stimuli4 ,this is still more the case if we consider various different pictures of cats1 to all of which they respond with the word 8cat04 ,thus language is a means of producing responses which differ less than the stimuli do1 in cases where the resemblances between the stimuli are more important to us than the differences4 ,this fact makes us apt to overlook the differences between stimuli which produce nearly identical responses4 ,as appears from the above1 when a number of people simultaneously perceive a picture of a cat1 there are differences between the stimuli to their various perceptions1 and these differences must obviously involve differences in their reactions4 ,the verbal responses may differ very little1 but even the verbal responses could be made to differ by putting more complicated questions than merely 8,what animal is that80 ,one could ask3 8,can the picture be covered by your thumb-nail held at arm's length80 ,then the answer would be different according as the percipient was near the picture or far off4 ,but the normal percipient1 if left to himself1 will not notice such differences1 that is to say1 his verbal response will be the same in spite of the differences in the stimuli4 ,the fact that it is possible for a number of people to perceive the same noise or the same coloured pattern obviously depends upon the fact that a physical process can travel outward from a centre and retain certain of its characteristics unchanged1 or very little changed4 ,the most notable of such characteristics is frequency in a wave-motion4 ,that1 no doubt1 affords a biological reason for the fact that our most delicate senses1 sight and hearing1 are sensitive to frequencies1 which determine colour in what we see and pitch in what we hear4 ,if there were not1 in the physical world1 processes spreading out from centres and retaining certain characters practically unchanged1 it would be impossible for different percipients to perceive the same object from different points of view1 and we should not have been able to discover that we all live in a common world4 ,we come now to the process in the percipient's body1 in so far as this can be perceived by an outside observer4 ,this raises no new philosophical problems1 because we are still concerned1 as before1 with the perception of events outside the observer's body4 ,the observer1 now1 is supposed to be a physiologist1 observing1 say1 what goes on in the eye when light falls upon it4 ,his means of knowing are1 in principle1 exactly the same as in the observation of dead matter4 ,an event in an eye upon which light is falling causes light-waves to travel in a certain manner until they reach the eye of the physiologist4 ,they there cause a process in the physiologist's eye and optic nerve and brain1 which ends in what he calls 8seeing what happens in the eye he is observing04 ,but this event1 which happens in the physiologist1 is not what happened in the eye he was observing2 it is only connected with this by a complicated causal chain4 ,thus our knowledge of physiology is no more direct or intimate than our knowledge of processes in dead matter2 we do not know any more about our eyes than about the trees and fields and clouds that we see by means of them4 ,the event which happens when a physiologist observes an eye is an event in him1 not on the eye that he is observing4 ,we come now at last to the question of self-observation1 which we have hitherto avoided4 ,i say 8self-observation0 rather than 8introspection01 because the latter word has controversial associations that ,i wish to avoid4 ,i mean by 8self-observation0 anything that a man can perceive about himself but that others1 however situated1 cannot perceive about him4 ,what follows is only preliminary1 since the subject will be discussed at length in ,chapter ,,xvi4 ,no one can deny that we know things about ourselves which others cannot know unless we tell them4 ,we know when we have toothache1 when we feel thirsty1 what we were dreaming when we woke up1 and so on4 ,dr4 ,watson might say that the dentist can know we have toothache by observing a cavity in a tooth4 ,i will not reply that the dentist is often mistaken2 this may be merely because the art of dentistry has not been sufficiently perfected4 ,i will concede as possible1 in the future1 a state of odontology in which the dentist could always know whether ,i am feeling toothache4 ,but even then his knowledge has a different character from mine4 ,his knowledge is an inference1 based upon the inducive law that people with such-and-such cavities suffer pain of a certain kind4 ,but this law cannot be established by observation of cavities alone2 it requires that1 where these are observed1 the people who have them should tell us that they feel toothache4 ,and1 more than that1 they must be speaking the truth4 ,purely external observation can discover that people with cavities say they have toothache1 but not that they have it4 ,saying one has toothache is a different thing from having it2 if not we could cure toothache by not talking about it1 and so save our dentists' bills4 ,i am sure the expert opinion of dentists will agree with me that this is impossible4 ,to this argument1 however1 it might be replied that having toothache is a state of the body1 and that knowing ,i have toothache is a response to this bodily stimulus4 ,it will be said that1 theoretically1 the state of my body when ,i have toothache can be observed by an outsider1 who can then also know that ,i have toothache4 ,this answer1 however1 does not really meet the point4 ,when the outside observer knows that ,i have toothache1 not only is his knowledge based upon an inductive inference1 as we have already seen1 but his knowledge of the inferred term1 8toothache01 must be based upon personal experience4 ,no knowledge of dentistry could enable a man to know what toothache is if he had never felt it4 ,if1 then1 toothache is really a state of the body--which1 at the moment1 ,i neither affirm nor deny--it is a state of the body which only the man himself can perceive4 ,in a word1 whoever has experienced toothache and can remember it has knowledge that cannot be possessed by a man who has never experienced toothache4 ,take next our knowledge of our own dreams4 ,dr4 ,watson has not1 so far as ,i know1 ever discussed dreams1 but ,i imagine he would say something like this3 ,in dreams1 there are probably small laryngeal movements such as1 if they were greater1 would lead to speech2 indeed1 people do sometimes cry out in dreams4 ,there may also be stimulations of the sense-organs1 which produce unusual reactions owing to the peculiar physiological condition of the brain during sleep3 but all these reactions must consist of small movements1 which could theoretically be seen from outside1 say by some elaboration of ,x-ray apparatus4 ,this is all very well1 but meantime it is hypothetical1 and the dreamer himself knows his dreams without all this elaborate inference4 ,can we say that he really knows these hypothetical small bodily movements1 although he thinks he knows something else8 ,that would presumably be ,dr4 ,watson's position1 and it must be admitted that1 with a definition of 8knowledge0 such as we considered in ,chapter ,,viii1 such a view is not to be dismissed offhand as obviously impossible4 ,moreover1 if we are to say the perception gives knowledge of the physical world1 we shall have to admit that what we are perceiving may be quite different from what it seems to be4 ,a table does not look like a vast number of electrons and protons1 nor like trains of waves meeting and clashing4 ,yet this is the sort of thing a table is said to be by modern physicists4 ,if1 then1 what seems to us to be just a table such as may be seen any day is really this odd sort of thing1 it is possible that what seems to us to be a dream is really a number of movements in the brain4 ,this again is all very well1 but there is one point which it fails to explain1 namely1 what is meant by 8seeming04 ,if a dream or a table 8seems0 to be one sort of thing while it is 8really0 another1 we shall have to admit that it really seems1 and that what it seems to be has a reality of its own4 ,nay more1 we only arrive at what it 8really0 is by an inference1 valid or invalid1 from what it seems to be4 ,if we are wrong about the seeming1 we must be doubly wrong about the reality1 since the sole ground for asserting the table composed of electrons and protons is the table that we see1 i4e4 the 8seeming0 table4 ,we must therefore treat 8seeming0 with respect4 ,let us consider ,dr4 ,watson watching a rat in a maze4 ,he means to be quite objective1 and report only what really goes on4 ,can he succeed8 ,in one sense he can4 ,he can use words about what he sees which are the same as any other scientifically trained observer will use if he watches the same rat at the same time4 ,but ,dr4 ,watson's objectivity emphatically does not consist in using the same words as other people use2 his vocabulary is very different from that of most psychologists4 ,he cannot take as the sole test of truth the consensus of mankind4 8,securus judicat orbis terrarum0 is another example of a ,latin tag which is false1 and which certainly ,dr4 ,watson would not consider true4 ,it has happened again and again in human history that a man who said something that had never been said before turned out to be right1 while the people who repeated the wise saws of their forefathers were talking nonsense4 ,therefore1 when ,dr4 ,watson endeavours to eliminate subjectivity in observing rats1 he does not mean that he says what everybody else says4 ,he means that he refrains from inferring anything about the rat beyond its bodily movements4 ,this is all to the good1 but ,i think he fails to realise that almost as long and difficult an inference is required to give us knowledge of the rat's bodily movements as to give us knowledge of its 8mind04 ,and what is more1 the data from which we must start in order to get to know the rat's bodily movements are data of just the sort that ,dr4 ,watson wishes to avoid1 namely private data patent to self-observation but not patent to anyone except the observer4 ,this is the point at which1 in my opinion1 behaviourism as a final philosophy breaks down4 ,when several people simultaneously watch a rat in a maze1 or any other example of what we should naturally regard as matter in motion1 there is by no means complete identity between the physical events which happen at the surface of their eyes and constitute the stimuli to their perceptions4 ,there are differences of perspective1 of light and shade1 of apparent size1 and so on1 all of which will be reproduced in photographs taken from the places where the eyes of the several observers are4 ,these differences produce differences in the reactions of the observers--differences which a quite unthinking person may overlook1 but which are familiar to every artist4 ,now it is contrary to all scientific canons to suppose that the object perceived1 in addition to affecting us in the way of stimulus and reaction1 also affects us directly by some mystical epiphany2 certainly it is not what any behaviourist would care to assert4 ,our knowledge of the physical world1 therefore1 must be contained in our reaction to the stimulus which reaches us across the intervening medium2 and it seems hardly possible that our reaction should have a more intimate relation to the object than the stimulus has4 ,since the stimulus differs for different observers1 the reaction also differs2 consequently1 in all our perceptions of physical processes there is an element of subjectivity4 ,if1 therefore1 physics is true in its broad outlines 7as the above argument supposes71 what we call 8perceiving0 a physical process is something private and subjective1 at least in part1 and is yet the only possible starting-point for our knowledge of the physical world4 ,there is an objection to the above argument which might naturally be made1 but it would be in fact invalid4 ,it may be said that we do not in fact proceed to infer the physical world from our perceptions1 but that we begin at once with a rough-and-ready knowledge of the physical world1 and only at a late stage of sophistication compel ourselves to regard our knowledge of the physical world as an inference4 ,what is valid in this statement is the fact that our knowledge of the physical world is not at first inferential1 but that is only because we take our percepts to be the physical world4 ,sophistication and philosophy come in at the stage at which we realise that the physical world cannot be identified with our percepts4 ,when my boy was three years old1 ,i showed him ,jupiter1 and told him that ,jupiter was larger than the earth4 ,he insisted that ,i must be speaking of some other ,jupiter1 because1 as he patiently explained1 the one he was seeing was obviously quite small4 ,after some efforts1 ,i had to give it up and leave him unconvinced4 ,in the case of the heavenly bodies1 adults have got used to the idea that what is really there can only be inferred from what they see2 but where rats in mazes are concerned1 they still tend to think that they are seeing what is happening in the physical world4 ,the difference1 however1 is only one of degree1 and naive realism is as untenable in the one case as in the other4 ,there are differences in the perceptions of two persons observing the same process2 there are sometimes no discoverable differences between two perceptions of the same persons observing different processes1 e4g4 pure water and water full of bacilli4 ,the subjectivity of our perceptions is thus of practical as well as theoretical importance4 ,i am not maintaining that what we primarily know is our own perceptions4 ,this is largely a verbal question2 but with the definition of knowledge given in ,chapter ,,viii1 it will be correct to say that from the first we know external objects1 the question is not as to what are the objects we know1 but rather as to how accurately we know them4 ,our non-inferential knowledge of an object cannot be more accurate than our reaction to it1 since it is part of that reaction4 ,and our reaction cannot be more accurate than the stimulus4 ,but what on earth can you mean by the 8accuracy0 of a stimulus8 ,i may be asked4 ,i mean just the same as by the accuracy of a map or a set of statistics4 ,i mean a certain kind of correspondence4 ,one pattern is an accurate representation of another if every element of the one can be taken as the representative of just one element of the other1 and the relations that make the one set into a pattern correspond with relations making the other set into a pattern4 ,in this sense1 writing can represent speech with a certain degree of accuracy2 to every spoken word a written word corresponds1 and to the time-order of the spoken words the space-order of the written words corresponds4 ,but there are inflexions and tones of voice that cannot be represented in writing1 except1 to some extent1 by musical notation4 ,a gramophone record is a much more accurate representation of vocal sounds than any writing can be2 but even the best gramophone record fails to be completely accurate4 ,the impression made upon an observer is very analogous to a gramophone record or a photograph1 but usually less accurate owing to the influence of the law of association1 and the lack of delicacy in our senses4 ,and whatever limitations there are to the accuracy of our impressions are limitations to the accuracy of our non-inferential knowledge of the external world4 ,another point3 ,if we accept the definition of knowledge given in ,chapter ,,viii1 which was framed so far as to be as favourable as possible to behaviourism1 a given reaction may be regarded as knowledge of various different occurrences4 ,when we see ,jupiter1 we have1 according to the definition1 knowledge of ,jupiter1 but we also have knowledge of the stimulus at the surface of the eye1 and even of the process in the optic nerve4 ,for it is arbitrary at what point we start in the process leading to a certain event in the brain3 this event1 and the consequent bodily action1 may be regarded as a reaction to a process starting at any earlier point4 ,and the nearer our starting-point is to the brain1 the more accurate becomes the knowledge displayed in our reaction4 ,a lamp at the top of a tall building might produce the same visual stimulus as ,jupiter1 or at any rate one practically indistinguishable from that produced by ,jupiter4 ,a blow on the nose might make us 8see stars04 ,theoretically1 it should be possible to apply a stimulus direct to the optic nerve1 which should give us a visual sensation4 ,thus when we think we see ,jupiter1 we may be mistaken4 ,we are less likely to be mistaken if we say that the surface of the eye is being stimulated in a certain way1 and still less likely to be mistaken if we say that the optic nerve is being stimulated in a certain way4 ,we do not eliminate the risk of error completely unless we confine ourselves to saying that an event of a certain sort is happening in the brain2 this statement may still be true if we see ,jupiter in a dream4 ,but1 ,i shall be asked1 what do you know about what is happening in the brain8 ,surely nothing4 ,not so1 ,i reply4 ,i know about what is happening in the brain exactly what naive realism thinks it knows about what is happening in the outside world4 ,but this needs explaining1 and there are other matters that must be explained first4 ,when the light from a fixed star reaches me1 ,i see the star if it is night and ,i am looking in the right direction4 ,the light started years ago1 probably many years ago1 but my reaction is primarily to something that is happening now4 ,when my eyes are open1 ,i see the star2 when they are shut1 ,i do not4 ,children discover at a fairly early age that they see nothing when their eyes are shut4 ,they are aware of the difference between seeing and not seeing1 and also of the difference between eyes open and eyes shut2 gradually they discover that these two differences are correlated--,i mean that they have expectations of which this is the intellectualist transcription4 ,again1 children learn to name the colours1 and to state correctly whether a thing is blue or red or yellow or what-not4 ,they ought not to be sure that light of the appropriate wave-length started from the object4 ,the sun looks red in a ,london fog1 grass looks blue through blue spectacles1 everything looks yellow to a person suffering from jaundice4 ,but suppose you ask3 ,what colour are you seeing8 ,the person who answers1 in these cases1 red for the sun1 blue for the grass1 and yellow for the sick-room of the jaundiced patient1 is answering quite truly4 ,and in each of these cases he is stating something that he knows4 ,what he knows in such cases is what ,i call a 8percept04 ,i shall contend later that1 from the standpoint of physics1 a percept is in the brain2 for the present1 ,i am only concerned to say that a percept is what is most indubitable in our knowledge of the world4 ,to behaviourism as a metaphysic one may put the following dilemma4 ,either physics is valid in its main lines1 or it is not4 ,if it is not1 we know nothing about the movements of matter2 for physics is the result of the most serious and careful study of which the human intelligence has hitherto been capable4 ,if1 on the other hand1 physics is valid in its main lines1 any physical process starting either inside or outside the body will1 if it reaches the brain1 be different if the intervening medium is different2 moreover two persons1 initially very different1 may become indistinguishable as they spread and grow fainter4 ,on both grounds1 what happens in the brain is not connected quite accurately with what happens elsewhere1 and our perceptions are therefore infected with subjectivity on purely physical grounds4 ,even1 therefore1 when we assume the truth of physics1 what we know most indubitably through perception is not the movements of matter1 but certain events in ourselves which are connected1 in a manner not quite invariable1 with the movements of matter4 ,to be specific1 when ,dr4 ,watson watches rats in mazes1 what he knows1 apart from difficult inferences1 are certain events in himself4 ,the behaviour of the rats can only be inferred by the help of physics1 and is by no means to be accepted as something accurately knowable by direct observation4 ,i do not in fact entertain any doubts that physics is true in its main lines4 ,the interpretation of physical formul is a matter as to which a considerable degree of uncertainty is possible2 but we cannot well doubt that there is an interpretation which is true roughly and in the main4 ,i shall come to the question of interpretation later2 for the present1 ,i shall assume that we may accept physics in its broad outlines1 without troubling to consider how it is to be interpreted4 ,on this basis1 the above remarks on perception seem undeniable4 ,we are often misled as to what is happening1 either by peculiarities of the medium between the object and our bodies1 or by unusual states of our bodies1 or by a temporary or permanent abnormality in the brain4 ,but in all these cases something is really happening1 as to which1 if we turn our attention to it1 we can obtain knowledge that is not misleading4 ,at one time when1 owing to illness1 ,i had been taking a great deal of quinine1 ,i became hypersensitive to noise1 so that when the nurse rustled the newspaper ,i thought she was spilling a scuttle of coals on the floor4 ,the interpretation was mistaken1 but it was quite true that ,i heard a loud noise4 ,it is a commonplace that a man whose leg has been amputated can still feel pains in it2 here again1 he does really feel the pains1 and is only mistaken in his belief that they come from his leg4 ,a percept is an observable event1 but its interpretation as knowledge of this or that event in the physical world is liable to be mistaken1 for reasons which physics and physiology can make fairly clear4 ,the subjectivity of percepts is a matter of degree4 ,they are more subjective when people are drunk or asleep than when they are sober and awake4 ,they are more subjective in regard to distant objects than in regard to such as are near4 ,they may acquire various peculiar kinds of subjectivity through injuries to the brain or to the nerves4 ,when ,i speak of a percept as 8subjective0 ,i mean that the physiological inferences to which it gives rise are mistaken or vague4 ,this is always the case to some extent1 but much more so in some circumstances than in others4 ,and the sort of defect that leads to mistakes must be distinguished from the sort that leads to vagueness4 ,if you see a man a quarter of a mile away1 you can see that it is a man if you have normal eyesight1 but you probably cannot tell who it is1 even if in fact it is some one you know well4 ,this is vagueness in the percept3 the inferences you draw are correct so far as they go1 but they do not go very far4 ,on the other hand1 if you are seeing double and think there are two men1 you have a case of mistake4 ,vagueness1 to a greater or less extent1 is universal and inevitable2 mistakes1 on the other hand1 can usually be avoided by taking trouble and by not always trusting to physiological inference4 ,anybody can see double on purpose1 by focussing on a distant object and noticing a near one2 but this will not cause mistakes1 since the man is aware of the subjective element in his double vision4 ,similarly we are not deceived by after-images1 and only dogs are deceived by gramophones4 ,from what has been said in this chapter1 it is clear that our knowledge of the physical world1 if it is to be made as reliable as possible1 must start from percepts1 and must scrutinize the physiological inferences by which percepts are accompanied4 ,physiological inference is inference in the sense that it sometimes leads to error and physics gives reason to expect that percepts will1 in certain circumstances1 be more or less deceptive if taken as signs of something outside the brain4 ,it is these facts that give a subjective cast to the philosophy of physics1 at any rate in its beginnings4 ,we cannot start cheerfully with a world of matter in motion1 as to which any two sane and sober observers must agree4 ,to some extent1 each man dreams his own dream1 and the disentangling of the dream element in our percepts is no easy matter4 ,this is1 indeed1 the work that scientific physics undertakes to do4 ,,chapter ,,xiii ,,physical ,,and ,,perceptual ,,space ,perhaps there is nothing so difficult for the imagination as to teach it to feel about space as modern science compels us to think4 ,this is the task which must be attempted in the present chapter4 ,we said in ,chapter ,,xii that we know about what is happening in the brain exactly what naive realism thinks it knows about what is happening in the world4 ,this remark may have seemed cryptic2 it must now be expanded and expounded4 ,the gist of the matter is that percepts1 which we spoke about at the end of last chapter1 are in our heads2 that percepts are what we can know with most certainty2 and that percepts contain what naive realism thinks it knows about the world4 ,but when ,i say that my percepts are in my head1 ,i am saying something which is ambiguous until the different kinds of space have been explained1 for the statement is only true in connection with physical space4 ,there is also a space in our percepts1 and of this space the statement would not be true4 ,when ,i say that there is space in our percepts1 ,i mean nothing at all difficult to understand4 ,i mean--to take the sense of sight1 which is the most important in this connection--that in what we see at one time there is up and down1 right and left1 inside and outside4 ,if we see1 say1 a circle on a blackboard1 all these relations exist within what we see4 ,the circle has a top half and a bottom half1 a right-hand half and a left-hand half1 an inside and an outside4 ,those relations alone are enough to make up a space of sorts4 ,but the space of everyday life is filled out with what we derive from touch and movement--how a thing feels when we touch it1 and what movements are necessary in order to grasp it4 ,other elements also come into the genesis of the space in which everybody believes who has not been troubled by philosophy2 but it is unnecessary for our purposes to go into this question any more deeply4 ,the point that concerns us is that a man's percepts are private to himself3 what ,i see1 no one else sees2 what ,i hear1 no one else hears2 what ,i touch1 no one else touches2 and so on4 ,true1 others hear and see something very like what ,i hear and see1 if they are suitably placed2 but there are always differences4 ,sounds are less loud at a distance2 objects change their visual appearance according to the laws of perspective4 ,therefore it is impossible for two persons at the same time to have exactly identical percepts4 ,it follows that the space of percepts1 like the percepts1 must be private2 there are as many perceptual spaces as there are percipients4 ,my percept of a table is outside my percept of my head1 in my perceptual space2 but it does not follow that it is outside my head as a physical object in physical space4 ,physical space is neutral and public3 in this space1 all my percepts are in my head1 even the most distant star as ,i see it4 ,physical and perceptual space have relations1 but they are not identical1 and failure to grasp the difference between them is a potent source of confusion4 ,to say that you see a star when you see the light that has come from it is no more correct than to say that you see ,new ,zealand when you see a ,new ,zealander in ,london4 ,your perception when 7as we say7 you see a star is causally connected1 in the first instance1 with what happens in the brain1 the optic nerve1 and the eye1 then with a light-wave which1 according to physics1 can be traced back to the star as its source4 ,your sensations will be closely similar if the light comes from a lamp at the top of a mast4 ,the physical space in which you believe the 8real0 star to be is an elaborate inference2 what is given is the private space in which the speck of light you see is situated4 ,it is still an open question whether the space of sight has depth1 or is merely a surface1 as ,berkeley contended4 ,this does not matter for our purposes4 ,even if we admit that sight alone shows a difference between an object a few inches from the eyes and an object several feet distant1 yet you certainly cannot1 by sight alone1 see that a cloud is less distant than a fixed star1 though you may infer that it is1 because it can hide the star4 ,the world of astronomy1 from the point of view of sight1 is a surface4 ,if you were put in a dark room with little holes cut in the ceiling in the pattern of the stars letting light come through1 there would be nothing in your immediate visual data to show that you were not 8seeing the stars04 ,this illustrates what ,i mean by saying that what you see is not 8out there0 in the sense of physics4 ,we learn in infancy that we can sometimes touch objects we see1 and sometimes not4 ,when we cannot touch them at once1 we can sometimes do so by walking to them4 ,that is to say1 we learn to correlate sensations of sight with sensations of touch1 and sometimes with sensations of movement followed by sensations of touch4 ,in this way we locate our sensations in a three-dimensional world4 ,those which involve sight alone we think of as 8external01 but there is no justification for this view4 ,what you see when you see a star is just as internal as what you feel when you feel a headache4 ,that is to say1 it is internal from the standpoint of physical space4 ,it is distant in your private space1 because it is not associated with sensations of touch1 and cannot be associated with them by means of any journey you can perform4 ,your own body1 as known to you through direct experience1 is quite different from your own body as considered in physics4 ,you know more about your own body than about any other through direct experience1 because your own body can give you a number of sensations that no other body can1 for instance all kinds of bodily pains4 ,but you still know it only through sensations2 apart from inference1 it is a bundle of sensations1 and therefore quite different1 prima facie1 from what physics calls a body4 ,most of the things you see are outside what you see when 7as one says7 you see your own body4 ,that is to say3 you see certain other patches of colour1 differently situated in visual space1 and say you are seeing things outside your body4 ,but from the point of view of physics1 all that you see must count as inside your body2 what goes on elsewhere can only be inferred4 ,thus the whole space of your sensible world with all its percepts counts as one tiny region from the point of view of physics4 ,there is no direct spatial relation between what one person sees and what another sees1 because no two ever see exactly the same object4 ,each person carries about a private space of his own1 which can be located in physical space by indirect methods1 but which contains no place in common with another person's private space4 ,this shows how entirely physical space is a matter of inference and construction4 ,to make the matter definite1 let us suppose that a physiologist is observing a living brain--no longer an impossible supposition1 as it would have been formerly4 ,it is natural to suppose that what the physiologist sees is in the brain he is observing4 ,but if we are speaking of physical space1 what the physiologist sees is in his own brain4 ,it is in no sense in the brain that he is observing1 though it is in the percept of that brain1 which occupies part of the physiologist's perceptual space4 ,causal continuity makes the matter perfectly evident3 light-waves travel from the brain that is being observed to the eye of the physiologist1 at which they only arrive after an interval of time1 which is finite though short4 ,the physiologist sees what he is observing only after the light-waves have reached his eye2 therefore the event which constitutes his seeing comes at the end of a series of events which travel from the observed brain into the brain of the physiologist4 ,we cannot1 without a preposterous kind of discontinuity1 suppose that the physiologist's percept1 which comes at the end of this series1 is anywhere else but in the physiologist's head4 ,this question is very important1 and must be understood if metaphysics is ever to be got straight4 ,the traditional dualism of mind and matter1 which ,i regard as mistaken1 is intimately connected with confusions on this point4 ,so long as we adhere to the conventional notions of mind and matter1 we are condemned to a view of perception which is miraculous4 ,we suppose that a physical process starts from a visible object1 travels to the eye1 there changes into another physical process1 causes yet another physical process in the optic nerve1 finally produces some effect in the brain1 simultaneously with which we see the object from which the process started1 the seeing being something 8mental01 totally different in character from the physical processes which precede and accompany it4 ,this view is so queer that metaphysicians have invented all sorts of theories designed to substitute something less incredible4 ,but nobody noticed an elementary confusion4 ,to return to the physiologist observing another man's brain3 what the physiologist sees is by no means identical with what happens in the brain he is observing1 but is a somewhat remote effect4 ,from what he sees1 therefore1 he cannot judge whether what is happening in the brain he is observing is1 or is not1 the sort of event that he would call 8mental04 ,when he says that certain physical events in the brain are accompanied by mental events1 he is thinking of physical events as if they were what he sees4 ,he does not see a mental event in the brain he is observing1 and therefore supposes there is in that brain a physical process which he can observe and a mental process which he cannot4 ,this is a complete mistake4 ,in the strict sense1 he cannot observe anything in the other brain1 but only the percepts which he himself has when he is suitably related to that brain 7eye to microscope1 etc474 ,we first identify physical processes with our percepts1 and then1 since our percepts are not other people's thoughts1 we argue that the physical processes in their brains are something quite different from their thoughts4 ,in fact1 everything that we can directly observe of the physical world happens inside our heads1 and consists of 8mental0 events in at least one sense of the word 8mental04 ,it also consists of events which form part of the physical world4 ,the development of this point of view will lead us to the conclusion that the distinction between mind and matter is illusory4 ,the stuff of the world may be called physical or mental or both or neither1 as we please2 in fact1 the words serve no purpose4 ,there is only one definition of the words that is unobjectionable3 8physical0 is what is dealt with by physics1 and 8mental0 is what is dealt with by psychology4 ,when1 accordingly1 ,i speak of 8physical0 space1 ,i mean the space that occurs in physics4 ,it is extraordinarily difficult to divest ourselves of the belief that the physical world is the world we perceive by sight and touch2 even if1 in our philosophic moments1 we are aware that this is an error1 we nevertheless fall into it again as soon as we are off our guard4 ,the notion that what we see is 8out there0 in physical space is one which cannot survive while we are grasping the difference between what physics supposes to be really happening1 and what our senses show us as happening2 but it is sure to return and plague us when we begin to forget the argument4 ,only long reflection can make a radically new point of view familiar and easy4 ,our illustrations hitherto have been taken from the sense of sight2 let us now take one from the sense of touch4 ,suppose that1 with your eyes shut1 you let your finger-tip press against a hard table4 ,what is really happening8 ,the physicist says that your finger-tip and the table consist1 roughly speaking1 of vast numbers of electrons and protons2 more correctly1 each electron and proton is to be thought of as a collection of processes of radiation1 but we can ignore this for our present purposes4 ,although you think you are touching the table1 no electron or proton in your finger ever really touches an electron or proton in the table1 because this would develop an infinite force4 ,when you press1 repulsions are set up between parts of your finger and parts of the table4 ,if you try to press upon a liquid or a gas1 there is room in it for the parts that are repelled to get away4 ,but if you press a hard solid1 the electrons and protons that try to get away1 because electrical forces from your finger repel them1 are unable to do so1 because they are crowded close to others which elbow them back to more or less their original position1 like people in a dense crowd4 ,therefore the more you press the more they repel your finger4 ,the repulsion consists of electrical forces1 which set up in the nerves a current whose nature is not very definitely known4 ,this current runs into the brain1 and there has effects which1 so far as the physiologist is concerned1 are almost wholly conjectural4 ,but there is one effect which is not conjectural1 and that is the sensation of touch4 ,this effect1 owing to physiological inference or perhaps to a reflex1 is associated by us with the finger-tip4 ,but the sensation is the same if1 by artificial means1 the parts of the nerve nearer the brain are suitably stimulated--e4g4 if your hand has been amputated and the right nerves are skilfully manipulated4 ,thus our confidence that touch affords evidence of the existence of bodies at the place which we think is being touched is quite misplaced4 ,as a rule we are right1 but we can be wrong2 there is nothing of the nature of an infallible revelation about the matter4 ,and even in the most favorable case1 the perception of touch is something very different from the mad dance of electrons and protons trying to jazz out of each other's way1 which is what physics maintains is really taking place at your finger-tip4 ,or1 at least1 it seems very different4 ,but as we shall see1 the knowledge we derive from physics is so abstract that we are not warranted in saying that what goes on in the physical world is1 or is not1 intrinsically very different from the events that we know through our own experiences4 ,,chapter ,,xiv ,,perception ,,and ,,physical ,,causal ,,laws ,in an earlier chapter we saw the inadequacy of the traditional notion of cause1 without adequately explaining the causal laws which are a substitute in the practice of science4 ,the time has now come when it is possible to remedy this defect1 and1 in so doing1 to fit perception into its place in the chain of physical causation and recapitulate the main points of previous arguments4 ,the old view was that an event ,a will always be followed by a certain event ,b1 and that the problem of discovering causal laws is the problem1 given an event ,b1 of finding that event ,a which is its invariable antecedent or vice versa4 ,at an early stage of a science this point of view is useful2 it gives laws which are true usually1 though probably not always1 and it affords the basis for more exact laws4 ,but it has no philosophical validity1 and is superseded in science as soon as we arrive at genuine laws4 ,genuine laws1 in advanced sciences1 are practically always quantitative laws of tendency4 ,i will try to illustrate by taking the simplest possible case in physics4 ,imagine a hydrogen atom1 in which the electron is revolving not in the minimum orbit1 but in the next1 which has four times the minimum radius4 ,so long as this state continues1 the atom has no external effects1 apart from its infinitesimal gravitational action2 we cannot1 therefore1 obtain any evidence of its existence except when it changes its state4 ,in fact1 our knowledge of atoms is like that which a ticket collector has of the population of his town3 he knows nothing of those who stay quietly at home4 ,now at some moment1 according to laws of which we have only statistical knowledge1 the electron in our atom jumps to a smaller orbit1 and the energy lost to the atom travels outward in a light-wave4 ,we know no causal law as to when the electron will jump1 though we know how far it will jump and exactly what will happen in the neighbourhood when it does4 ,at least1 when ,i say we know exactly what will happen1 ,i ought to say that we know exactly the mathematical laws of what will happen4 ,a series of events1 having quantitative characteristics which obey certain equations1 will travel outward in all directions from the electron1 and will proceed quite regularly1 like ripples on a pool1 until other matter is encountered4 ,we have here one important and apparently fundamental kind of causal law1 the kind regulating the propagation of light in vacuo4 ,this is summed up in ,maxwell's equations1 which enable us to calculate the diffusion of an electro-magnetic disturbance starting from a source4 ,so long as two such disturbances do not meet1 the matter is exceedingly simple2 but the equations also tell us what happens when they do meet4 ,we then have1 as always in traditional physics1 two separate tendencies1 which have a resultant compounded according to mathematical laws1 of which the parallelogram law is the oldest and simplest4 ,that is to say1 each previous circumstance in the space-time neighbourhood contributes a tendency1 and the resulting event is obtained by compounding these tendencies according to a mathematical law4 ,so far1 we have been considering only electro-magnetic phenomena in empty space4 ,we have another set of facts about empty space1 namely those upon which gravitation depends4 ,these have to do with the structure of space-time1 and show that this structure has singularities in the regions where there is matter1 which spread with diminishing intensity as we get away from these regions4 ,you may conceive the structure of space-time on the analogy of a pond with a fountain playing in it1 so that wherever a spray falls from the fountain there is a little hill of water which flattens quickly as you get away from the spot where the spray falls4 ,here again the same sort of thing applies3 to infer the structure in a small region of space-time from that in the neighbourhood1 it will be necessary to superpose a number of tendencies according to mathematical rules4 ,thus philosophically this introduces no novelty4 ,but now consider what happens when the wave of light which started from our hydrogen atom comes in contact with matter4 ,various things may happen4 ,the matter may absorb all or some of the energy of the light-ray2 this is the interesting case from our point of view4 ,the absorption may take the form of causing the electrons to move in larger orbits1 in which case1 later1 when they return to their previous orbits1 we get the phenomenon of fluorescence4 ,or the body may become heated2 or it may visibly move1 like a radiometer4 ,the effects upon bodies depend upon the bodies as well as the light4 ,some of them can be individually predicted1 others can only be calculated in statistical averages2 this depends upon whether quantum considerations come in or not4 ,where they do1 we can enumerate possibilities1 and state the relative frequencies with which they will be realised1 but we cannot tell which will be realised in any given case4 ,so far1 we have considered the radiation of energy from matter into empty space1 its propagation in empty space and its impact on matter from empty space4 ,we have not considered the history of a given piece of matter1 or the distinction between matter and empty space4 ,the essence of matter appears to be this3 ,we can distinguish series of events in space-time which have a certain kind of close resemblance to each other1 such that common sense regards them as manifestations of one 8thing04 ,but when we look closely at the question1 it turns out that what physics offers is something more abstract than this4 ,take1 e4 g4 the continued existence of a certain electron4 ,this means to say that events in a certain neighbourhood will be such as can be calculated on the assumption that there is an electric charge of a certain standard magnitude in the middle of that neighbourhood2 and that the neighbourhoods of which this is true form a tube in space-time4 ,so long as we stick to the standpoint of pure physics there is a certain air of taking in each other's washing about the whole business4 ,events in empty space are only known as regards their abstract mathematical characteristics2 matter is only an abstract mathematical characteristic of events in empty space4 ,this seems rather a cold world4 ,but as a matter of fact we know some things that are a little more concrete4 ,we know1 e4g4 what it feels like when we see things4 ,from the point of view of physics1 when our light-wave starts out through empty space1 if it presently reaches our eye we know one link in the causal chain1 namely the visual sensation1 otherwise than as a term in an abstract mathematical formula4 ,and it is this one term which forms the basis for our belief in all the rest4 ,seeing is believing4 ,at this point ,i propose to make a brief digression on the subject of our evidence for causal laws4 ,the laws for which we first get evidence are such as do not hold always1 but only as a general rule4 ,as a rule1 when you decide to move your arm1 it moves3 but sometimes it is paralysed and remains motionless4 ,as a rule1 when you say how-do-you-do to an old friend1 he says the same to you2 but he may have grown blind and deaf since you last saw him1 and not notice your words or gesture4 ,as a rule1 if you put a match to gunpowder1 it explodes2 but it may have got damp4 ,it is such common but not invariable rules of sequence that we notice first4 ,but science is always seeking to replace them by laws that may have no exceptions4 ,we notice first that heavy bodies fall1 then that some bodies do not fall4 ,then we generalise both sets of facts into the law of gravitation and the laws of resistance of the air4 ,these more general laws do not state that anything will actually happen3 they state a tendency1 and lead to the conclusion that what actually happens is the resultant of a number of tendencies4 ,we cannot know what the resultant will be unless we know a great deal about the neighbourhood concerned4 ,for example1 ,i might1 within the next few seconds be hit on the head by a meteorite2 to know whether this is going to happen1 ,i must know what matter is to be found in the neighbourhood of the earth4 ,this illustrates that actual predictions based upon laws which are perfectly valid may always be falsified by some unknown fact of what we may call geography4 ,moreover1 we can never be sure that our scientific laws are quite right2 of this the ,einsteinian modification of the law of gravitation has afforded a notable instance4 ,let us now return to the relation between perception and the causal laws of physics4 ,having realised the abstractness of what physics has to say1 we no longer have any difficulty in fitting the visual sensation into the causal series4 ,it used to be thought 8mysterious0 that purely physical phenomena should end in something mental4 ,that was because people thought they knew a lot about physical phenomena1 and were sure they differed in quality from mental phenomena4 ,we now realise that we know nothing of the intrinsic quality of physical phenomena except when they happen to be sensations1 and that therefore there is no reason to be surprised that some are sensations1 or to suppose that the others are totally unlike sensations4 ,the gap between mind and matter has been filled in1 partly by new views of mind1 but much more by the realisation that physics tells us nothing as to the intrinsic character of matter4 ,i conceive what happens when we see an object more or less on the following lines4 ,for the sake of simplicity1 let us take a small self-luminous object4 ,in this object1 a certain number of atoms are losing energy and radiating it according to the quantum principle4 ,the resulting light-waves become superposed according to the usual mathematical principles2 each part of each light-wave consists of events in a certain region of space-time4 ,on coming in contact with the human body1 the energy in the light-wave takes new forms1 but there is still causal continuity4 ,at last it reaches the brain1 and there one of its constituent events is what we call a visual sensation4 ,this visual sensation is popularly called seeing the object from which the light-waves started--or from which they were reflected if the object was not self-luminous4 ,thus what is called a perception is only connected with its object through the laws of physics4 ,its relation to the object is causal and mathematical2 we cannot say whether or not it resembles the object in any intrinsic respect1 except that both it and the object are brief events in space-time4 ,i think we may lay down the following universal characteristics of causal laws in an advanced science4 ,given any event1 there are other events at neighbouring places in space-time which will occur slightly later if no other factors intervene2 but in practice other factors almost always do intervene1 and1 in that case1 the event which actually occurs at any point of space-time is a mathematical resultant of those which would have followed the various neighbouring events if they had been alone concerned4 ,the equations of physics give the rules according to which events are connected1 but all are of the above sort4 ,formerly it was thought that the equations of physics sufficed1 theoretically1 to determine the course of affairs in the physical world1 given all the facts about some finite stretch of time1 however short4 ,now it appears that this is not the case1 so far as the known equations are concerned4 ,the known equations suffice to determine what happens in empty space1 and statistical averages as to what happens to matter2 but they do not tell us when an individual atom will absorb or radiate energy4 ,whether there are laws1 other than those of statistics1 governing the behaviour of an individual atom in this respect1 we do not know4 ,it should be observed that there are causal laws of a different sort from those of pure physics2 such are the laws that light-waves 8cause0 visual sensations and sound-waves 8cause0 auditory sensations4 ,all the empirical evidence for physics rests upon such laws1 therefore nothing in physics can have a higher degree of certainty than such laws have4 ,let us stop a moment to ask what we mean by 8cause0 in this connection4 ,the connection of light-waves and visual sensations looks a little different according as we start with physics or with psychology1 though1 of course1 ultimately the result must be the same4 ,let us first start with physics4 ,i say1 then1 that when a light-wave travels outwards from a body there are successive events at successive places1 and that the corresponding event in a brain behind a normal eye is a visual sensation4 ,this is the only event in the whole series about which ,i can say anything not purely abstract and mathematical4 ,now let us start from the sensation4 ,i say1 then1 that this sensation is one of a vast series of connected events1 travelling out from a centre according to certain mathematical laws1 in virtue of which the sensation enables me to know a good deal about events elsewhere4 ,that is why the sensation is a source of physical knowledge4 ,it will be seen that1 according to the view ,i have been advocating1 there is no difficulty about interaction between mind and body4 ,a sensation is merely one link in a chain of physical causation2 when we regard the sensation as the end of such a chain1 we have what would be regarded as an effect of matter on mind2 when as the beginning1 an effect of mind on matter4 ,but mind is merely a cross-section in a stream of physical causation1 and there is nothing odd about its being both an effect and a cause in the physical world4 ,thus physical causal laws are those that are fundamental4 ,there seems no reason to regard causation as a priori1 though this question is not simple4 ,given certain very general assumptions as to the structure of space-time1 there are bound to be what we have called causal laws4 ,these general assumptions must really replace causality as our basic principles4 ,but1 general as they are1 they cannot be taken as a priori2 they are the generalisation and abstract epitome of the fact that there are causal laws1 and this must remain merely an empirical fact1 which is rendered probable1 though not certain1 by inductive arguments4 ,,chapter ,,xv ,,the ,,nature ,,of ,,our ,,knowledge ,,of ,,physics ,in this chapter1 we shall seek an answer to two questions3 ,first1 how do we know about the world dealt with in physics8 ,secondly1 what do we know about it1 assuming the truth of modern physics8 ,first3 ,how do we know about the physical world8 ,we have already seen that this question cannot have a simple answer1 since the basis of inference is something that happens in our own heads1 and our knowledge of anything outside our own heads must be more or less precarious4 ,for the present1 ,i shall take it for granted that we may accept testimony1 with due precautions4 ,in other words1 ,i shall assume that what we hear when1 as we believe1 others are speaking to us1 does in fact have 8meaning0 to the speaker1 and not only to us2 with a corresponding assumption as regards writing4 ,this assumption will be examined at a later stage4 ,for the present1 ,i will merely emphasise that it is an assumption1 and that it may possibly be false1 since people seem to speak to us in dreams1 and yet1 on waking1 we become persuaded that we invented the dream4 ,it is impossible to prove1 by a demonstrative argument1 that we are not always dreaming2 the best we can hope is a proof that this is improbable4 ,but for the present let us leave this discussion on one side1 and assume that the words we hear and read 8mean0 what they would if we spoke or wrote them4 ,on this basis1 we have reason to know that the worlds of different people are alike in certain respects and different in certain others4 ,take1 for example1 the audience at a theatre3 they all1 we say1 hear the same words and see the same gestures1 which1 moreover1 are those that the actors wish them to hear and see4 ,but those who are near the stage hear the words more loudly than those further off2 they also hear them somewhat earlier4 ,and those who sit on the right do not see quite what is seen by those who sit on the left or in the centre4 ,these differences are of two sorts3 on the one hand1 some people can see something invisible to others2 on the other hand1 when two people1 as we say1 see the 8same0 thing1 they see it differently owing to effects of perspective and of the way the light is reflected4 ,all this is a question of physics1 not of psychology2 for if we place a camera in an empty seat in the theatre1 the perspective in the resultant photograph is intermediate between the perspectives that are seen by persons sitting on either side2 indeed the whole matter of perspective is determined by quite simple geometrical laws4 ,these laws show also what is common to the shapes that two people see when they see the 8same0 thing from different points of view3 what is common is what is studied by projective geometry1 which is concerned with what is independent of measurement in geometrical figures4 ,all the differences in appearance due to perspective have to be learned in learning to draw3 for this purpose1 it is necessary to learn to see things as they really seem1 and not as they seem to seem4 ,but1 it will be said1 what can you mean by how things 8really0 seem and how they 8seem0 to seem8 ,we come here upon an important fact about learning4 ,when1 in early infancy1 we are learning to correlate sight and touch1 we acquire the habit of reacting to a visual stimulus in a manner which is more 8objective0 than that in which a camera reacts4 ,when we see a coin not directly in front of us1 we judge it to be circular1 although the camera would show it as oval1 and a man would have to make it oval in a picture of a scene which contained it4 ,we learn1 therefore1 to react to a visual shape in a manner corresponding to how it would appear if it were in the centre of the field of vision1 provided we do not immediately focus upon it1 which is what we naturally do when anything visible interests us4 ,as a matter of fact1 we are constantly looking in different directions1 and1 as a rule1 only noticing what1 at the moment1 is in the centre of our field of vision4 ,thus our visual world consists rather of a synthesis of things viewed directly in succession than of things seen simultaneously while the centre of the field is kept fixed4 ,this is one reason why the rules of perspective have to be learned1 although a picture which ignores them makes an impression of being 8wrong04 ,another reason for the objectivity of the impressions we derive from sight is correlation with other senses1 especially touch4 ,through this correlation we soon get to 8know0 that a man twenty yards away is 8really0 just as big as a man one yard away4 ,when children are learning to draw1 they find it very difficult to make distant objects sufficiently small1 because they know they are not 8really0 small4 ,we soon learn to judge the distance of a visual object1 and to react to it according to the size that it would have if touched--or travelled over--in the case of very large objects such as mountains4 ,our sense of size is not derived from sight1 but from such sources as touch and locomotion2 our metrical judgments1 when the stimulus is only visual1 are a result of previous experience4 ,by the time a child can speak well1 he has had a great deal of this kind of experience4 ,consequently our verbal reactions contain a great deal more objectivity than they would if they came at an earlier stage of infancy4 ,the result is that a number of people can view a scene simultaneously1 and use exactly the same words about it4 ,the words which we naturally use in describing what we see are those describing features that will also be evident to others in our neighbourhood4 ,we say1 8there is a man01 not1 8there is a coloured shape whose visual dimensions are such-and-such an angle vertically1 and such another horizontally04 ,the inference is a physiological inference1 and only subsequent reflection makes us aware that it has taken place4 ,we can1 however1 become aware of it through occasional mistakes2 a dot on the window-pane may be mistaken for a man in a distant field4 ,in this case1 we can discover our error by opening the window1 or by moving the head4 ,in general1 however1 physiological inferences of this sort are correct1 since they have resulted from correlations which are very common1 and are likely to be present on a given occasion4 ,consequently our words tend to conceal what is private and peculiar in our impressions1 and to make us believe that different people live in a common world to a greater extent than is in fact the case4 ,we have been using the word 8objectivity0 in the preceding pages1 and it is time to consider exactly what we mean by it4 ,suppose some scene--say in a theatre--is simultaneously seen by a number of people and photographed by a number of cameras4 ,the impression made upon a person or a camera is in some respects like that made upon other persons and cameras1 in other respects different4 ,we shall call the elements which are alike 8objective0 elements in the impression1 and those which are peculiar we shall call 8subjective04 ,thus those features of shapes which are considered in projective geometry will be objective1 whereas those considered in metrical geometry 7where lengths and angles are measured7 cannot be made objective through sight alone1 but demand the use of other senses4 ,in the photographs1 a man on the stage will be longer if the camera is near the stage than if it is far off1 assuming all the cameras to be alike4 ,but if four actors are standing in a row in one photograph1 they will be standing in a row in another2 this is an 8objective0 feature of the impression4 ,and the differences in the visual impressions of a number of spectators with normal eyesight are exactly analogous to the differences in the photographs2 so also are the likenesses4 ,thus the 8subjectivity0 that we are speaking about at present is something belonging to the physical world1 not to psychology4 ,it marks the fact that the stimulus1 whether to an eye or to a camera1 is not exactly the same wherever the eye or the camera may be placed2 there are features of the stimulus which are constant 7within limits71 but there are others which are different from any two different points of view4 ,the tendency of our perceptions is to emphasise increasingly the objective elements in an impression1 unless we have some special reason1 as artists have1 for doing the opposite4 ,this tendency begins before speech1 is much accentuated after speech has been acquired1 and is prolonged by scientific physics4 ,the theory of relativity is only the last term1 so far1 in the elimination of subjective elements from impressions4 ,but it must not be supposed that the subjective elements are any less 8real0 than the objective elements2 they are only less important4 ,they are less important because they do not point to anything beyond themselves as the others do4 ,we want our senses to give us information1 i4e4 to tell us about something more than our own momentary impression4 ,we acquire information through our senses if we attend to the objective elements in the impression and ignore the others2 but the subjective elements are just as truly part of the actual impression4 ,this is obvious as soon as we realise that the camera is as subjective as we are4 ,such considerations lead irresistibly to the scientific view that1 when an object can be seen or photographed from a number of points of view1 there is a connected set of events 7light-waves7 travelling outward from a centre2 that1 moreover1 there are some respects in which all these events are alike1 and others in which they differ one from another4 ,we must not think of a light-wave as a 8thing01 but as a connected group of rhythmical events4 ,the mathematical characteristics of such a group can be inferred by physics1 within limits2 but the intrinsic character of the component events cannot be inferred4 ,the events constituting light-waves are only known through their effects upon our eyes1 optic nerves1 and brains1 and these effects are not themselves light-waves1 as is obvious from the fact that nerves and brains are not transparent4 ,light in the physical world1 therefore1 must consist of events which are in some way different from the events which happen when we see2 but we cannot say more than this as to the intrinsic quality of these external events4 ,moreover1 when a number of people1 as we say1 8see the same thing01 what we have reason to believe is that light-waves emanating from a certain region have reached the eyes of all these people4 ,as to what is in the region from which the light-waves come1 we cannot tell4 ,but--so the plain man is tempted to argue--we can tell quite well1 because we can touch objects that we see1 and discover that there is something hard and solid in the place from which the light-waves come4 ,or1 again1 we may find that there is something there which1 though not solid1 is very hot1 and burns us when we try to touch it4 ,we all feel that touch gives more evidence of 8reality0 than sight2 ghosts and rainbows can be seen but not touched4 ,one reason for this greater sense of reality is that our spatial relation to an object when we touch it with our finger-tips is given1 and therefore an object does not give such different impressions of touch to different people as it does of sight4 ,another reason is that there are a number of objects that can be seen but not touched--reflections1 smoke1 mist1 etc4--and that these objects are calculated to surprise the inexperienced4 ,none of these facts1 however1 justify the plain man in supposing that touch makes him know real things as they are1 though we are verbally forced to admit that it brings him into 8contact0 with them4 ,we have seen on an earlier occasion how complex is the physical and physiological process leading from the object to the brain when we touch something2 and we have seen that illusions of touch can be produced artificially4 ,what we experience when we have a sensation of touch is1 therefore1 no more a revelation of the real nature of the object touched than what we experience when we look at it4 ,as a matter of fact1 if modern physics is to be believed1 sight1 prudently employed1 gives us a more delicate knowledge concerning objects than touch can ever do4 ,touch1 as compared with sight1 is gross and massive4 ,we can photograph the path of an individual electron4 ,we perceive colours which indicate the changes happening in atoms4 ,we can see faint stars even though the energy of the light that reaches us from them is inconceivably minute4 ,sight may deceive the unwary more than touch1 but for accurate scientific knowledge it is incomparably superior to any of the other senses4 ,it is chiefly through ideas derived from sight that physicists have been led to the modern conception of the atom as a centre from which radiations travel4 ,we do not know what happens in the centre4 ,the idea that there is a little hard lump there1 which is the electron or proton1 is an illegitimate intrusion of common-sense notions derived from touch4 ,for aught we know1 the atom may consist entirely of the radiations which come out of it4 ,it is useless to argue that radiations cannot come out of nothing4 ,we know that they come1 and they do not become any more really intelligible by being supposed to come out of a little lump4 ,modern physics1 therefore1 reduces matter to a set of events which proceed outward from a centre4 ,if there is something further in the centre itself1 we cannot know about it1 and it is irrelevant to physics4 ,the events that take the place of matter in the old sense are inferred from their effect on eyes1 photographic plates1 and other instruments4 ,what we know about them is not their intrinsic character1 but their structure and their mathematical laws4 ,their structure is inferred chiefly through the maxim 8same cause1 same effect04 ,it follows from this maxim that if the effects are different1 the causes must be different2 if1 therefore1 we see red and blue side by side1 we are justified in inferring that in the direction where we see red something different is happening from what is happening in the direction where we see blue4 ,by extensions of this line of argument we arrive at the mathematical laws of the physical world4 ,physics is mathematical1 not because we know so much about the physical world1 but because we know so little3 it is only its mathematical properties that we can discover4 ,for the rest1 our knowledge is negative4 ,in places where there are no eyes or ears or brains there are no colours or sounds1 but there are events having certain characteristics which lead them to cause colours and sounds in places where there are eyes and ears and brains4 ,we cannot find out what the world looks like from a place where there is nobody1 because if we go to look there will be somebody there2 the attempt is as hopeless as trying to jump on one's own shadow4 ,matter as it appears to common sense1 and as it has until recently appeared in physics1 must be given up4 ,the old idea of matter was connected with the idea of 8substance01 and this1 in turn1 with a view of time that the theory of relativity shows to be untenable4 ,the old view was that there is one cosmic time1 and that1 given any two events in any two parts of the universe1 either they are simultaneous1 or the first is earlier than the second1 or the second earlier than the first4 ,it was thought that the time-order of the two events must always be objectively definite1 although we might be unable to determine it4 ,we now find that this is not the case4 ,events which can be regarded as all in one place1 or all parts of the history of one piece of matter1 still have a definite time-order4 ,so do events in different places if a person situated where the second takes place can see the first before the second happens1 or1 more exactly1 if light can travel from the place of the one to the place of the other so as to reach the other place before the second event4 7,here we mean by a 8place0 the position of a given piece of matter3 however the matter may move relatively to other matter1 it is always in the same 8place0 from its own point of view47 ,but if light travelling from the place of the one event to the place of the other event arrives at the place of the other event after the other event has taken place1 and conversely1 then there is no definite objective time-order of the two events1 and there is no reason for regarding either as earlier than the other2 nor yet for regarding the two as simultaneous2 ideally careful observers will judge differently according to the way in which they are moving4 ,thus time is not cosmic1 but is to some extent individual and personal for each piece of matter4 ,what do we mean by a 8piece of matter0 in this statement8 ,we do not mean something that preserves a simple identity throughout its history1 nor do we mean something hard and solid1 nor even a hypothetical thing-in-itself known only through its effects4 ,we mean the 8effects0 themselves1 only that we no longer invoke an unknowable cause for them4 ,we find that energy in various forms spreads outwards from various centres2 we find also that such centres have a certain degree of persistence1 though this persistence is not absolute--the modern physicist faces cheerfully the possibility that an electron and a proton may mutually annihilate each other1 and even suggests that this may be the main source of the radiant energy of the stars1 because when it happens it makes an explosion4 ,what is asserted may be put as follows3 ,when energy radiates from a centre1 we can describe the laws of its radiation conveniently by imagining something in the centre1 which we will call an electron or a proton according to circumstances1 and for certain purposes it is convenient to regard this centre as persisting1 i4e4 as not a single point in space-time but a series of such points1 separated from each other by time-like intervals4 ,all this1 however1 is only a convenient way of describing what happens elsewhere1 namely the radiation of energy away from the centre4 ,as to what goes on in the centre itself1 if anything1 physics is silent4 ,what ,dr4 ,whitehead calls the 8pushiness0 of matter disappears altogether on this view4 8,matter0 is a convenient formula for describing what happens where it isn't4 ,i am talking physics1 not metaphysics2 when we come to metaphysics1 we may be able1 tentatively1 to add something to this statement1 but science alone can hardly add to it4 ,materialism as a philosophy becomes hardly tenable in view of this evaporation of matter4 ,but those who would formerly have been materialists can still adopt a philosophy which comes to much the same thing in many respects4 ,they can say that the type of causation dealt with in physics is fundamental1 and that all events are subject to physical laws4 ,i do not wish1 as yet1 to consider how far such a view should be adopted2 ,i am only suggesting that it must replace materialism as a view to be seriously examined4 ,,part ,,iii ,,man ,,from ,,within ,,chapter ,,xvi ,,self-,,observation ,it will be remembered that throughout ,part ,i1 we agreed to consider only those facts about a man which can be discovered by external observation1 and we postponed the question whether this excluded any genuine knowledge or not4 ,the usual view is that we know many things which could not be known without self-observation1 but the behaviourist holds that this view is mistaken4 ,i might be inclined to agree wholly with the behaviourist but for the considerations which were forced upon us in ,part ,,ii1 when we were examining our knowledge of the physical world4 ,we were then led to the conclusion that1 assuming physics to be correct1 the data for our knowledge of physics are infected with subjectivity1 and it is impossible for two men to observe the same phenomenon except in a rough and approximate sense4 ,this undermines the supposed objectivity of the behaviourist method1 at least in principle2 as a matter of degree1 it may survive to some extent4 ,broadly speaking1 if physics is true and if we accept a behaviourist definition of knowledge such as that of ,chapter ,,viii1 we ought1 as a rule1 to know more about things that happen near the brain than about things that happen far from it1 and most of all about things that happen in the brain4 ,this seemed untrue because people thought that what happens in the brain is what the physiologist sees when he examines it2 but this1 according to the theory of ,chapter ,,xii1 happens in the brain of the physiologist4 ,thus the a priori objection to the view that we know best what happens in our brains is removed1 and we are led back to self-observation as the most reliable way of obtaining knowledge4 ,this is the thesis which is to be expanded and sustained in the present chapter4 ,as every one knows1 the certainty of self-observation was the basis of ,descartes' system1 with which modern philosophy began4 ,descartes1 being anxious to build his metaphysic only upon what was absolutely certain1 set to work1 as a preliminary1 to doubt anything that he could make himself doubt4 ,he succeeded in doubting the whole external world1 since there might be a malicious demon who took pleasure in presenting deceitful appearances to him4 7,for that matter1 dreams would have supplied a sufficient argument47 ,but he could not manage to doubt his own existence4 ,for1 said he1 ,i am really doubting2 whatever else may be doubtful1 the fact that ,i doubt is indubitable4 ,and ,i could not doubt if ,i did not exist4 ,he summed up the argument in his famous formula3 ,i think1 therefore ,i am4 ,and having arrived at this certainty1 he proceeded to build up the world again by successive inferences4 ,oddly enough1 it was very like the world in which he had believed before his excursion into scepticism4 ,it is instructive to contrast this argument with ,dr4 ,watson's4 ,dr4 ,watson1 like ,descartes1 is sceptical of many things which others accept without question2 and1 like ,descartes1 he believes that there are some things so certain that they can be safely used as the basis of a startling philosophy4 ,but the things which ,dr4 ,watson regards as certain are just those which ,descartes regarded as doubtful1 and the thing which ,dr4 ,watson most vehemently rejects is just what ,descartes regarded as absolutely unquestionable4 ,dr4 ,watson maintains that there is no such thing as thinking4 ,no doubt he believes in his own existence1 but not because he thinks he can think4 ,the things that strike him as absolutely indubitable are rats in mazes1 time-measurements1 physiological facts about glands and muscles1 and so on4 ,what are we to think when two able men hold such opposite views8 ,the natural inference would be that everything is doubtful4 ,this may be true1 but there are degrees of doubtfulness1 and we should like to know which of these two philosophers1 if either1 is right as to the region of minimum doubtfulness4 ,let us begin by examining ,descartes' view4 8,i think1 therefore ,i am0 is what he says1 but this won't do as it stands4 ,what1 from his own point of view1 he should profess to know is not 8,i think01 but 8there is thinking04 ,he finds doubt going on1 and says3 ,there is doubt4 ,doubt is a form of thought1 therefore there is thought4 ,to translate this into 8,i think0 is to assume a great deal that a previous exercise in scepticism ought to have taught ,descartes to call in question4 ,he would say that thoughts imply a thinker4 ,but why should they8 ,why should not a thinker be simply a certain series of thoughts1 connected with each other by causal laws8 ,descartes believed in 8substance01 both in the mental and in the material world4 ,he thought that there could not be motion unless something moved1 nor thinking unless some one thought4 ,no doubt most people would still hold this view2 but in fact it springs from a notion--usually unconscious--that the categories of grammar are also the categories of reality4 ,we have already seen that 8matter0 is merely a name for certain strings of sets of events4 ,it follows that what we call motion of matter really means that the centre of such a set of events at one time does not have the same spatial relations to other events as the connected centre at another time has to the connected other events4 ,it does not mean that there is a definite entity1 a piece of matter1 which is now in one place and now in another4 ,similarly1 when we say1 8,i think first this and then that01 we ought not to mean that there is a single entity 8,i0 which 8has0 two successive thoughts4 ,we ought to mean only that there are two successive thoughts which have causal relations of the kind that makes us call them parts of one biography1 in the same sort of way in which successive notes may be parts of one tune2 and that these thoughts are connected with the body which is speaking in the way 7to be further investigated7 in which thoughts and bodies are connected4 ,all this is rather complicated1 and cannot be admitted as part of any ultimate certainty4 ,what ,descartes really felt sure about was a certain occurrence1 which he described in the words 8,i think04 ,but the words were not quite an accurate representation of the occurrence2 indeed1 words never can escape from certain grammatical and social requirements which make them say at once more and less than we really mean4 ,i think we ought to admit that ,descartes was justified in feeling sure that there was a certain occurrence1 concerning which doubt was impossible2 but he was not justified in bringing in the word 8,i0 in describing this occurrence1 and it remains to be considered whether he was justified in using the word 8think04 ,in using a general word such as 8think01 we are obviously going beyond the datum1 from a logical point of view4 ,we are subsuming a particular occurrence under a heading1 and the heading is derived from past experience4 ,now all words are applicable to many occurrences2 therefore all words go beyond any possible datum4 ,in this sense1 it is impossible ever to convey in words the particularity of a concrete experience2 all words are more or less abstract4 ,such1 at least1 is a plausible line of argument1 but ,i am by no means sure that it is valid4 ,for example1 the sight of a particular dog may make the general word 8dog0 come into your mind2 you then know that it is a dog1 but you may not notice what sort of dog it is4 ,in this sense1 the knowledge with which we start is abstract and general2 that is to say1 it consists of a learned reaction to a stimulus of a certain sort4 ,the reactions1 at any rate in so far as they are verbal1 are more uniform than the stimuli4 ,a witness might be asked 8,did you see a dog80 8,yes40 8,what sort of dog80 8,oh1 just an ordinary dog2 ,i don't remember more about it40 ,that is to say1 the witness's reaction consisted of the generalised word 8dog0 and no more4 ,one is almost reminded of quantum phenomena in the atom4 ,when light falls on a hydrogen atom1 it may make the electron jump from the first orbit to the second1 or to the third1 etc4 ,each of these is a generalised reaction to a stimulus which has no corresponding generality4 ,so dogs and cats have each their individual peculiarities1 but the ordinary inobservant person responds with the generalised reaction 8dog0 or 8cat01 and the particularity of the stimulus leads to no corresponding particularity in the knowledge-reaction4 ,to return to ,descartes and his thinking3 it is possible1 according to what we have just said1 that ,descartes knew he was thinking with more certainty than he knew what he was thinking about4 ,this possibility requires that we should ask what he meant by 8thinking04 ,and since1 for him1 thinking was the primitive certainty1 we must not introduce any external stimulus1 since he considered it possible to doubt whether anything external existed4 ,descartes used the word 8thinking0 somewhat more widely than we should generally do nowadays4 ,he included all perception1 emotion1 and volition1 not only what are called 8intellectual0 processes4 ,we may perhaps with advantage concentrate upon perception4 ,descartes would say that1 when he 8sees the moon01 he is more certain of his visual percept than he is of the outside object4 ,as we have seen1 this attitude is rational from the standpoint of physics and physiology1 because a given occurrence in the brain is capable of having a variety of causes1 and where the cause is unusual common sense will be misled4 ,it would be theoretically possible to stimulate the optic nerve artificially in just the way in which light coming from the moon stimulates it2 in this case1 we should have the same experience as when we 8see the moon01 but should be deceived as to its external source4 ,descartes was influenced by an argument of this sort1 when he brought up the possibility of a deceitful demon4 ,therefore what he felt certain about was not what he had initially felt certain about1 but what remained certain after an argument as to the causes of perception4 ,this brings us to a distinction which is important1 but difficult to apply2 the distinction between what we in fact do not doubt1 and what we should not doubt if we were completely rational4 ,we do not in fact question the existence of the sun and moon1 though perhaps we might teach ourselves to do so by a long course of ,cartesian doubt4 ,even then1 according to ,descartes1 we could not doubt that we have the experiences which we have hitherto called 8seeing the sun0 and 8seeing the moon01 although we shall need different words if we are to describe these experiences correctly4 ,the question arises3 ,why should we not doubt everything8 ,why should we remain convinced that we have these experiences8 ,might not a deceitful demon perpetually supply us with false memories8 ,when we say 8a moment ago ,i had the experience which ,i have hitherto called seeing the sun01 perhaps we are deceived4 ,in dreams we often remember things that never happened4 ,at best1 therefore1 we can be sure of our present momentary experience1 not of anything that happened even half a minute ago4 ,and before we can so fix our momentary experience as to make it the basis of a philosophy1 it will be past1 and therefore uncertain4 ,when ,descartes said 8,i think01 he may have had certainty2 but by the time he said 8therefore ,i am01 he was relying upon memory1 and may have been deceived4 ,this line of argument leads to complete scepticism about everything4 ,if we are to avoid such a result1 we must have some new principle4 ,in actual fact1 we start by feeling certainty about all sorts of things1 and we surrender this feeling only where some definite argument has convinced us that it is liable to lead to error4 ,when we find any class of primitive certainties which never leads to error1 we retain our convictions in regard to this class4 ,that is to say1 wherever we feel initial certainty1 we require an argument to make us doubt1 not an argument to make us believe4 ,we may therefore take1 as the basis of our beliefs1 any class of primitive certainties which cannot be shown to lead us into error4 ,this is really what ,descartes does1 although he is not clear about it himself4 ,moreover1 when we have found an error in something of which we were previously certain1 we do not as a rule abandon entirely the belief which misled us1 but we seek1 if we can1 to modify it so that it shall no longer be demonstrably false4 ,this is what has happened with perception4 ,when we think we see an external object1 we may be deceived by a variety of causes4 ,there may be a mirage or a reflection2 in this case1 the source of the error is in the external world1 and a photographic plate would be equally deceived4 ,there may be a stimulus to the eye of the sort that makes us 8see stars01 or we may see little black dots owing to a disordered liver1 in which case1 the source of the error is in the body but not in the brain4 ,we may have dreams in which we seem to see all sorts of things2 in this case1 the source of the error is in the brain4 ,having gradually discovered these possibilities of error1 people have become somewhat wary as to the objective significance of their perceptions2 but they have remained convinced that they really have the perceptions they thought they had1 although the common-sense interpretation of them is sometimes at fault4 ,thus1 while retaining the conviction that they are sure of something1 they have gradually changed their view as to what it is that they are sure of4 ,nothing is known that tends to show error in the view that we really have the percepts we think we have1 so long as we are prudent in interpreting them as signs of something external4 ,that is the valid basis for ,descartes' view that 8thought0 is more certain than external objects4 ,when 8thought0 is taken to mean the experiences which we usually regard as percepts of objects1 there are sound reasons for accepting ,descartes' opinion to this extent4 ,let us now take up ,dr4 ,watson's view4 ,we shall find1 if ,i am not mistaken1 that his position also is to a very large extent valid4 ,that being so1 we shall seek to find an intermediate opinion1 accepting what seems valid and rejecting what seems doubtful in the contentions of both protagonists4 ,dr4 ,watson's view as to what is most certain is one which is in entire accordance with common sense4 ,all psychological matters the plain man regards as more or less open to question1 but he has no doubts about his office1 his morning train1 the tax-collector1 the weather1 and the other blessings of this life4 ,it may amuse him1 in an idle hour1 to listen to some one playing with the idea that life is a dream1 or suggesting that the thoughts of the people in the train are more real than the train4 ,but unless he is a philosophical lecturer1 he does not countenance such notions in business hours4 ,who can imagine a clerk in an office conceiving metaphysical doubts as to the existence of his boss8 ,or would any railroad president regard with favour the theory that his railroad is only an idea in the minds of the shareholders8 ,such a view1 he would say1 though it is often sound as regards gold-mines1 is simply silly when it comes to a railroad3 anybody can see it1 and can get himself run over if he wanders on the tracks under the impression that they do not exist4 ,belief in the unreality of matter is likely to lead to an untimely death1 and that1 perhaps1 is the reason why this belief is so rare1 since those who entertained it died out4 ,we cannot dismiss the common-sense outlook as simply silly1 since it succeeds in daily life2 if we are going to reject it in part1 we must be sure that we do so in favor of something equally tough as a means of coping with practical problems4 ,descartes says3 ,i think1 therefore ,i am4 ,watson says3 ,there are rats in mazes1 therefore ,i don't think4 ,at least1 a parodist might thus sum up his philosophy4 ,what ,watson really says is more like this3 7#a7 ,the most certain facts are those which are public1 and can be confirmed by the testimony of a number of observers4 ,such facts form the basis of the physical sciences3 physics1 chemistry1 biology1 anatomy1 physiology1 to mention only those that are relevant to the matter in question4 7#b7 ,the physical sciences are capable of affording an explanation of all the publicly observable facts about human behaviour4 7#c7 ,there is no reason to suppose that there are any facts about human beings that can be known only in some other way4 7#d7 ,in particular1 8introspection01 as a means of discovering by self-observation things that are in principle undiscoverable by observation of others1 is a pernicious superstition1 which must be swept away before any really sound knowledge of man becomes possible4 7#e7 ,and1 as a corollary1 there is no reason to believe in the existence of 8thought0 as opposed to speech and other bodily behaviour4 ,i have numbered the above propositions1 as it is important to keep them separate4 ,on the whole1 7#a71 7#b71 and 7#c7 seem to me to be true1 but 7#d7 and 7#e7 seem to me to be false4 ,behaviourists1 ,i think1 incline to the view that 7#d7 and 7#e7 follow from 7#a71 7#b71 and 7#c72 but this view ,i attribute to what ,i should regard as errors concerning the basis of physics4 ,that is why it was necessary to discuss physics before coming to a decision on this question of self-observation4 ,but let us examine each of the above propositions in turn4 7#a7 ,it is true that the facts upon which the physical sciences are based are all of them public1 in the sense that many men can observe them4 ,if a phenomenon is photographed1 any number of people can inspect the photograph4 ,if a measurement is made1 not only may several people be present1 but others can repeat the experiment4 ,if the result does not confirm the first observer1 the supposed fact is rejected4 ,the publicity of physical facts is always regarded as one of the greatest assets of physics4 ,on a common-sense basis1 therefore1 the first of the propositions in which we have summed up the behaviourist philosophy must be admitted4 ,there are1 however1 some very important provisos which must be mentioned4 ,in the first place1 a scientific observer is not expected to note his integral reaction to a situation1 but only that part of it which experience leads him to regard as 8objective01 i4e4 the same as the reaction of any other competent observer4 ,this process of learning to note only 8objective0 features in our reaction is1 as we have seen1 begun in infancy2 training in science only carries it further4 ,a 8good0 observer does not mention what is peculiar to himself in his reaction4 ,he does not say3 8,a boring speck of light danced about1 causing me eye-fatigue and irritation2 finally it settled at such-and-such a point40 ,he says simply3 8,the reading was such-and-such04 ,all this objectivity is a result of training and experience4 ,one may say1 in fact1 that very few men have the 8right0 reaction to a scientific situation4 ,therefore an immense amount of theory is mixed up with what passes in science as pure observation4 ,the nature and justification of this theory is a matter requiring investigation4 ,in the second place1 we must not misinterpret the nature of the publicity in the case of physical phenomena4 ,the publicity consists in the fact that a number of people make closely similar reactions at a given moment4 ,suppose1 for example1 that twelve men are told to watch a screen for the appearance of a bright light1 and to say 8now0 when it appears4 ,suppose the experimenter hears them all just when he himself sees the light2 then he has good reason to believe that they have each had a stimulus similar to his4 ,but physics compels us to hold that they have had twelve separate stimuli1 so that when we say they have all seen the same light we can only legitimately mean that their twelve stimuli had a common causal origin4 ,in attributing our perceptions to a normal causal origin outside ourselves1 we run a certain risk of error1 since the origin may be unusual3 there may be reflection or refraction on the way to the eye1 there may be an unusual condition of the eye or optic nerve or brain4 ,all these considerations give a certain very small probability that1 on a given occasion1 there is not such an outside cause as we suppose4 ,if1 however1 a number of people concur with us1 i4e4 simultaneously have reactions which they attribute to an outside cause that can be identified with the one we had inferred1 then the probability of error is enormously diminished4 ,this is exactly the usual case of concurrent testimony4 ,if twelve men1 each of whom lies every other time that he speaks1 independently testify that some event has occurred1 the odds in favour of their all speaking the truth are #djie to #a4 ,the same sort of argument shows that our public senses1 when confirmed by others1 are probably speaking the truth1 except where there are sources of collective illusion such as mirage or suggestion4 ,in this respect1 however1 there is no essential difference between matters of external observation and matters of self-observation4 ,suppose1 for example1 that1 for the first time in your life1 you smell assaftida4 ,you say to yourself 8that is a most unpleasant smell04 ,now unpleasantness is a matter of self-observation4 ,it may be correlated with physiological conditions which can be observed in others1 but it is certainly not identical with these1 since people knew that things were pleasant and unpleasant before they knew about the physiological conditions accompanying pleasure and its opposite4 ,therefore when you say 8that smell is unpleasant0 you are noticing something that does not come into the world of physics as ordinarily understood4 ,you are1 however1 a reader of psycho-analysis1 and you have learned that sometimes hate is concealed love and love is concealed hate4 ,you say to yourself1 therefore3 8,perhaps ,i really like the smell of assaftida1 but am ashamed of liking it04 ,you therefore make your friends smell it1 with the result that you soon have no friends4 ,you then try children1 and finally chimpanzees4 ,friends and children give verbal expression to their disgust3 chimpanzees are expressive1 though not verbal4 ,all these facts lead you to state3 8,the smell of assaftida is unpleasant04 ,although self-observation is involved1 the result has the same kind of certainty1 and the same kind of objective verification1 as if it were one of the facts that form the empirical basis of physics4 7#b7 ,the second proposition1 to the effect that the physical sciences are capable of affording an explanation of all the publicly observable facts about human behaviour1 is one as to which it is possible to argue endlessly4 ,the plain fact is that we do not yet know whether it is true or false4 ,there is much to be said in its favour on general scientific grounds1 particularly if it is put forward1 not as a dogma1 but as a methodological precept1 a recommendation to scientific investigators as to the direction in which they are to seek for solution of their problems4 ,but so long as much of human behaviour remains unexplained in terms of physical laws1 we cannot assert dogmatically that there is no residue which is theoretically inexplicable by this method4 ,we may say that the trend of science1 so far1 seems to render such a view improbable1 but to say even so much is perhaps rash1 though1 for my part1 ,i should regard it as still more rash to say that there certainly is such a residue4 ,i propose1 therefore1 as a matter of argument1 to admit the behaviourist position on this point1 since my objections to behaviourism as an ultimate philosophy come from quite a different kind of considerations4 7#c7 ,the proposition we are now to examine may be stated as follows3 8,all facts that can be known about human beings are known by the same method by which the facts of physics are known40 ,this ,i hold to be true1 but for a reason exactly opposite to that which influences the behaviourist4 ,i hold that the facts of physics1 like those of psychology1 are obtained by what is really self-observation1 although common sense mistakenly supposes that it is observation of external objects4 ,as we saw in ,chapter ,,xiii1 your visual1 auditory1 and other percepts are all in your head1 from the standpoint of physics4 ,therefore1 when you 8see the sun01 it is1 strictly speaking1 an event in yourself that you are knowing3 the inference to an external cause is more or less precarious1 and is on occasion mistaken4 ,to revert to the assaftida3 it is by a number of self-observations that you know that the smell of assaftida is unpleasant1 and it is by a number of self-observations that you know that the sun is bright and warm4 ,there is no essential difference between the two cases4 ,one may say that the data of psychology are those private facts which are not very directly linked with facts outside the body1 while the data of physics are those private facts which have a very direct causal connection with facts outside the body4 ,thus physics and psychology have the same method2 but this is rather what is commonly taken to be the special method of psychology than what is regarded as the method of physics4 ,we differ from the behaviourist in assimilating physical to psychological method1 rather than the opposite4 7#d7 ,is there a source of knowledge such as is believed in by those who appeal to 8introspection08 ,according to what we have just been saying1 all knowledge rests upon something which might1 in a sense1 be called 8introspection04 ,nevertheless1 there may be some distinction to be discovered4 ,i think myself that the only distinction of importance is in the degree of correlation with events outside the body of the observer4 ,suppose1 for example1 that a behaviourist is watching a rat in a maze1 and that a friend is standing by4 ,he says to the friend 8,do you see that rat80 ,if the friend says yes1 the behaviourist is engaged in his normal occupation of observing physical occurrences4 ,but if the friend says no1 the behaviourist exclaims1 8,i must give up this boot-legged whiskey04 ,in that case1 if his horror still permits him to think clearly1 he will be obliged to say that in watching the imaginary rat he was engaged in introspection4 ,there was certainly something happening1 and he could still obtain knowledge by observing what was happening1 provided he abstained from supposing that it had a cause outside his body4 ,but he cannot1 without outside testimony or some other extraneous information1 distinguish between the 8real0 rat and the 8imaginary0 one4 ,thus in the case of the 8real0 rat also1 his primary datum ought to be considered introspective1 in spite of the fact that it does not seem so2 for the datum in the case of the 8imaginary0 rat also does not seem to be merely introspective4 ,the real point seems to be this3 some events have effects which radiate all round them1 and can therefore produce reactions in a number of observers2 of these1 ordinary speech is an illustration4 ,but other events produce effects which travel linearly1 not spherically2 of these1 speech into a telephone from a sound-proof telephone box may serve as an illustration4 ,this can be heard by only one person beside the speaker2 if instead of a speaker we had an instrument at the mouthpiece1 only one person could hear the sound1 namely the person at the other end of the telephone4 ,events which happen inside a human body are like the noise in the telephone3 they have effects1 in the main1 which travel along nerves to the brain1 instead of spreading out in all directions equally4 ,consequently1 a man can know a great deal about his own body which another man can only know indirectly4 ,another man can see the hole in my tooth1 but he cannot feel my toothache4 ,if he infers that ,i feel toothache1 he still does not have the very same knowledge that ,i have2 he may use the same words1 but the stimulus to his use of them is different from the stimulus to mine1 and ,i can be acutely aware of the pain which is the stimulus to my words4 ,in all these ways a man has knowledge concerning his own body which is obtained differently from the way in which he obtains knowledge of other bodies4 ,this peculiar knowledge is1 in one sense1 8introspective01 though not quite in the sense that ,dr4 ,watson denies4 7#e7 ,we come now to the real crux of the whole matter1 namely to the question3 ,do we think8 ,this question is very ambiguous1 so long as 8thinking0 has not been clearly defined4 ,perhaps we may state the matter thus3 ,do we know events in us which would not be included in an absolutely complete knowledge of physics8 ,i mean by a complete knowledge of physics a knowledge not only of physical laws1 but also of what we may call geography1 i4e4 the distribution of energy throughout space-time4 ,if the question is put in this way1 ,i think it is quite clear that we do know things not included in physics4 ,a blind man could know the whole of physics1 but he could not know what things look like to people who can see1 nor what is the difference between red and blue as seen4 ,he could know all about wave-lengths1 but people knew the difference between red and blue as seen before they knew anything about wave-lengths4 ,the person who knows physics and can see knows that a certain wave-length will give him a sensation of red1 but this knowledge is not part of physics4 ,again1 we know what we mean by 8pleasant0 and 8unpleasant01 and we do not know this any better when we have discovered that pleasant things have one kind of physiological effect and unpleasant things have another4 ,if we did not already know what things are pleasant and what unpleasant1 we could never have discovered this correlation4 ,but the knowledge that certain things are pleasant and certain others unpleasant is no part of physics4 ,finally1 we come to imaginations1 hallucinations1 and dreams4 ,in all these cases1 we may suppose that there is an external stimulus1 but the cerebral part of the causal chain is unusual1 so that there is not in the outside world something connected with what we are imagining in the same way as in normal perception4 ,yet in such cases we can quite clearly know what is happening to us2 we can1 for example1 often remember our dreams4 ,i think dreams must count as 8thought01 in the sense that they lie outside physics4 ,they may be accompanied by movements1 but knowledge of them is not knowledge of these movements4 ,indeed all knowledge as to movements of matter is inferential1 and the knowledge which a scientific man should take as constituting his primary data is more like our knowledge of dreams than like our knowledge of the movements of rats or heavenly bodies4 ,to this extent1 ,i should say1 ,descartes is in the right as against ,watson4 ,watson's position seems to rest upon naive realism as regards the physical world1 but naive realism is destroyed by what physics itself has to say concerning physical causation and the antecedents of our perceptions4 ,on these grounds1 ,i hold that self-observation can and does give us knowledge which is not part of physics1 and that there is no reason to deny the reality of 8thought04 ,,chapter ,,xvii ,,images ,in this chapter we shall consider the question of images4 ,as the reader doubtless knows1 one of the battle-cries of behaviourism is 8death to images04 ,we cannot discuss this question without a good deal of previous clearing of the ground4 ,what are 8images0 as conceived by their supporters8 ,let us take this question first in the sense of trying to know some of the phenomena intended1 and only afterwards in the sense of seeking a formal definition4 ,in the ordinary sense1 we have visual images if we shut our eyes and call up pictures of scenery or faces we have known2 we have auditory images when we recall a tune without actually humming it2 we have tactual images when we look at a nice piece of fur and think how pleasant it would be to stroke it4 ,we may ignore other kinds of images1 and concentrate upon these1 visual1 auditory1 and tactual4 ,there is no doubt that we have such experiences as ,i have suggested by the above words2 the only question is as to how these experiences ought to be described4 ,then we have another set of experiences1 namely dreams1 which feel like sensations at the moment1 but do not have the same kind of relation to the external world as sensations have4 ,dreams1 also1 indubitably occur1 and again it is a question of analysis whether we are to say that they contain 8images0 or not4 ,the behaviourist does not admit images1 but he equally does not admit sensations and perceptions4 ,although he does not say so quite definitely1 he may be taken to maintain that there is nothing but matter in motion4 ,we cannot1 therefore1 tackle the question of images by contrasting them with sensations or perceptions1 unless we have first clearly proved the existence of these latter and defined their characteristics4 ,now it will be remembered that in ,chapter ,v we attempted a behaviourist definition of perception1 and decided that its most essential feature was 8sensitivity04 ,that is to say1 if a person always has a reaction of a certain kind ,b when he has a certain spatial relation to an object of a certain kind ,a1 but not otherwise1 then we say that the person is 8sensitive0 to ,a4 ,in order to obtain from this a definition of 8perception01 it is necessary to take account of the law of association2 but for the moment we will ignore this complication1 and say that a person 8perceives0 any feature of his environment1 or of his own body1 to which he is sensitive4 ,now1 however1 as a result of the discussion in ,chapter ,,xvi1 we can include in his reaction1 not only what others can observe1 but also what he alone can observe4 ,this enlarges the known sphere of perception1 practically if not theoretically4 ,but it leaves unchanged the fact that the essence of perception is a causal relation to a feature of the environment which1 except in astronomy1 is approximately contemporaneous with the perception1 though always at least slightly earlier1 owing to the time taken by light and sound to travel and the interval occupied in transmitting a current along the nerves4 ,let us now contrast with this what happens when you sit still with your eyes shut1 calling up pictures of places you have seen abroad1 and perhaps ultimately falling asleep4 ,dr4 ,watson1 if ,i understand him aright1 maintains that either there is actual stimulation of the retina1 or your pictures are mere word-pictures1 the words being represented by small actual movements such as would1 if magnified and prolonged1 lead to actual pronunciation of the words4 ,now if you are in the dark with your eyes shut1 there is no stimulation of the retina from without4 ,it may be that1 by association1 the eye can be affected through stimuli to other senses2 we have already had an example in the fact that the pupil can be taught to contract at a loud noise if this had been frequently experienced along with a bright light4 ,we cannot1 therefore1 dismiss the idea that a stimulus to one sense may1 as a result of past events1 have an effect upon the organs of another sense4 8,images0 might be definable as effects produced in this way4 ,it may be that1 when you see a picture of ,napoleon1 there is an effect upon your aural nerves analogous to that of having the word 8,napoleon0 pronounced in your presence1 and that that is why1 when you see the picture1 the word 8,napoleon0 comes into your head4 ,and similarly1 when you shut your eyes and call up pictures of foreign scenes1 you may actually pronounce1 completely or incipiently1 the word 8,italy01 and this may1 through association1 stimulate the optic nerve in a way more or less similar to that in which some actual place in ,italy stimulated it on some former occasion4 ,thence association alone may carry you along through a series of journeys1 until at last1 when you fall asleep1 you think you are actually making them at the moment4 ,all this is quite possible1 but so far as ,i know there is no reason to hold that it is more than possible1 apart from an a priori theory excluding every other explanation4 ,what ,i think is clearly untenable is the view1 sometimes urged by ,dr4 ,watson1 that when we are1 as we think1 seeing imaginary pictures with the eyes shut1 we are really only using such words as would describe them4 ,it seems to me as certain as anything can be that1 when ,i visualise1 something is happening which is connected with the sense of sight4 ,for example1 ,i can call up quite clear mental pictures of the house in which ,i lived as a child2 if ,i am asked a question as to the furniture of any of the rooms in that house1 ,i can answer it by first calling up an image and then looking to see what the answer is1 just as ,i should look to see in an actual room4 ,it is quite clear to me that the picture comes first and that words after2 moreover1 the words need not come at all4 ,i cannot tell what is happening in my retina or optic nerve at these moments of visualisation1 but ,i am quite sure that something is happening which has a connection with the sense of sight that it does not have with other senses4 ,and ,i can say the same of aural and tactual images4 ,if this belief were inconsistent with anything else that seems to me equally certain1 ,i might be induced to abandon it4 ,but so far as ,i can see1 there is no such inconsistency4 ,it will be remembered that we decided in favour of perceptions as events distinct from those which they perceive1 and only causally connected with them4 ,there is1 therefore1 no reason why association should not work in this region as well as in the region of muscles and glands2 in other words1 there is no reason to deny what used to be called 8association of ideas01 in spite of the fact that bodily changes can also be associated4 ,if a physical basis is wanted1 it can be assumed to exist in the brain4 ,the state of the brain which causes us to hear the word 8,napoleon0 may become associated with the state of brain which causes us to see a picture of ,napoleon1 and thus the word and the picture will call each other up4 ,the association may be in the sense-organs or nerves1 but may equally well be in the brain4 ,so far as ,i know1 there is no conclusive evidence either way1 nor even that the association is not purely 8mental40 ,when we try to find a definition of the difference between a sensation and an image1 it is natural to look first for intrinsic differences4 ,but intrinsic differences between ordinary sensations and ordinary images1 for example as to 8liveliness01 are found to be subject to exceptions1 and therefore unsuitable for purposes of definition4 ,thus we are brought to differences as to causes and effects4 ,it is obvious that1 in an ordinary case1 you perceive a table because 7in some sense7 the table is there4 ,that is to say1 there is a causal chain leading backwards from your perception to something outside your body4 ,this alone1 however1 is hardly sufficient as a criterion4 ,suppose you smell peat smoke and think of ,ireland1 your thought can equally be traced to a cause outside your body4 ,the only real difference is that the outside cause 7peat smoke7 would not have had the effect 7images of ,ireland7 upon every normal person1 but only upon such as had smelt peat smoke in ,ireland1 and not all of them4 ,that is to say1 the normal cerebral apparatus does not cause the given stimulus to produce the given effect except where certain previous experiences have occurred4 ,this is a very vital distinction4 ,part of what occurs in us under the influence of a stimulus from without depends upon past experience2 part does not4 ,the former part includes images1 the latter consists of pure sensations4 ,this1 however1 as we shall see later1 is inadequate as a definition4 ,mental occurrences which depend upon past experience are called 8mnemic0 occurrences1 following ,semon4 ,images are thus to be included among mnemic occurrences1 at least so far as human experience goes4 ,this1 however1 does not suffice to define them1 since there are others1 e4g4 recollections4 ,what further defines them is their similarity to sensations4 ,this only applies strictly to simple images2 complex ones may occur without a prototype1 though all their parts will have prototypes among sensations4 ,such1 at least1 is ,hume's principle1 and on the whole it seems to be true4 ,it must not1 however1 be pressed beyond a point4 ,as a rule1 an image is more or less vague1 and has a number of similar sensations as its prototypes4 ,this does not prevent the connection with sensation in general1 but makes it a connection with a number of sensations1 not with one only4 ,it happens that1 when a complex of sensations has occurred at some time in a person's experience1 the recurrence of part of the whole tends to produce images of the remaining parts or some of them4 ,this is association1 and has much to do with memory4 ,it is common to speak of images as 8centrally excited01 as opposed to sensations1 which are excited by a stimulus to some sense organ4 ,in essence this is quite correct1 but there is need of some caution in interpreting the phrase4 ,sensations also have proximate causes in the brain2 images also may be due to some excitement of a sense-organ1 when they are roused by a sensation through association4 ,but in such cases there is nothing to explain their occurrence except the past experience and its effect on the brain4 ,they will not be aroused by the same stimulus in a person with similar sense-organs but different past experience4 ,the connection with past experience is clearly known2 it is1 however1 an explanatory hypothesis1 not directly verifiable in the present state of knowledge1 to suppose that this connection works through an effect of the past experience on the brain4 ,this hypothesis must be regarded as doubtful1 but it will save circumlocution to adopt it4 ,i shall therefore not repeat1 on each occasion1 that we cannot feel sure it is true4 ,in general1 where the causal connection with past experience is obvious1 we call an occurrence 8mnemic01 without implying this or that hypothesis as to the explanation of mnemic phenomena4 ,it is perhaps worth while to ask how we know that images are like the sensations which are their prototypes4 ,the difficulty of this question arises as follows4 ,suppose you call up an image of the ,brooklyn ,bridge1 and you are convinced that it is like what you see when you look at ,brooklyn ,bridge4 ,it would seem natural to say that you know the likeness because you remember ,brooklyn ,bridge4 ,but remembering is often held to involve1 as an essential element1 the occurrence of an image which is regarded as referring to a prototype4 ,unless you can remember without images1 it is difficult to see how you can be sure that images resemble prototypes4 ,i think that in fact you cannot be sure1 unless you can find some indirect means of comparison4 ,you might1 for example1 have photographs of ,brooklyn ,bridge taken from a given place on two different days1 and find them indistinguishable1 showing that ,brooklyn ,bridge has not changed in the interval4 ,you might see ,brooklyn ,bridge on the first of these days1 remember it on the second1 and immediately afterwards look at it4 ,in looking at it1 you might find every detail coming to you with a feeling of expectedness1 or you might find some details coming with a feeling of surprise4 ,in this case you would say that your image had been wrong as regards the details which were surprising4 ,or1 again1 you might make a picture of ,brooklyn ,bridge on paper1 from memory1 and then compare it with the original or a photograph4 ,or you might content yourself by writing down a description of it in words1 and verifying its accuracy by direct observation4 ,innumerable methods of this kind can be devised by which you can test the likeness of an image to its prototype4 ,the result is that there is often a great likeness1 though seldom complete accuracy4 ,the belief in the likeness of an image to its prototype is1 of course1 not generated in this way1 but only tested4 ,the belief exists prior to evidence as to its correctness1 like most of our beliefs4 ,i shall have more to say on this subject in the next chapter1 which will be concerned with memory4 ,but ,i think enough has been said to show that it is not unreasonable to regard images as having a greater or less degree of resemblance to their prototypes4 ,to claim more is hardly justifiable4 ,we can now reach a definite conclusion about perception1 sensation1 and images4 ,let us imagine a number of people placed1 as far as possible1 in the same environment2 we will suppose that they sit successively in a certain chair in a dark room1 in full view of illuminated pictures of two eminent politicians of opposite parties whose names are written underneath them4 ,we will suppose that all of them have normal eyesight4 ,their reactions will be partly similar1 partly different4 ,if any of these observers are babies too young to have learnt to focus1 they will not see sharp outlines1 but a mere blurr1 not from an optical defect1 but from a lack of cerebral control over muscles4 ,in this respect1 experience has an effect even upon what must count as pure sensation4 ,but this difference is really analogous to the difference between having one's eyes open and having them shut2 the difference is in the sense-organ1 although it may be due to a difference in the brain4 ,we will therefore assume that all the spectators know how to adjust the eyes so as to see as well as possible1 and all try to see4 ,we shall then say that1 if the spectators differ as widely as is possible for normal human beings1 what is common to the reactions of all of them is sensation1 provided it is connected with the sense of sight1 or1 more correctly1 provided it has that quality which we observe to be common and peculiar to visual objects4 ,but probably all of them1 if they are over three months old1 will have tactile images while they see the pictures4 ,and if they are more than about a year old1 they will interpret them as pictures1 which represent three-dimensional objects2 before that age1 they may see them as coloured patterns1 not as representations of faces4 ,most animals1 though not all1 are incapable of interpreting pictures as representations4 ,but in an adult human being this interpretation is not deliberate2 it has become automatic4 ,it is1 ,i think1 mainly a question of tactile images3 the images you have in looking at a picture are not those appropriate to a smooth flat surface1 but those appropriate to the object represented4 ,if the object represented is a large one1 there will also be images of movement--walking round the object1 or climbing up it1 or what not4 ,all these are obviously a product of experience1 and therefore do not count as part of the sensation4 ,this influence of experience is still more obvious when it comes to reading the names of the politicians1 considering whether they are good likenesses1 and feeling what a fine fellow one of them looks and what unmitigated villainy is stamped upon the features of the other4 ,none of this counts as sensation1 yet it is part of a man's spontaneous reaction to an outside stimulus4 ,it is evidently difficult to avoid a certain artificiality in distinguishing between the effects of experience and the rest in a man's reaction to a stimulus4 ,perhaps we could tackle the matter in a slightly different way4 ,we can distinguish stimuli of different sorts3 to the eye1 the ear1 the nose1 the palate1 etc4 ,we can also distinguish elements of different sorts in the reaction3 visual elements1 auditory elements1 etc4 ,the latter are defined1 not by the stimulus1 but by their intrinsic quality4 ,a visual sensation and a visual image have a common quality which neither shares with an auditory sensation or an auditory image4 ,we may then say3 a visual image is an occurrence having the visual quality but not due to a stimulus to the eye1 i4e4 not having as a direct causal antecedent the incidence of light-waves upon the retina4 ,similarly an auditory image will be an occurrence having the auditory quality but not due to sound-waves reaching the ear1 and so on for the other senses4 ,this means a complete abandonment of the attempt to distinguish psychologically between sensations and images2 the distinction becomes solely one as to physical antecedents4 ,it is true that we can and do arrive at the distinction without scientific physics1 because we find that certain elements in our integral reactions have the correlations that make us regard them as corresponding to something external while others do not--correlations both with the experience of others and with our own past and future experiences4 ,but when we refine upon this common-sense distinction and try to make it precise1 it becomes the distinction in terms of physics as stated just now4 ,we might therefore conclude that an image is an occurrence having the quality associated with stimulation by some sense-organ1 but not due to such stimulation4 ,in human beings1 images seem to depend upon past experience1 but perhaps in more instinctive animals they are partly due to innate cerebral mechanisms4 ,in any case dependence upon experience is not the mark by which they are to be defined4 ,this shows how intimate is the dependence of traditional psychology upon physics1 and how difficult it is to make psychology into an autonomous science4 ,there is1 however1 still a further refinement necessary4 ,whatever is included under our present definition is an image1 but some things not included are also images4 ,the sight of an object may bring with it a visual image of some other object frequently associated with it4 ,this latter is called an image1 not a sensation1 because1 though also visual1 it is not appropriate to the stimulus in a certain sense3 it would not appear in a photograph of the scene1 or in a photograph of the retina4 ,thus we are forced to say3 the sensation element in the reaction to a stimulus is that part which enables you to draw inferences as to the nature of the extra-cerebral event 7if any7 which was the stimulus2#i the rest is images4 ,fortunately1 images and sensations usually differ in intrinsic quality2 this makes it possible to get an approximate idea of the external world by using the usual intrinsic differences1 and to correct it afterwards by means of the strict causal definition4 ,but evidently the matter is difficult and complicated1 depending upon physics and physiology1 not upon pure psychology4 ,this is the main thing to be realised about images4 #i ,i4e4 the immediate stimulus1 not the 8physical object04 ,the above discussion has suggested a definition of the word 8image04 ,we might have called an event an 8image0 when it is recognisably of the same kind as a 8percept01 but does not have the stimulus which it would have if it were a percept4 ,but if this definition is to be made satisfactory1 it will be necessary to substitute a different word in place of 8percept04 ,for example1 in the percept of a visible object it would be usual to include certain associated tactual elements1 but these must1 from our point of view1 count as images4 ,it will be better to say1 therefore1 that an 8image0 is an occurrence recognisably visual 7or auditory1 etc41 as the case may be71 but not caused by a stimulus which is of the nature of light 7or sound etc41 as the case may be71 or at any rate only indirectly so caused as a result of association4 ,with this definition1 ,i do not myself feel any doubt as to the existence of images4 ,it is clear that they constitute most of the material of dreams and day-dreams1 that they are utilised by composers in making music1 that we employ them when we get out of a familiar room in the dark 7though here the rats in mazes make a different explanation possible71 and that they account for the shock of surprise we have when we take salt thinking it is sugar or 7as happened to me recently7 vinegar thinking it is coffee4 ,the question of the causation of images--i4e4 whether it is in the brain or in other parts of the body--is not one which it is necessary to our purposes to decide1 which is fortunate1 since1 so far as ,i know1 there is not at present any adequate evidence on the point4 ,but the existence of images and their resemblance to perception is important1 as we shall see in the next chapter4 ,images come in various ways1 and play various parts4 ,there are those that come as accretions to a case of sensation1 which are not recognised as images except by the psychologist2 these form1 for example1 the tactual quality of things we only see1 and the visual quality of things we only touch4 ,i think dreams belong1 in part1 to this class of images3 some dreams result from misinterpreting some ordinary stimulus1 and in these cases the images are those suggested by a sensation1 but suggested more uncritically than if we were awake4 ,then there are images which are not attached to a present reality1 but to one which we locate in the past2 these are present in memory1 not necessarily always1 but sometimes4 ,then there are images not attached to reality at all so far as our feeling about them goes3 images which merely float into our heads in reverie or in passionate desire4 ,and finally there are images which are called up voluntarily1 for example1 in considering how to decorate a room4 ,this last kind has its importance1 but ,i shall say nothing more about it at present1 since we cannot profitably discuss it until we have decided what we are to mean by the word 8voluntary04 ,the first kind1 which comes as an accretion to sensation1 and gives to our feeling of objects a certain rotundity and full-bloodedness which the stimulus alone would hardly warrant1 has been considered already4 ,therefore what remains for the present is the use of images in memory and imagination2 and of these two ,i shall begin with memory4 ,,chapter ,,xviii ,,imagination ,,and ,,memory ,in this chapter we have to consider the two topics of imagination and memory4 ,the latter has already been considered in ,chapter ,,vi1 but there we viewed it from outside4 ,we want now to ask ourselves whether there is anything further to be known about it by taking account of what is only perceptible to the person remembering4 ,as regards the part played by images1 ,i do not think this is essential4 ,sometimes there are memory-images1 sometimes not2 sometimes when images come in connection with memory1 we may nevertheless know that the images are incorrect1 showing that we have also some other and more reliable source of memory4 ,memory may depend upon images1 as in the case mentioned above1 of the house where ,i lived as a child4 ,but it may also be purely verbal4 ,i am a poor visualiser1 except for things ,i saw before ,i was ten years old2 when now ,i meet a man and wish to remember his appearance1 ,i find that the only way is to describe him in words while ,i am seeing him1 and then remember the words4 ,i say to myself3 8,this man has blue eyes and a brown beard and a small nose2 he is short1 with a rounded back and sloping shoulders04 ,i can remember these words for months1 and recognise the man by means of them1 unless two men having these characteristics are present at once4 ,in this respect1 a visualiser would have the advantage of me4 ,nevertheless1 if ,i had made my verbal inventory sufficiently extensive and precise1 it would have been pretty sure to answer its purpose4 ,i do not think there is anything in memory that absolutely demands images as opposed to words4 ,whether the words we use in 8thought0 are themselves sometimes images of words1 or are always incipient movements 7as ,watson contends71 is a further question1 as to which ,i offer no opinion1 since it ought to be capable of being decided experimentally4 ,the most important point about memory is one which has nothing to do with images1 and is not mentioned in ,watson's brief discussion4 ,i mean the reference to the past4 ,this reference to the past is not involved in mere habit memory1 e4g4 in skating or in repeating a poem formerly learned4 ,but it is involved in recollection of a past incident4 ,we do not1 in this case1 merely repeat what we did before3 then1 we felt the incident as present1 but now we feel it as past4 ,this is shown in the use of the past tense4 ,we say to ourselves at the time 8,i am having a good dinner01 but next day we say 8,i did have a good dinner04 ,thus we do not1 like a rat in a maze1 repeat our previous performance3 we alter the verbal formula4 ,why do we do so8 ,what constitutes this reference of a recollection to the past8#aj #aj ,on this subject1 cf4 ,broad1 ,the ,mind and ,its ,place in ,nature1 p4 #bfd ff41 in his chapter on 8,memory04 ,let us take up the question first from the point of view of sensitivity4 ,the stimulus to a recollection is1 no doubt1 always something in the present1 but our reaction 7or part of it7 is more intimately related to a certain past event than to the present stimulus4 ,this1 in itself1 can be paralleled in inanimate objects1 for example1 in a gramophone record4 ,it is not the likeness of our reaction to that called forth on a former occasion that concerns us at the moment2 it is its un-likeness1 in the fact that now we have the feeling of pastness1 which we did not have originally4 ,you cannot sing into a dictaphone 8,i love you01 and have it say five days hence 8,i loved you last ,wednesday02 yet that is what we do when we remember4 ,i think1 however1 that this feature of memory is probably connected with a feature of reactions due to association when the association is cerebral3 ,i think also that this is connected with the difference in quality that exists usually1 though not always1 between images and sensations4 ,it would seem that1 in such cases1 the reaction aroused through association is usually different from that which would have been aroused directly1 in certain definite ways4 ,it is fainter1 and has1 when attended to1 the sort of quality that makes us call it 8imaginary04 ,in a certain class of cases1 we come to know that we can make it 8real0 if we choose2 this applies1 e4g4 to the tactual images produced by visible objects that we can touch4 ,in such cases1 the image is attached by us to the object1 and its 8imaginary0 character fails to be noticed4 ,these are the cases in which the association is not due to some accident of our experience1 but to a collocation which exists in nature4 ,in other cases1 however1 we are perfectly aware1 if we reflect1 that the association depends upon some circumstance in our private lives4 ,we may1 for instance1 have had a very interesting conversation at a certain spot1 and always think of this conversation when we find ourselves in this place4 ,but we know that the conversation does not actually take place again when we go back to where it happened4 ,in such a case1 we notice the intrinsic difference between the event as a sensible fact in the present and the event as merely revived by association4 ,i think this difference has to do with our feeling of pastness4 ,the difference which we can directly observe is not1 of course1 between our present recollection and the past conversation1 but between our present recollection and present sensible facts4 ,this difference1 combined with the inconsistency of our recollection with present facts if our recollection were placed in the present1 is perhaps a cause of our referring memories to the past4 ,but ,i offer this suggestion with hesitation2 and1 as we shall find when we have examined imagination1 it cannot be the whole truth1 though it may be part of it4 ,there are some facts that tend to support the above view4 ,in dreams1 when our critical faculty is in abeyance1 we may live past events over again under the impression that they are actually happening2 the reference of recollections to the past must1 therefore1 be a matter involving a somewhat advanced type of mental activity4 ,conversely1 we sometimes have the impression that what is happening now really happened in the past2 this is a well-known and much discussed illusion4 ,it happens especially when we are profoundly absorbed in some inward struggle or emotion1 so that outer events only penetrate faintly4 ,i suggest that1 in these circumstances1 the quality of sensations approximates to that of images1 and that this is the source of the illusion4 ,if this suggestion is right1 the feeling of pastness is really complex4 ,something is suggested by association1 but is recognisably different from a present sensible occurrence4 ,we therefore do not suppose that this something is happening now2 and we may be confirmed in this by the fact that it is inconsistent with something that is happening now4 ,we may then either refer the something to the past1 in which case we have a recollection1 though not necessarily a correct one2 or we may regard the something as purely imaginary1 in which case we have what we regard as pure imagination4 ,it remains to inquire why we do sometimes the one and sometimes the other1 which brings us to the discussion of imagination4 ,i think we shall find that memory is more fundamental than imagination1 and that the latter consists merely of memories of different dates assembled together4 ,but to support this theory will demand first an analysis of imagination and then1 in the light of this analysis1 an attempt to give further precision to our theory of memory4 ,imagination is not1 as the word might suggest1 essentially connected with images4 ,no doubt images are often1 even usually1 present when we imagine1 but they need not be4 ,a man can improvise on the piano without first having images of the music he is going to make2 a poet might write down a poem without first making it up in his head4 ,in talking1 words suggest other words1 and a man with sufficient verbal associations may be successfully carried along by them for a considerable time4 ,the art of talking without thinking is particularly necessary to public speakers1 who must go on when once they are on their feet1 and gradually acquire the habit of behaving in private as they do before an audience4 ,yet the statements they make must be admitted to be often imaginative4 ,the essence of imagination1 therefore1 does not lie in images4 ,the essence of imagination1 ,i should say1 is the absence of belief together with a novel combination of known elements4 ,in memory1 when it is correct1 the combination of elements is not novel2 and whether correct or not1 there is belief4 ,i say that in imagination there is 8a novel combination of known elements01 because1 if nothing is novel1 we have a case of memory1 while if the elements1 or any of them1 are novel1 we have a case of perception4 ,this last ,i say because ,i accept ,hume's principle that there is no 8idea0 without an antecedent 8impression04 ,i do not mean that this is to be applied in a blind and pedantic manner1 where abstract ideas are concerned4 ,i should not maintain that no one can have an idea of liberty until he has seen the ,statue of ,liberty4 ,the principle applies rather to the realm of images4 ,i certainly do not think that1 in an image1 there can be any element which does not resemble some element in a previous perception1 in the distinctive manner of images4 ,hume made himself an unnecessary difficulty in regard to the theory that images 8copy0 impressions4 ,he asked the question3 ,suppose a man has seen all the different shades of colour that go to make up the spectrum1 except just one shade4 ,to put the thing in modern language1 suppose he has never seen light of a certain small range of wave-lengths1 but has seen light of all other wave-lengths4 ,will he be able to form an image of the shade he has never seen8 ,hume thinks he will1 although this contradicts the principle4 ,i should say that images are always more or less vague copies of impressions1 so that an image might be regarded as a copy of any one of a number of different impressions of slightly different shades4 ,in order to get a test case for ,hume's question1 we should have to suppose that there was a broad band of the spectrum that the man had never seen--say the whole of the yellow4 ,he would then1 one may suppose1 be able to form images which1 owing to vagueness1 might be applicable to orange-yellow1 and others applicable to green-yellow1 but none applicable to a yellow midway between orange and green4 ,this is an example of an unreal puzzle manufactured by forgetting vagueness4 ,it is analogous to the following profound problem3 ,a man formerly hairy is now bald2 he lost his hairs one by one2 therefore there must have been just one hair that made the difference1 so that while he had it he was not bald but when he lost it he was4 ,of course 8baldness0 is a vague conception2 and so is 8copying01 when we are speaking of the way in which images copy prototypes4 ,what causes us1 in imagination1 to put elements together in a new way8 ,let us think first of concrete instances4 ,you read that a ship has gone down on a route by which you have lately travelled2 very little imagination is needed to generate the thought 8,i might have gone down04 ,what happens here is obvious3 the route is associated both with yourself and with shipwreck1 and you merely eliminate the middle term4 ,literary ability is largely an extension of the practice of which the above is a very humble example4 ,take1 say3 ,and all our yesterdays have lighted fools ,the way to dusty death4 ,out1 out1 brief candle6 ,life's but a walking shadow1 a poor player ,who struts and frets his hour upon the stage1 ,and then is heard no more4 ,it is a tale ,told by an idiot1 full of sound and fury ,signifying nothing4 ,i do not pretend to explain all the associations which led ,shakespeare to think of these lines1 but some few are obvious4 8,dusty death0 is suggested by ,genesis iii4 #ai3 8,dust thou art1 and unto dust shalt thou return04 ,having spoken of 8lighting fools the way01 it is natural to think of a 8candle01 and thence of a 8walking shadow0 being lighted by the candle along the way4 ,from shadows to players was a well-established association in ,shakespeare's mind2 thus in ,midsummer ,night's ,dream he says of players3 8,the best in this kind are but shadows1 and the worst are no worse1 if imagination amend them04 ,from a 8poor player0 to a 8tale told by an idiot0 is no very difficult transition for a theatre-manager2 and 8sound and fury0 no doubt often formed part of the tales to which he had to listen in spite of their 8signifying nothing04 ,if we knew more about ,shakespeare1 we could explain more of him in this sort of way4 ,thus exceptional imaginative gifts appear to depend mainly upon associations that are unusual and have an emotional value owing to the fact that there is a certain uniform emotional tone about them4 ,many adjectives are suitable to death3 in a mood quite different from ,macbeth's1 it may be called 8noble1 puissant and mighty04 ,a ,chancellor of the ,exchequer1 thinking of the ,death ,duties1 might feel inclined to speak of 8lucrative death02 nevertheless he would not1 like ,vaughan1 speak of 8dear1 beauteous death04 ,shakespeare also would not have spoken of death in such terms1 for his view of it was pagan2 he speaks of 8that churl death04 ,so a man's verbal associations may afford a key to his emotional reactions1 for often what connects two words in his mind is the fact that they rouse similar emotions4 ,the absence of belief that accompanies imagination is a somewhat sophisticated product2 it fails in sleep and in strong and emotional excitement4 ,children invent terrors for fun1 and then begin to believe in them4 ,the state of entertaining an idea without believing it is one involving some tension1 which demands a certain level of intellectual development4 ,it may be assumed that imagination1 at first1 always involved belief1 as it still does in dreams4 ,i am not concerned at the moment to define 8belief01 but a criterion is influence on action4 ,if ,i say 8suppose there were a tiger outside your front door01 you will remain calm2 but if ,i say1 with such a manner as to command belief1 8there is a tiger outside your front door01 you will stay at home1 even if it involves missing your train to the office4 ,this illustrates what ,i mean when ,i say that imagination1 in its developed form1 involves absence of belief4 ,but this is not true of its primitive forms4 ,and even a civilised adult1 passing through a churchyard on a dark night1 may feel fear if his imagination turns in the direction of ghosts4 ,when imagination passes into belief1 it does not1 as a rule1 become a belief about the past4 ,generally we place the imagined object in the present1 but not where it would be perceptible to our senses4 ,if we place it in the past1 it is because the past has some great emotional significance for us4 ,if a person we love has been in great danger1 and we do not know whether he has come through safely1 imagination of his death may lead us to believe that he has been killed4 ,and often imagination leads us to believe that something is going to happen4 ,what is common to all such cases is the emotional interest3 this first causes us to imagine an event1 and then leads us to think that it has happened1 is happening1 or will happen1 according to the circumstances4 ,hope and fear have this effect equally2 wish-fulfilment and dread-fulfilment are equally sources of dreams and day-dreams4 ,a great many beliefs have a source of this kind4 ,but1 in spite of psycho-analysis1 there are a great many that have a more rational foundation4 ,i believe that ,columbus first crossed the ocean in #adib1 though #adia or #adic would have suited me just as well4 ,i cannot discover that there is any emotional element in this belief1 or in the belief that ,semipalatinsk is in ,central ,asia4 ,the view that all our beliefs are irrational is perhaps somewhat overdone nowadays1 though it is far more nearly true than the views that it has displaced4 ,we must now return to the subject of memory4 ,memory proper does not1 like imagination1 involve a re-arrangement of elements derived from past experience2 on the contrary1 it should restore such elements in the pattern in which they occurred4 ,this is the vital difference between memory and imagination2 belief1 even belief involving reference to the past1 may1 as we have seen1 be present in what is really imagination though it may not seem to be so to the person concerned4 ,that being so1 we still have to consider what constitutes the reference to the past1 since the view tentatively suggested before we had considered imagination turns out to be inadequate4 ,there is one possible view1 suggested1 though not definitely adopted1 by ,dr4 ,broad in his chapter on 8,memory0 already referred to4 ,according to this view1 we have to start from temporal succession as perceived within what is called the 8specious present01 i4e4 a short period of time such that the events that occur throughout it can be perceived together4 7,i shall return to this subject presently47 ,for example1 you can see a quick movement as a whole2 you are not merely aware that the object was first in one place and then in another4 ,you can see the movement of the second-hand of a watch1 but not of the hour-hand or minute-hand4 ,when you see a movement in this sense1 you are aware that one part of it is earlier than another4 ,thus you acquire the idea 8earlier01 and you can mean by 8past0 8earlier than this01 where 8this0 is what is actually happening4 ,this is a logically possible theory1 but it seems nevertheless somewhat difficult to believe4 ,i do not know1 however1 of any easier theory1 and ,i shall therefore adopt it provisionally while waiting for something better4 ,for the understanding of memory1 it is a help to consider the links connecting its most developed forms with other occurrences of a less complex kind4 ,true recollection comes at the end of a series of stages4 ,i shall distinguish five stages on the way1 so that recollection becomes the sixth in gradual progress4 ,the stages are as follows3 #a4 ,images4--,as we have seen1 images1 at any rate in their simpler parts1 in fact copy past sensations more or less vaguely1 even when they are not known to do so4 ,images are 8mnemic0 phenomena1 in the sense that they are called up by stimuli formerly associated with their prototypes1 so that their occurrence is a result of past experience according to the law of association4 ,but obviously an image which in fact copies a past occurrence does not constitute a recollection unless it is felt to be a copy4 #b4 ,familiarity4--,images and perceptions may come to us1 and so may words or other bodily movements1 with more or less of the feeling we call 8familiarity04 ,when you recall a tune that you have heard before1 either by images or by actually singing it1 part of what comes to you may feel familiar1 part unfamiliar4 ,this may lead you to judge that you have remembered the familiar part rightly and the unfamiliar part wrongly1 but this judgment belongs to a later stage4 #c4 ,habit-,memory4--,we have already discussed this in ,chapter ,,vi4 ,people say they remember a poem if they can repeat it correctly4 ,but this does not necessarily involve any recollection of a past occurrence2 you may have quite forgotten when and where you read the poem4 ,this sort of memory is mere habit1 and is essentially like knowing how to walk although you cannot remember learning to walk4 ,this does not deserve to be called memory in the strict sense4 #d4 ,recognition4--,this has two forms4 7a7 ,when you see a dog1 you can say to yourself 8there is a dog01 without recalling any case in which you have seen a dog before1 and even without reflecting that there have been such cases4 ,this involves no knowledge about the past2 essentially it is only an associative habit4 7b7 ,you may know 8,i saw this before01 though you do not know when or where1 and cannot recollect the previous occurrence in any way4 ,in such a case there is knowledge about the past1 but it is very slight4 ,when you judge3 8,i saw this before01 the word 8this0 must be used vaguely1 because you did not see exactly what you see now1 but only something very like this4 ,thus all that you are really knowing is that1 on some past occasion1 you saw something very like what you are seeing now4 ,this is about the minimum of knowledge about the past that actually occurs4 #e4 ,immediate ,memory4--,i come now to a region intermediate between sensation and true memory1 the region of what is sometimes called 8immediate memory04 ,when a sense-organ is stimulated1 it does not1 on the cessation of the stimulus1 return at once to its unstimulated condition3 it goes on 7so to speak7 vibrating1 like a piano-string1 for a short time4 ,for example1 when you see a flash of lightning1 your sensation1 brief as it is1 lasts much longer than the lightning as a physical occurrence4 ,there is a period during which a sensation is fading3 it is then called an 8acoleuthic0 sensation4 ,it is owing to this fact that you can see a movement as a whole4 ,as observed before1 you cannot see the minute-hand of a watch moving1 but you can see the second-hand moving4 ,that is because it is in several appreciably different places within the short time that is required for one visual sensation to fade1 so that you do actually1 at one moment1 see it in several places4 ,the fading sensations1 however1 feel different from those that are fresh1 and thus the various positions which are all sensibly present are placed in a series by the degree of fading1 and you acquire the perception of movement as a process4 ,exactly the same considerations apply to hearing a spoken sentence4 ,thus not only an instant1 but a short finite time is sensibly present to you at any moment4 ,this short finite time is called the 8specious present04 ,by the felt degree of fading1 you can distinguish earlier and later in the specious present1 and thus experience temporal succession without the need of true memory4 ,if you see me quickly move my arm from left to right1 you have an experience which is quite different from what you would have if you now saw it at the right and remembered that a little while ago you saw it at the left4 ,the difference is that1 in the quick movement1 the whole falls within the specious present1 so that the entire process is sensible4 ,the knowledge of something as in the immediate past1 though still sensible1 is called 8immediate memory04 ,it has great importance in connection with our apprehension of temporal processes1 but cannot count as a form of true memory4 #f4 ,true ,recollection4--,we will suppose1 for the sake of definiteness1 that ,i am remembering what ,i had for breakfast this morning4 ,there are two questions which we must ask about this occurrence3 7a7 ,what is happening now when ,i recollect8 7b7 ,what is the relation of the present happening to the event remembered8 ,as to what is happening now1 my recollection may involve either images or words2 in the latter case1 the words themselves may be merely imagined4 ,i will take the case in which there are images without words1 which must be the more primitive1 since we cannot suppose that memory would be impossible without words4 ,the first point is one which seems so obvious that ,i should be ashamed to mention it1 but for the fact that many distinguished philosophers think otherwise4 ,the point is this3 whatever may be happening now1 the event remembered is not happening4 ,memory is often spoken of as if it involved the actual persistence of the past which is remembered2 ,bergson1 e4g4 speaks of the interpenetration of the present by the past4 ,this is mere mythology2 the event which occurs when ,i remember is quite different from the event remembered4 ,people who are starving can remember their last meal1 but the recollection does not appease their hunger4 ,there is no mystic survival of the past when we remember2 merely a new event having a certain relation to the old one4 ,what this relation is1 we shall consider presently4 ,it is quite clear that images are not enough to constitute recollection1 even when they are accurate copies of a past occurrence4 ,one may1 in a dream1 live over again a past experience2 while one is dreaming1 one does not seem to be recalling a previous occurrence1 but living through a fresh experience4 ,we cannot be said to be remembering1 in the strict sense1 unless we have a belief referring to the past4 ,images which1 like those in dreams1 feel as if they were sensations1 do not constitute recollection4 ,there must be some feeling which makes us refer the images to a past prototype4 ,perhaps familiarity is enough to cause us to do so4 ,and perhaps this also explains the experience of trying to remember something and feeling that we are not remembering it right4 ,parts of a complex image may feel more familiar than other parts1 and we then feel more confidence in the correctness of the familiar parts than in that of the others4 ,the conviction that the image we are forming of a past event is wrong might seem to imply that we must be knowing the past otherwise than by images1 but ,i do not think this conclusion is really warranted1 since degrees of familiarity in images suffice to explain this experience4 7b7 ,what is the relation of the present happening to the event remembered8 ,if we recollect correctly1 the several images will have that kind of resemblance of quality which images can have to their prototypes1 and their structure and relations will be identical with those of their prototypes4 ,suppose1 for instance1 you want to remember whether1 in a certain room1 the window is to the right or left of the door as viewed from the fireplace4 ,you can observe your image of the room1 consisting 7inter alia7 of an image of the door and an image of the window standing 7if your recollection is correct7 in the same relation as when you are actually seeing the room4 ,memory will consist in attaching to this complex image the sort of belief that refers to the past2 and the correctness of memory consists of similarity of quality and identity of structure between the complex image and a previous perception4 ,as for the trustworthiness of memory1 there are two things to be said4 ,taken as a whole1 memory is one of the independent sources of our knowledge2 that is to say1 there is no way of arriving at the things we know through memory by any argument wholly derived from things known otherwise4 ,but no single memory is obliged to stand alone1 because it fits1 or does not fit1 into a system of knowledge about the past based upon the sum-total of memories4 ,when what is remembered is a perception by one or more of the public senses1 other people may corroborate it4 ,even when it is private1 it may be confirmed by other evidence4 ,you may remember that you had a toothache yesterday1 and that you saw the dentist to-day2 the latter fact may be confirmed by an entry in your diary4 ,all these make a consistent whole1 and each increases the likelihood of the other4 ,thus we can test the truth of any particular recollection1 though not of memory as a whole4 ,to say that we cannot test the truth of memory as a whole is not to give a reason for doubting it1 but merely to say that it is an independent source of knowledge1 not wholly replaceable by other sources4 ,we know that our memory is fallible1 but we have no reason to distrust it on the whole after sufficient care in verification has been taken4 ,the causation of particular acts of recollection seems to be wholly associative4 ,something in the present is very like something in the past1 and calls up the context of the past occurrence in the shape of images or words2 when attention falls upon this context1 we believe that it occurred in the past1 not as mere images1 and we then have an act of recollection4 ,there are many difficult problems connected with memory which ,i have not discussed1 because they have an interest which is more purely psychological than philosophical4 ,it is memory as a source of knowledge that specially concerns the philosopher4 ,,chapter ,,xix ,,the ,,introspective ,,analysis ,,of ,,perception ,we have considered perception already from the behaviourist standpoint1 and also from that of physics4 ,in the present chapter we are to consider it from the standpoint of self-observation1 with a view to discovering as much as we can about the intrinsic character of the event in us when we perceive4 ,i shall begin with certain traditional doctrines as to mental events1 and shall thence pass to the doctrines that ,i wish to advocate4 ,the words 8mind0 and 8matter0 are used glibly1 both by ordinary people and by philosophers1 without any adequate attempt at definition4 ,philosophers are much to blame for this4 ,my own feeling is that there is not a sharp line1 but a difference of degree2 an oyster is less mental than a man1 but not wholly un-mental4 ,and ,i think 8mental0 is a character1 like 8harmonious0 or 8discordant01 that cannot belong to a single entity in its own right1 but only to a system of entities4 ,but before defending this view1 ,i wish to spend some time on the theories that have been current in the past4 ,traditionally1 there are two ways of becoming aware that something exists1 one by the senses1 the other by what is called 8introspection01 or what ,kant called the 8inner sense04 ,by means of introspection1 it is maintained1 we become aware of occurrences quite different in kind from those perceived through the outer senses4 ,occurrences known through introspection are traditionally called 8mental01 and so are any other occurrences which intrinsically resemble them4 ,mental occurrences are traditionally of three main types1 called knowing1 willing1 and feeling4 8,feeling01 in this connection1 means pleasure and unpleasure--we do not say 8pleasure and pain01 because 8pain0 is an ambiguous word3 it may stand for painful sensation1 as when you say 8,i have a pain in my tooth01 or it may stand for the unpleasant character of the sensation4 ,roughly pleasure is a quality which makes you want an experience to continue1 and unpleasure is the opposite quality which makes you want an experience to stop4 ,however1 ,i am not concerned to enlarge upon feeling at present4 ,as for the other two kinds of mental occurrence1 8knowing0 and 8willing0 are recognised as too narrow to describe what is meant4 ,philosophers wish to include not only knowledge but also error1 and not only the sort of knowledge that is expressed in beliefs but also the sort that occurs in perception4 ,the word 8cognition0 or 8cognitive state0 is used to cover everything that could possibly be described as either knowledge or error2 perception is prima facie included1 but pure sensation is more debatable4 8,willing01 again1 is too narrow a term4 ,a term is required which will include desire and aversion1 and generally those states of mind which lead up to action4 ,these are all included under the head of 8conation01 a technical term invented for this special purpose4 ,cognition and conation both have1 in the orthodox theory1 the property of being directed to an object4 ,what you perceive or believe1 what you desire or will1 is something different from your state of mind4 ,to take instances3 you remember a past event1 but your remembering occurs now2 therefore your remembering is a different occurrence from what you remember4 ,you will to move your arm1 but the movement is a physical occurrence1 and therefore obviously different from your volition4 ,many psychologists have taken this relation to an object as the essential characteristic of mind--notably the two ,austrians ,brentano and ,meinong4 ,sometimes feeling also is regarded as having an object3 it is held that we are pleased or displeased at something4 ,this view1 however1 has never won general acceptance1 whereas the view that cognition and conation are directed to objects may be regarded as orthodox4 ,it is undeniable that this characteristic of being directed to objects is1 in some sense1 a property of cognition and conation1 but there is room for great difference of opinion as to the proper analysis of the property4 ,i think we cannot hope to understand the word 8mental0 until we have undertaken this analysis1 and ,i shall therefore proceed to address myself to it4 ,i shall confine myself to cognition1 which is more important for our present purposes than conation4 ,as regards cognition1 though philosophers have disagreed widely1 ,i think that1 until recently1 most would have assented to at least the following paragraph3 ,cognition is of various sorts4 ,take1 as important kinds1 perception1 memory1 conception1 and beliefs involving concepts4 ,perception is the ordinary awareness of sensible objects3 seeing a table1 hearing a piano1 and so on4 ,memory is awareness of a past occurrence1 when this awareness is direct1 not inferred or derived from testimony4 ,conception is more difficult to characterise4 ,one may say1 as a way of pointing out what is intended1 that we 8conceive0 whenever we understand the meaning of an abstract word1 or think of that which is in fact the meaning of the word4 ,if you see a white patch of snow1 or recall it by means of images1 you do not have a concept2 but if you think about whiteness1 you have a concept4 ,similarly if1 after seeing a number of coins1 you think about roundness as a common characteristic of all of them1 you have a concept4 ,the object of your thought1 in such a case1 is a universal or a ,platonic idea4 ,every sentence must contain at least one word expressing a concept1 and therefore every belief that can be expressed in words contains concepts4 ,each of these kinds of cognitive attitude involves its own problems4 ,in the present chapter we are concerned with perception4 ,this has to be treated both introspectively and causally2 it is the introspective treatment that we have now to undertake4 ,when you have the experience called 8seeing a table01 there is a certain amount of difference between your unreflecting judgment and what careful examination reveals as to the nature of your experience4 ,you judge that the table is rectangular1 but the patch of colour in your visual field is not a rectangle2 when you learn to draw1 you have to draw the table as it really seems and not as it seems to seem4 ,you have images of sensations of touch2 if you were to try to touch the table and it turned out to be an optical illusion1 you would get a violent shock of surprise4 ,you have also expectations of a certain degree of permanence and weight4 ,if you went to lift the table1 you would find your muscles quite wrongly adjusted if the table were much lighter than it looked4 ,all these elements must be included in the perception1 though not in the sensation4 8,sensation01 as opposed to perception1 is more or less hypothetical4 ,it is supposed to be the core1 in the perception1 which is solely due to the stimulus and the sense-organ1 not to past experience4 ,when you judge that the table is rectangular1 it is past experience that enables and compels you to do so2 if you had been born blind and just operated upon1 you could not make this judgment4 ,nor would you have expectations of hardness1 etc4 ,but none of this can be discovered by introspection4 ,from an introspective point of view1 the elements due to past experience are largely indistinguishable from those due to the stimulus alone4 ,one supposes that past experience modifies the brain1 and thereby modifies the mental occurrence due to the stimulus4 ,the notion of sensation as opposed to perception belongs1 therefore1 to the causal study of perception1 not to the introspective study4 ,there is1 however1 a distinction to be made here4 ,you can discover by mere self-observation that visual objects are accompanied by expectations or images of touch2 and similarly if you touch an object in the dark you will probably be led to form some visual image of it4 ,here you can arrive at a certain degree of analysis of your perception through the fact that images1 as a rule1 feel different from the immediate results of a sensory stimulus4 ,on the other hand1 no amount of introspection alone will reveal such things as the blind spot4 ,the filling in of a sensation by elements belonging to the same sense is much less discoverable by introspection than the filling in by associated images belonging to other senses4 ,thus although by introspection alone we could discover part of the influence of experience on perception1 there is another part which we cannot discover in this way4 ,remaining in the introspective attitude1 it is evident that the contents of our minds at any given moment are very complex4 ,throughout our normal waking life we are always seeing1 hearing1 and touching1 sometimes smelling and tasting1 always having various bodily sensations1 always feeling pleasant or unpleasant feelings 7usually both71 always having desires or aversions4 ,we are not normally aware of all these items1 but we can become aware of any of them by turning our attention in the right direction4 ,i am not at present discussing 8unconscious mental states01 because they1 obviously1 can only be known causally1 and we are now considering what can be known introspectively4 ,there may be any number of perceptions that cannot be known by introspection2 the point for us1 at the moment1 is that those that can be discovered by introspection at any one time are many and various4 ,i do not wish1 just now1 to discuss the nature of attention2 ,i wish only to point out that it enables us to take the first steps in abstraction4 ,out of the whole multiplicity of objects of sense1 it enables us to single out a small selection1 which is an indispensable preliminary to abstraction4 ,for example1 attention will enable us to discriminate a coloured pattern which we are seeing1 and to separate it from the other things we see and from images and other objects of sense and thoughts which may exist simultaneously4 ,for the sake of simplicity1 let us suppose that we discriminate a black and white pattern in the form of a triangle4 ,within this pattern we can further discriminate sides and angles and an inside and outside--of course the sides are not mathematical lines nor the angles mathematical points4 ,we now come to a question of very great importance1 upon which our views of the relations of mind and matter largely depend4 ,the question is this3 ,what difference is there between the propositions 8there is a triangle0 and 8,i see a triangle08 ,both these statements seem as certain as any statement can be--at least if rightly interpreted4 ,as always happens in such cases1 we are quite certain of something1 but not quite certain what it is that we are certain of4 ,i want to ask whether this something that we are certain of is really different in the above two statements1 or whether the difference between them is only as to surroundings of which we are not certain4 ,most philosophers hold that there is a difference in what we are certain of2 ,mach1 ,james1 ,dewey1 the ,american realists1 and ,i hold that the difference is in the uncertain context4 ,let us examine this question4 ,the suggestions of the two statements 8,i see a triangle0 and 8there is a triangle0 are obviously different4 ,the first states an event in my life1 and suggests its possible effects upon me4 ,the second aims at stating an event in the world1 supposed to be equally discoverable by other people4 ,you might say 8there is a triangle0 if you had seen it a moment ago but now had your eyes shut2 in this case you would not say 8,i see a triangle04 ,on the other hand1 one sometimes1 under the influence of indigestion or fatigue1 sees little black dots floating in the air2 in such circumstances you would say 8,i see a black dot01 but not 8there is a black dot04 ,this illustration shows that when you say 8there is a black dot0 you are making a stronger assertion than when you say 8,i see a black dot04 ,in the other case1 when you say 8there is a triangle0 because you saw it a moment ago1 though not now1 you have three stages3 ,first1 memory assures you of the proposition 8,i saw a triangle01 and then you pass on to 8there was a triangle01 and then1 further1 to 8there is a triangle1 because nothing can have happened to destroy it so quickly40 ,here we have obviously passed far beyond the region of immediate certainty4 ,it seems clear1 therefore1 that1 of our two statements1 the one which comes nearest to expressing the fact of which we are immediately certain is 8,i see a triangle01 because the other makes inferences to something public1 and thus goes beyond the bare datum4 ,this is on the assumption that we should not say 8there is a black dot0 when we see a black dot which we attribute to eye-trouble and therefore suppose that no one else can see4 ,let us therefore concentrate upon 8,i see a triangle01 and ask ourselves whether the whole of this1 or only part1 can be accepted as a primitive certainty4 ,a moment's reflection shows that both 8,i0 and 8see0 are words which take us beyond what the momentary event reveals4 ,take 8,i0 to begin with4 ,this is a word whose meaning evidently depends upon memory and expectation4 8,i0 means the person who had certain remembered experiences and is expected to have certain future experiences4 ,we might say 8,i see a triangle now and ,i saw a square a moment ago40 ,the word 8,i0 has exactly the same meaning in its two occurrences in this sentence1 and therefore evidently has a meaning dependent upon memory4 ,now it is our object to arrive at the contribution to your knowledge which is made by seeing the triangle at the moment4 ,therefore1 since the word 8,i0 takes you beyond this contribution1 we must cut it out if we want to find a correct verbal expression for what is added to our knowledge by seeing the triangle4 ,we will say 8a triangle is being seen04 ,this is at any rate one step nearer to what we are seeking4 ,but now we must deal with the word 8seen04 ,as ordinarily used1 this is a causal word1 suggesting something dependent upon the eyes4 ,in this sense1 it obviously involves a mass of previous experience2 a new-born baby does not know that what it sees depends upon its eyes4 ,however1 we could eliminate this4 ,obviously all objects of sight have a common quality1 which no objects of touch or hearing have2 a visual object is different from an auditory object1 and so on4 ,therefore instead of saying 8a triangle is being seen01 we should say 8there is a visual triangle04 ,of course the meanings of the words 8visual0 and 8triangle0 can only be learnt by experience1 but they are not logically dependent upon experience4 ,a being could be imagined which would know the words at birth2 such a being could express its datum in the words 8there is a visual triangle04 ,in any case1 the problems remaining belong to the study of concepts2 we will therefore ignore them at present4 ,now in ,english the words 8there is0 are ambiguous4 ,when ,i used them before1 saying1 8there is a triangle01 ,i meant them in the sense of 8voila0 or 8da ist04 ,now ,i mean them in the sense of 8il y a0 or 8es giebt04 ,one might express what is meant by saying 8a visual triangle exists01 but the word 8exist0 has all sorts of metaphysical connotations that ,i wish to avoid4 ,perhaps it is best to say 8occurs04 ,we have now arrived at something which is just as true when your perception is illusory as when it is correct4 ,if you say 8a visual black dot is occurring01 you are speaking the truth1 if there is one in your field of vision4 ,we have eliminated the suggestion that others could see it1 or that it could be touched1 or that it is composed of matter in the sense of physics4 ,all these suggestions are present when one says1 in ordinary conversation1 8there is a black dot02 they are intended to be eliminated by the addition of the word 8visual0 and the substitution of 8is occurring0 for 8there is04 ,by these means we have arrived at what is indubitable and intrinsic in the addition to your knowledge derived from a visual datum4 ,we must now ask ourselves once more3 ,is there still a distinction1 within what is immediate and intrinsic1 between the occurrence of a visual datum and the cognition of it8 ,can we say1 on the basis of immediate experience1 not only 8a visual black dot occurs01 but also 8a visual black dot is cognised08 ,my feeling is that we cannot4 ,when we say that it is cognised1 we seem to me to mean that it is part of an experience1 that is to say1 that it can be remembered1 or can modify our habits1 or1 generally1 can have what are called 8mnemic0 effects4 ,all this takes us beyond the immediate experience into the realm of its causal relations4 ,i see no reason to think that there is any duality of subject and object in the occurrence itself1 or that it can properly be described as a case of 8knowledge04 ,it gives rise to knowledge1 through memory1 and through conscious or unconscious inferences to the common correlates of such data4 ,but in itself it is not knowledge1 and has no duality4 ,the datum is a datum equally for physics and for psychology2 it is a meeting point of the two4 ,it is neither mental nor physical1 just as a single name is neither in alphabetical order nor in order of precedence2 but it is part of the raw material of both the mental and the physical worlds4 ,this is the theory which is called 8neutral monism01 and is the one that ,i believe to be true4 ,,chapter ,,xx ,,consciousness8 ,twenty-three years have elapsed since ,william ,james startled the world with his article entitled 8,does #8consciousness' exist80 ,in this article1 reprinted in the volume called ,essays in ,radical ,empiricism1 he set out the view that 8there is only one primal stuff or material in the world01 and that the word 8consciousness0 stands for a function1 not an entity4 ,he holds that there are 8thoughts01 which perform the function of 8knowing01 but that thoughts are not made of any different 8stuff0 from that of which material objects are made4 ,he thus laid the foundations for what is called 8neutral monism01 a view advocated by most ,american realists4 ,this is the view advocated in the present volume4 ,in this chapter1 we have to ask ourselves whether there is anything that we can call 8consciousness0 in any sense involving a peculiar kind of stuff1 or whether we can agree with ,william ,james that there is no 8inner duplicity0 in the stuff of the world as we know it1 and that the separation of it into knowing and what is known does not represent a fundamental dualism4 ,there are two very different meanings attached to the word 8consciousness0 by those who use it4 ,on the one hand1 we are said to be 8conscious of0 something2 in this sense1 8consciousness0 is a relation4 ,on the other hand1 8consciousness0 may be regarded as a quality of mental occurrences1 not consisting in their relation to other things4 ,let us take the first view first1 since1 in discussing it1 we shall find reasons for rejecting the second view4 ,what is the relation we call being 8conscious of0 something8 ,take the difference between a person awake and a person asleep4 ,the former reacts to all kinds of stimuli to which the latter does not react2 we therefore say that the latter is not 8conscious of0 what is happening in his neighbourhood4 ,but even if the sleeper does react in a fashion1 for example1 by turning away from the light1 such a reaction does not fall within what is commonly regarded as 8knowledge0 or 8awareness02 we should say that the sleeper turned over 8unconsciously04 ,if he wakes up sufficiently to speak intelligently1 for instance to address the disturber by name1 we consider him 8conscious04 ,so we do if we find that he remembers the incident next morning4 ,but common sense does not regard any and every bodily movement in response to a stimulus as evidence of 8consciousness04 ,there is no doubt1 ,i think1 that common sense regards certain kinds of response as evidence of some 8mental0 process caused by the stimulus1 and regards the 8consciousness0 as residing in the inferred 8mental0 occurrence4 ,sometimes1 however1 as in hypnotism and sleep-walking1 people refuse to admit 8consciousness0 even where many of the usual marks of it are present4 ,for this there are certain reasons4 ,one of them is subsequent lack of memory2 another is lack of intelligence in what is being done4 ,if you offer a hypnotised patient a drink of ink1 telling him it is port wine1 and he drinks it up with every sign of enjoyment1 you say that he is not 8conscious01 because he does not react normally to the nasty taste4 ,it would seem better1 however1 to say that he is conscious of the hypnotist and what he commands1 though not of other things of which he would be conscious in a normal condition4 ,and lack of subsequent memory is a very difficult criterion1 since we normally forget many things that have happened to us1 and the sleep-walker's forgetting is only unusually complete4 ,this is obviously a matter of degree4 ,take next morning's memories in the case of a man who was drunk overnight4 ,they become more and more vague as he reviews the later hours of the evening1 but there is no sharp line where they cease abruptly4 ,thus1 if memory is a test1 consciousness must be a matter of degree4 ,i think that here1 again1 common sense regards a certain amount of memory as necessary evidence to prove that there were 8mental0 processes at the time of the acts in question1 acts in sleep being regarded as not involving 8mind01 and other acts in certain abnormal conditions being supposed to resemble those of sleep in this respect4 ,it follows that1 if we are to find out what is commonly meant by 8consciousness01 we must ask ourselves what is meant by a 8mental0 occurrence4 ,not every mental occurrence1 however1 is in question4 ,the only kinds concerned are those which seem to have relation to an 8object04 ,a feeling of pleasant drowsiness would commonly count as 8mental01 but does not involve 8consciousness0 of an 8object04 ,it is this supposed peculiar relation to an 8object0 that we have to examine4 ,we may take1 as the best example1 an ordinary act of perception4 ,i see1 let us say1 a table1 and ,i am convinced that the table is outside me1 whereas my seeing of it is a 8mental0 occurrence1 which is inside me4 ,in such a case ,i am 8conscious0 of the table--so at least common sense would say4 ,and since ,i cannot see without seeing something1 this relation to an 8object0 is of the very essence of seeing4 ,the same essential relation to an 8object01 it would be said1 is characteristic of every kind of consciousness4 ,but when we begin to consider this view more closely1 all sorts of difficulties arise4 ,we have already seen that1 on grounds derived from physics1 the table itself1 as a physical thing1 cannot be regarded as the object of our perception1 if the object is something essential to the existence of the perception4 ,in suitable circumstances1 we shall have the same perception although there is no table4 ,in fact1 there is no event outside the brain which must exist whenever we 8see a table04 ,it seems preposterous to say that when we think we see a table we really see a motion in our own brain4 ,hence we are led to the conclusion that the 8object0 which is essential to the existence of an act of perception is just as 8mental0 as the perceiving4 ,in fact1 so this theory runs1 the mental occurrence called 8perceiving0 is one which contains within itself the relation of perceiver and perceived1 both sides of the relation being equally 8mental04 ,now1 however1 there seems no longer any reason to suppose that there is any essentially relational character about what occurs in us when we perceive4 ,the original reason for thinking so was the naively realistic view that we see the actual table4 ,if what we see is as mental as our seeing1 why distinguish between the two8 ,the coloured pattern that we see is not really 8out there01 as we had supposed2 it is in our heads1 if we are speaking of physical space4 ,true1 more than a coloured pattern occurs when we 8see a table04 ,there are tactual expectations or images3 there is probably belief in an external object2 and afterwards there may be memory or other 8mnemic0 effects4 ,all this may be taken as representing what the above theory took to be the 8subject0 side of an act of perception1 while the coloured pattern is what the theory took to be the 8object0 side4 ,but both sides are on a level as regards being 8mental04 ,and the relation between the two sides is not of such a kind that the existence of the one logically demands the existence of the other2 on the contrary1 the relation between the two sides is causal1 being dependent upon experience and the law of association4 ,if this is correct1 what really happens when1 as common sense would say1 we are conscious of a table1 is more or less as follows4 ,first there is a physical process external to the body1 producing a stimulus to the eye which occurs rarely 7not never7 in the absence of an actual physical table4 ,then there is a process in the eye1 nerves1 and brain1 and finally there is a coloured pattern4 ,this coloured pattern1 by the law of association1 gives rise to tactual and other expectations and images2 also1 perhaps1 to memories and other habits4 ,but everything in this whole series consists of a causally continuous chain of events in space-time1 and we have no reason to assert that the events in us are so very different from the events outside us--as to this1 we must remain ignorant1 since the outside events are only known as to their abstract mathematical characteristics1 which do not show whether these events are like 8thoughts0 or unlike them4 ,it follows that 8consciousness0 cannot be defined either as a peculiar kind of relation or as an intrinsic character belonging to certain events and not to others4 8,mental0 events are not essentially relational1 and we do not know enough of the intrinsic character of events outside us to say whether it does or does not differ from that of 8mental0 events4 ,but what makes us call a certain class of events 8mental0 and distinguish them from other events is the combination of sensitivity with associative reproduction4 ,the more markedly this combination exists1 the more 8mental0 are the events concerned2 thus mentality is a matter of degree4 ,there is1 however1 a further point which must be discussed in this connection1 and that is 8self-consciousness01 or awareness of our own 8mental0 events4 ,we already had occasion to touch on this in ,chapter ,,xvi in connection with ,descartes' 8,i think1 therefore ,i am04 ,but ,i want to discuss the question afresh in connection with 8consciousness04 ,when the plain man sees 8a table0 in the presence of a philosopher1 the plain man can be driven1 by the arguments we have repeatedly brought forward1 to admit that he cannot have complete certainty as to anything outside himself4 ,but if he does not lose his head or his temper1 he will remain certain that there is a coloured pattern1 which may be in him1 but indubitably exists4 ,no argument from logic or physics even tends to show that he is mistaken in this2 therefore there is no reason why he should surrender his conviction4 ,the argument about knowledge in ,chapter ,,viii showed that1 accepting the usual views of physicists as to causal laws1 our knowledge becomes more certain as the causal chain from object to reaction is shortened1 and can only be quite certain when the two are in the same place in space-time1 or at least contiguous4 ,thus we should expect that the highest grade of certainty would belong to knowledge as to what happens in our own heads4 ,and this is exactly what we have when we are aware of our own 8mental0 events1 such as the existence of a coloured pattern when we thought we were seeing a table4 ,we might1 therefore1 if we were anxious to preserve the word 8mental01 define a 8mental0 event as one that can be known with the highest grade of certainty1 because1 in physical space-time1 the event and the knowing of it are contiguous4 ,thus 8mental0 events will be certain of the events that occur in heads that have brains4 ,they will not be all events that occur in brains1 but only such as cause a reaction of the kind that can be called 8knowledge04 ,there are1 however1 still a number of difficult questions1 to which1 as yet1 a definitive answer cannot be given4 ,when we 8know0 a thought of our own1 what happens8 ,and do we know the thought in a more intimate way than we know anything else8 ,knowledge of external events1 as we have seen1 consists of a certain sensitivity to their presence1 but not in having in or before our minds anything similar to them1 except in certain abstract structural respects4 ,is knowledge of our own minds equally abstract and indirect8 ,or is it something more analogous to what we ordinarily imagine knowledge to be8 ,take first the question3 ,what happens when we 8know0 a thought of our own8 ,taking the definition of 8knowing0 that we adopted in ,chapter ,,viii1 we shall say3 ,we 8know0 a thought of our own when an event in our brain causes a characteristic reaction which is present when the event occurs and not otherwise4 ,in this sense1 whenever we say1 8,i see a table01 we are knowing a thought1 since an event in our brain is the only invariable antecedent of such a statement 7assuming it to be made truthfully74 ,we may think we are knowing a table1 but this is an error4 ,thus the difference between introspective and other knowledge is only in our intention and in the degree of certainty4 ,when we say1 8,i see a table01 we may intend to know an external object1 but if so we may be mistaken2 we are1 however1 actually knowing the occurrence of a visual percept4 ,when we describe the same occurrence in the words 8a certain coloured pattern is occurring01 we have changed our intention and are much more certain of being right4 ,thus all that differentiates our reaction when it gives introspective knowledge from our reaction when it gives knowledge of another kind is the elimination of a possible source of error4 ,i come now to the question3 ,do we know our own thoughts in a more intimate way than we know anything else8 ,this is a question to which it is difficult to give precision2 it describes something that one feels to be a problem without being able to say exactly what the problem is4 ,however1 some things can be said which may serve to clear up our feelings1 if not our ideas4 ,suppose you are asked to repeat after a man whatever he says1 as a test of your hearing4 ,he says 8how do you do80 and you repeat 8how do you do80 ,this is your knowledge-reaction1 and you hear yourself speaking4 ,you can perceive that what you hear when you speak is closely similar to what you hear when the other man speaks4 ,this makes you feel that your reaction reproduces accurately what you heard4 ,your knowledge-reaction1 in this case1 is the cause of an occurrence closely similar to the occurrence that you are knowing4 ,moreover1 our inveterate naive realism makes us think that what we said was what we heard while we were speaking4 ,this is1 of course1 an illusion1 since an elaborate chain of physical and physiological causation intervenes between speaking and hearing oneself speak2 nevertheless1 the illusion re-enforces our conviction that our knowledge1 in such a case1 is very intimate4 ,and it is1 in fact1 as intimate as it can hope to be1 when our knowledge-reaction reproduces the very event we are knowing1 or at least an event extremely similar to it4 ,this may be the case on other occasions1 but we can only know1 with any certainty1 that it is the case when what is known is a percept4 ,this accounts for the fact that our most indubitable and complete knowledge is concerning percepts1 not concerning other mental events or events in the external world4 ,our reaction to a sound can be to make a similar sound1 and if we are clever enough we can paint something very like what we see4 ,but we cannot show our knowledge of a pleasure by creating for ourselves another very similar pleasure1 nor of a desire by creating a similar desire4 ,thus percepts are known with more accuracy and certainty than anything else either in the outer world or in our own minds4 ,the conclusion we have reached in this chapter is that ,william ,james was right in his views on 8consciousness04 ,no mental occurrence has1 in its own intrinsic nature1 that sort of relational character that was implied in the opposition of subject and object1 or of knower and known4 ,nevertheless we can distinguish 8mental0 events from others1 and our most indubitable knowledge is concerned with a certain class of mental events4 ,we have arrived at this result by following out to its logical conclusion the behaviourist definition of knowledge which we gave in ,chapter ,,viii4 ,we have had to modify considerably the point of view which originally led us to that definition1 the modification having been forced upon us by the physical knowledge which1 starting from a common-sense realism1 has been gradually driven1 through the causal theory of perception1 to a view of cognition far more subjective than that from which physicists1 like the rest of mankind1 originally set out4 ,but ,i do not see how there can be any escape from this development4 ,,chapter ,,xxi ,,emotion1 ,,desire1 ,,and ,,will ,hitherto1 in our investigation of man from within1 we have considered only the cognitive aspect1 which is1 in fact1 the most important to philosophy4 ,but now we must turn our attention to the other sides of human nature4 ,if we treat them more briefly than the cognitive side1 it is not because they are less important1 but because their main importance is practical and our task is theoretical4 ,let us begin with the emotions4 ,the theory of the emotions has been radically transformed by the discovery of the part played by the ductless glands4 ,cannon's ,bodily ,changes in ,pain1 ,hunger1 ,fear and ,rage is a book whose teaching has come to be widely known1 though not more so than its importance warrants4 ,it appears that certain secretions from the glands into the blood are the essential physiological conditions of the emotions4 ,some people say that the physiological changes correlated with these secretions are the emotions4 ,i think this view must be received with some caution4 ,as everyone knows1 the adrenal glands secrete adrenin1 which produces the bodily symptoms of fear or rage4 ,on one occasion my dentist injected a considerable amount of this substance into my blood1 in the course of administering a local ansthetic4 ,i turned pale and trembled1 and my heart beat violently2 the bodily symptoms of fear were present1 as the books said they should be1 but it was quite obvious to me that ,i was not actually feeling fear4 ,i should have had the same bodily symptoms in the presence of a tyrant about to condemn me to death1 but there would have been something extra which was absent when ,i was in the dentist's chair4 ,what was different was the cognitive part3 ,i did not feel fear because ,i knew there was nothing to be afraid of4 ,in normal life1 the adrenal glands are stimulated by the perception of an object which is frightful or enraging2 thus there is already a cognitive element present4 ,the fear or rage attaches itself to the object which has stimulated the glands1 and the full emotion arises4 ,but when adrenin is artificially administered1 this cognitive element is absent1 and the emotion in its entirety fails to arise4 ,probably if it were administered in sleep it would produce a dream of terror1 in which the dreamer's imagination would supply an object for fear4 ,the same thing might happen on waking life with animals or young children4 ,but with an adult of average rationality1 the knowledge that there is nothing to be afraid of inhibits the full development of the emotion4 ,fear and rage are both active emotions1 demanding a certain kind of behaviour towards an object2 when this behaviour is obviously not called for1 it is impossible to feel either emotion fully4 ,there are1 however1 other emotions1 such as melancholy1 which do not demand an object4 ,these1 presumably1 can be caused in their entirety by administering the proper secretions4 ,a disordered liver may cause melancholy which is not relieved by knowledge of its source4 ,the emotions which do not require an object are those which do not call for any appropriate line of action4 ,emotions are subject to 8conditioning01 so that the stimuli which call them out become more various as a result of experience4 ,dr4 ,watson has found only two original stimuli to fear in young infants1 namely loud noises1 and lack of support2 but anything associated with either of these may become terrifying4 ,the separation of an emotional element in our integral reaction to a situation is more or less artificial4 ,no doubt there is a definite physiological concomitant1 namely stimulation of a gland2 but fear1 for example1 involves a mode of action towards an object1 for which mode of action the secretion of adrenin is helpful4 ,there is1 however1 something in common among a number of occasions that have a given emotional tone2 this may be seen from the fact that they are associated4 ,when we are feeling some emotion strongly1 we tend to think of other occasions when we have had similar feelings4 ,association by means of emotional similarity is a characteristic of a great deal of poetry4 ,and this accounts for the fact that1 if our blood is in a state usually associated with terror1 we shall1 if our critical faculty is in abeyance1 be very likely to imagine some cause of fear so vividly as to believe that it is really present3 ,in the night1 imagining some fear1 ,how easy is a bush supposed a bear4 ,but in a rational man1 if he is not drunk or sleepy1 other associations are too strong for this production of imaginary terrors4 ,that is why it is possible to show the physical symptoms of fear under the influence of adrenin1 without actually feeling the emotion4 ,the emotions are what makes life interesting1 and what makes us feel it important4 ,from this point of view1 they are the most valuable element in human existence4 ,but when1 as in philosophy1 we are trying to understand the world1 they appear rather as a hindrance4 ,they generate irrational opinions1 since emotional associations seldom correspond with collocations in the external world4 ,they cause us to view the universe in the mirror of our moods1 as now bright1 now dim1 according to the state of the mirror4 ,with the sole exception of curiosity1 the emotions are on the whole a hindrance to the intellectual life1 though the degree of vigour required for successful thinking is likely to be correlated with a considerable susceptibility to emotion4 ,if ,i say little about the emotions in this book1 it is not from under-estimating their human importance1 but solely because the task upon which we are engaged is theoretical rather than practical3 to understand the world1 not to change it4 ,and if emotion determines the ends we shall pursue1 knowledge is what gives us the power to realise them4 ,even from the practical point of view1 the advancement of knowledge is more useful than anything else that lies within human power4 ,i come now to the subject of desire1 which we considered from a behaviourist standpoint in ,chapter ,,iii4 ,i want now to ask whether there is anything to be added from an introspective point of view4 ,let us again remind ourselves that there is an element of artificiality in isolating elements within the one process leading from stimulus to reaction4 ,whenever a stimulus produces a reaction1 we may consider the reaction as the effect of the stimulus1 or as the cause of further effects4 ,the former is the natural way of viewing the reaction when we are concerned with knowledge2 the latter is the natural way when we are concerned with desire and will4 ,in desire1 we wish to change something in ourselves or in our environment or both4 ,the question is3 ,what can we discover introspectively about desire8 ,i think that here1 as in the case of knowledge1 the purely behaviouristic account is more important causally than the introspective account1 and applies over a much wider range4 ,desire as a characteristic of behaviour1 as considered in ,chapter ,,iii1 begins very low in the scale of evolution1 and remains1 even in human beings1 the whole of what can be discovered in a large number of instances4 ,the ,freudian 8unconscious0 desires give a formula which is useful as explaining causally a number of acts1 but these desires do not exist as anything except ways of behaving4 ,some desires1 on the other hand1 are conscious and explicit4 ,what1 exactly1 is added in these last that is not present in the others8 ,let us take some stock instance1 say1 ,demosthenes desiring to become a great orator4 ,this was a desire of which he was conscious1 and in accordance with which he deliberately moulded his actions4 ,one may suppose1 to begin with1 a merely behaviouristic tendency to do such things as seemed likely to impress his companions4 ,this is a practically universal characteristic of human nature1 which is displayed naively by children4 ,then come attempts1 just like those of rats in mazes1 to reach the goal2 wrong turnings1 leading to derision2 right turnings1 leading to a brief nibble at the cheese of admiration4 ,self-observation1 still of a behaviourist kind1 may lead to the formula3 ,i want to be admired4 ,at this point the desire has become 8conscious04 ,when this point has been reached1 knowledge can be brought to bear on the problem of achieving the desired end4 ,by association1 the means come to be desired also4 ,and so ,demosthenes arrives at the decision to subject himself to a difficult training as an orator1 since this seems the best way of achieving his end4 ,the whole development is closely analogous to that of explicit knowledge out of mere sensitivity2 it is1 indeed1 part of the very same evolution4 ,we cannot1 in our integral reaction to a situation1 separate out one event as knowledge and another as desire2 both knowledge and desire are features which characterise the reaction1 but do not exist in isolation4 ,in explicit conscious desire there is always an object1 just as there is in explicit conscious perception2 we desire some event or some state of affairs4 ,but in the primitive condition out of which explicit desire is evolved1 this is not the case4 ,we have a state of affairs which may be said to involve discomfort1 and activities of various sorts until a certain different state of affairs is achieved1 or fatigue supervenes1 or some other interest causes a distraction4 ,these activities will be such as to achieve the new state of affairs quickly if there has been previous experience of a relevant kind4 ,when we reach the level of explicit conscious desire1 it seems as if we were being attracted to a goal1 but we are really still pushed from behind4 ,the attraction to the goal is a shorthand way of describing the effects of learning together with the fact that our efforts will continue till the goal is achieved1 provided the time required is not too long4 ,there are feelings of various kinds connected with desire1 and in the case of familiar desires1 such as hunger1 these feelings become associated with what we know will cause the desire to cease4 ,but ,i see no more reason in the case of desire than in the case of knowledge to admit an essentially relational occurrence such as many suppose desire to be4 ,only experience1 memory and association--so ,i should say--confer objects upon desire1 which are initially blind tendencies to certain kinds of activity4 ,it remains to say a few words about 8will04 ,there is a sense in which will is an observable phenomena1 and another in which it is a metaphysical superstition4 ,it is obvious that ,i can say1 8,i will hold my breath for thirty seconds01 and proceed to do so2 that ,i can say1 8,i will go to ,america01 and proceed to do so2 and so on4 ,in this sense1 will is an observable phenomenon4 ,but as a faculty1 as a separable occurrence1 it is1 ,i think1 a delusion4 ,to make this clear1 it will be necessary to examine the observable phenomenon4 ,very young infants do not appear to have anything that could be called 8will04 ,their movements1 at first1 are reflexes1 and are explicable1 where they first cease to be reflexes1 by the law of conditioned reflexes4 ,one observes1 however1 something that looks very like will when the child learns control over fingers and toes4 ,it seems clear1 in watching this process1 that1 after some experience of involuntary movements1 the child discovers how to think of a movement first and then make the movement1 and that this discovery is exceedingly pleasurable4 ,we know that1 in adult life1 a deliberate movement is one which we think of before we make it4 ,obviously we cannot think of a movement unless we have previously made it2 it follows that no movement can be voluntary unless it has previously been involuntary4 ,i think that1 as ,william ,james suggested1 a voluntary movement is merely one which is preceded by the thought of it1 and has the thought of it as an essential part of its cause4 ,when ,i say this1 ,i do not mean to take any particular view as to what constitutes 8thinking04 ,it may consist almost entirely of talking1 as ,dr4 ,watson holds2 or it may be something more4 ,that is not the point at present4 ,the point is that1 whatever philosophy one may adopt1 there certainly is an occurrence which is described by ordinary people as 8thinking of getting up in the morning01 or 8thinking of0 any other bodily movement4 ,whatever the analysis of this occurrence may be1 it is an essential part of the cause of any movement which can be attributed to the 8will04 ,it is true1 of course1 that we may think of a movement without performing it4 ,this is analogous to imagining a state of affairs without believing in it2 each is a rather sophisticated and late development4 ,each will only happen when we think of several things at once1 and one of them interferes with another4 ,it may1 ,i think1 be assumed that1 whenever we think of a possible movement1 we have a tendency to perform it1 and are only restrained1 if at all1 by some thought1 or other circumstance1 having a contrary tendency4 ,if this is the case1 there is nothing at all mysterious about the will4 ,whatever may constitute 8thinking of0 a movement1 it is certainly something associated with the movement itself2 therefore1 by the usual law of learned reactions we should expect that thinking of a movement would tend to cause it to occur4 ,this1 ,i should say1 is the essence of will4 ,emphatic cases of volition1 where we decide after a period of deliberation1 are merely examples of conflicting forces4 ,you may have both pleasant and unpleasant associations with some place that you are thinking of going to2 this may cause you to hesitate1 until one or other association proves the stronger4 ,there may be more than this in volition1 but ,i cannot see any good ground for believing that there is4 ,,chapter ,,xxii ,,ethics ,ethics is traditionally a department of philosophy1 and that is my reason for discussing it4 ,i hardly think myself that it ought to be included in the domain of philosophy1 but to prove this would take as long as to discuss the subject itself1 and would be less interesting4 ,as a provisional definition1 we may take ethics to consist of general principles which help to determine rules of conduct4 ,it is not the business of ethics to say how a person should act in such and such specific circumstances2 that is the province of casuistry4 ,the word 8casuistry0 has acquired bad connotations1 as a result of the ,protestant and ,jansenist attacks on the ,jesuits4 ,but in its old and proper sense it represents a perfectly legitimate study4 ,take1 say1 the question3 ,in what circumstances is it right to tell a lie8 ,some people1 unthinkingly1 would say3 ,never6 ,but this answer cannot be seriously defended4 ,everybody admits that you should lie if you meet a homicidal maniac pursuing a man with a view to murdering him1 and he asks you whether the man has passed your way4 ,it is admitted that lying is a legitimate branch of the art of warfare2 also that priests may lie to guard the secrets of the confessional1 and doctors to protect the professional confidences of their patients4 ,all such questions belong to casuistry in the old sense1 and it is evident that they are questions deserving to be asked and answered4 ,but they do not belong to ethics in the sense in which this study has been included in philosophy4 ,it is not the business of ethics to arrive at actual rules of conduct1 such as3 8,thou shalt not steal04 ,this is the province of morals4 ,ethics is expected to provide a basis from which such rules can be deduced4 ,the rules of morals differ according to the age1 the race1 and the creed of the community concerned1 to an extent that is hardly realised by those who have neither travelled nor studied anthropology4 ,even within a homogeneous community differences of opinion arise4 ,should a man kill his wife's lover8 ,the ,church says no1 the law says no1 and common sense says no2 yet many people would say yes1 and juries often refuse to condemn4 ,these doubtful cases arise when a moral rule is in process of changing4 ,but ethics is concerned with something more general than moral rules1 and less subject to change4 ,it is true that1 in a given community1 an ethic which does not lead to the moral rules accepted by that community is considered immoral4 ,it does not1 of course1 follow that such an ethic is in fact false1 since the moral rules of that community may be undesirable4 ,some tribes of head-hunters hold that no man should marry until he can bring to the wedding the head of an enemy slain by himself4 ,those who question this moral rule are held to be encouraging licence and lowering the standard of manliness4 ,nevertheless1 we should not demand of an ethic that it should justify the moral rules of head-hunters4 ,perhaps the best way to approach the subject of ethics is to ask what is meant when a person says3 8,you ought to do so-and-so0 or 8,i ought to do so-and-so04 ,primarily1 a sentence of this sort has an emotional content2 it means 8this is the act towards which ,i feel the emotion of approval04 ,but we do not wish to leave the matter there2 we want to find something more objective and systematic and constant than a personal emotion4 ,the ethical teacher says3 8,you ought to approve acts of such-and-such kinds04 ,he generally gives reasons for this view1 and we have to examine what sorts of reasons are possible4 ,we are here on very ancient ground4 ,socrates was concerned mainly with ethics2 ,plato and ,aristotle both discussed the subject at length2 before their time1 ,confucius and ,buddha had each founded a religion consisting almost entirely of ethical teaching1 though in the case of ,buddhism there was afterwards a growth of theological doctrine4 ,the views of the ancients on ethics are better worth studying than their views on 7say7 physical science2 the subject has not yet proved amenable to exact reasoning1 and we cannot boast that the moderns have as yet rendered their predecessors obsolete4 ,historically1 virtue consisted at first of obedience to authority1 whether that of the gods1 the government1 or custom4 ,those who disobeyed authority suffered obvious penalties4 ,this is still the view of ,hegel1 to whom virtue consists in obedience to the ,state4 ,there are1 however1 different forms of this theory1 and the objections to them are different4 ,in its more primitive form1 the theory is unaware that different authorities take different views as to what constitutes virtue1 and it therefore universalises the practice of the community in which the theoriser lives4 ,when other ages and nations are found to have different customs1 these are condemned as abominations4 ,let us consider this view first4 ,the view we are now to examine is the theory that there are certain rules of conduct--e4g4 the ,decalogue--which determine virtue in all situations4 ,the person who keeps all the rules is perfectly virtuous2 the person who fails in this is wicked in proportion to the frequency of his failures4 ,there are several objections to this as the basis of ethics4 ,in the first place1 the rules can hardly cover the whole field of human conduct2 e4g4 there is nothing in the ,decalogue to show whether we ought to have a gold standard or not4 ,accordingly those who hold this view regard some questions as 8moral issues01 while others have not this character4 ,that means1 in practice1 that in regard to 8moral issues0 we ought to act in a certain way1 regardless of consequences1 while in other matters we ought to consider which course will do the most good4 ,thus in effect we are driven to adopt two different ethical systems1 one where the code has spoken1 the other where it is silent4 ,this is unsatisfactory to a philosopher4 ,the second objection to such a view is suggested by the first4 ,we all feel that certain results are desirable1 and others undesirable2 but a code of conduct which takes no account of circumstances will have sometimes the sort of consequences we think desirable1 and sometimes the sort we think undesirable4 ,take1 e4g4 the precept 8,thou shalt not kill04 ,all respectable people hold that this does not apply when the ,state orders a person to kill2 on this ground among others1 the ,new ,york ,school ,board recently refused to sanction the teaching of the ,decalogue in schools4 ,a third objection is that it may be asked how the moral rules are known4 ,the usual answer1 historically1 is that they are known by revelation and tradition4 ,but these are extra-philosophical sources of knowledge4 ,the philosopher cannot but observe that there have been many revelations1 and that it is not clear why he should adopt one rather than another4 ,to this it may be replied that conscience is a personal revelation to each individual1 and invariably tells him what is right and what is wrong4 ,the difficulty of this view is that conscience changes from age to age4 ,most people nowadays consider it wrong to burn a man alive for disagreeing with them in metaphysics1 but formerly this was held to be a highly meritorious act1 provided it was done in the interests of the right metaphysics4 ,no one who has studied the history of moral ideas can regard conscience as invariably right4 ,thus we are driven to abandon the attempt to define virtue by means of a set of rules of conduct4 ,there is1 however1 another form of the view that virtue consists in obedience to authority4 ,this may be called 8the administrator's ethic04 ,a ,roman or ,anglo-,indian pro-consul would define virtue as obedience to the moral code of the community to which a man happens to belong4 ,no matter how moral codes may differ1 a man should always obey that of his own time and place and creed4 ,a ,mohammedan1 for instance1 would not be regarded as wicked for practising polygamy1 but an ,englishman would1 even if he lived in a ,mohammedan country4 ,this view makes social conformity the essence of virtue2 or1 as with ,hegel1 regards virtue as obedience to the government4 ,the difficulty of such theories is that they make it impossible to apply ethical predicates to authority3 we cannot find any meaning for the statement that a custom is good or that the government is bad4 ,the view is appropriate to despots and their willing slaves2 it cannot survive in a progressive democracy4 ,we come a little nearer to a correct view when we define right conduct by the motive or state of mind of the agent4 ,according to this theory1 acts inspired by certain emotions are good1 and those inspired by certain other emotions are bad4 ,mystics hold this view1 and have accordingly a certain contempt for the letter of the law4 ,broadly speaking1 it would be held that acts inspired by love are good1 and those inspired by hate are bad4 ,in practice1 ,i hold this view to be right2 but philosophically ,i regard it as deducible from something more fundamental4 ,all the theories we have hitherto considered are opposed to those which judge the rightness or wrongness of conduct by its consequences4 ,of these the most famous is the utilitarian philosophy1 which maintained that happiness is the good1 and that we ought to act so as to maximise the balance of happiness over unhappiness in the world4 ,i should not myself regard happiness as an adequate definition of the good1 but ,i should agree that conduct ought to be judged by its consequences4 ,i do not mean1 of course1 that in every practical exigency of daily life we should attempt to think out the results of this or that line of conduct1 because1 if we did1 the opportunity for action would often be past before our calculations were finished4 ,but ,i do mean that the received moral code1 in so far as it is taught in education and embodied in public opinion or the criminal law1 should be carefully examined in each generation1 to see whether it still serves to achieve desirable ends1 and1 if not1 in what respects it needs to be amended4 ,the moral code1 in short1 like the legal code1 should adapt itself to changing circumstances1 keeping the public good always as its motive4 ,if so1 we have to consider in what the public good consists4 ,according to this view1 8right conduct0 is not an autonomous concept1 but means 8conduct calculated to produce desirable results04 ,it will be right1 let us say1 to act so as to make people happy and intelligent1 but wrong to act so as to make them unhappy and stupid4 ,we have to ask ourselves how we can discover what constitutes the ends of right conduct4 ,there is a view1 advocated1 e4g4 by ,dr4 ,g4 ,e4 ,moore1 that 8good0 is an indefinable notion1 and that we know a priori certain general propositions about the kinds of things that are good on their own account4 ,such things as happiness1 knowledge1 appreciation of beauty1 are known to be good1 according to ,dr4 ,moore2 it is also known that we ought to act so as to create what is good and prevent what is bad4 ,i formerly held this view myself1 but ,i was led to abandon it1 partly by ,mr4 ,santayana's ,winds of ,doctrine4 ,i now think that good and bad are derivative from desire4 ,i do not mean quite simply that the good is the desired1 because men's desires conflict1 and 8good0 is1 to my mind1 mainly a social concept1 designed to find an issue from this conflict4 ,the conflict1 however1 is not only between the desires of different men1 but between incompatible desires of one man at different times1 or even at the same time1 and even if he is solitary1 like ,robinson ,crusoe4 ,let us see how the concept of 8good0 emerges from reflection or conflicts of desires4 ,we will begin with ,robinson ,crusoe4 ,in him there will be conflicts1 for example1 between fatigue and hunger1 particularly between fatigue at one time and foreseen hunger at another4 ,the effort which he will require in order to work when he is tired with a view to providing food on another occasion has all the characteristics of what is called a moral effort3 we think better of a man who makes the effort than of one who does not1 and the making of it requires self-control4 ,for some reason1 this sort of thing is called1 not morals1 but 8morale02 the distinction1 however1 seems to me illusory4 ,robinson ,crusoe is bound to realise that he has many desires1 each of which is stronger at one time than at another1 and that1 if he acts always upon the one that is strongest at the moment1 he may defeat others that are stronger in the long run4 ,so far1 only intelligence is involved2 but one may assume that1 with the progress of intelligence1 there goes a growing desire for a harmonious life1 i4e4 a life in which action is dominated by consistent quasi-permanent desires4 ,again3 some desires1 in addition to the desire for a harmonious life1 are more likely to lead to harmony then certain other desires4 ,intellectual curiosity1 e4g4 affords a mild diffused satisfaction1 whereas drugs provide ecstasy followed by despair4 ,if we arrive unexpectedly in ,robinson ,crusoe's island and find him studying botany1 we shall think better of him than if we find him dead drunk on his last bottle of whisky4 ,all this belongs to morals1 although it is purely self-regarding4 ,when we come to considering men in society1 moral questions become both more important and more difficult1 because conflicts between the desires of different persons are harder to resolve than internal conflicts among the desires of one person4 ,there are some distinctions to be made4 ,first1 there is the difference between the point of view of the neutral authority contemplating a squabble in which it is not interested1 and the point of view of the disputants themselves4 ,then there is the distinction between what we wish people to do1 and what we wish them to feel in the way of emotions and desires4 ,the view of authority everywhere is that squabbles to which it is not a party are undesirable1 but that in the squabbles to which it is a party virtue consists in promoting the victory of authority4 ,in the latter respect1 it is acting1 not as an authority1 but merely as a combination of quarrelsome individuals who think it more profitable to quarrel with outsiders than with each other2 we will therefore ignore this aspect of authority1 and consider its action only when it is a neutral4 ,in this case1 it aims at preventing quarrels by punishing those who begin them1 or sometimes by punishing both parties4 ,monsieur ,huc1 the ,jesuit missionary who wrote a fascinating account of his travels in ,china1 ,tartary1 and ,tibet about eighty years ago1 relates an amusing conversation he had with a mandarin4 ,monsieur ,huc had remarked that ,chinese justice was dilatory1 expensive1 and corrupt4 ,the mandarin explained that it had been made so in obedience to an ,imperial edict1 setting forth that the subjects of the ,son of ,heaven had become too much addicted to litigation1 and must be led to abandon this practice4 ,the rescript then proceeded to suggest to magistrates and judges the desirability of the above defects as a means of diminishing the number of law-suits4 ,it appeared that the ,emperor's commands had been faithfully obeyed in this respect--more so than in some others4 ,another method adopted by public authorities to prevent the impulse towards internal quarrels is the creation of esprit de corps1 public spirit1 patriotism1 etc41 i4e4 a concentration of quarrelsome impulses or persons outside the group over which it rules4 ,such a method1 obviously1 is partial and external2 it would not be open to a world-wide democratic authority1 should this ever come into existence4 ,such an authority would have to adopt better methods of producing harmony2 it would also have a higher claim to the obedience of citizens than some authorities have at present4 ,what can we say from the point of view of the disputants themselves8 ,it is of course obvious that there will be a greater total satisfaction when two people's desires harmonise than when they conflict1 but that is not an argument which can be used to people who in fact hate each other4 ,one can argue that the one who is going to be beaten would do well to give way1 but each will think that he himself is going to be victorious4 ,one can argue that there is more happiness to be derived from love than from hate1 but people cannot love to order1 and there is no satisfaction to be derived from an insincere love4 ,nor is it always true in an individual case that love brings more happiness than hate4 ,during and immediately after the war1 those who hated the ,germans were happier than those who still regarded them as human beings1 because they could feel that what was being done served a good purpose4 ,i think1 therefore1 that certain departments of morals1 and those the most important1 cannot be inculcated from a personal point of view1 but only from the point of view of a neutral authority4 ,that is why ,i said that ethics is mainly social4 ,the attitude of a neutral authority would1 it seems to me1 be this3 ,men desire all sorts of things1 and in themselves all desires1 taken singly1 are on a level1 i4e4 there is no reason to prefer the satisfaction of one to the satisfaction of another4 ,but when we consider not a single desire but a group of desires1 there is this difference1 that sometimes all the desires in a group can be satisfied1 whereas in other cases the satisfaction of some of the desires in the group is incompatible with that of others4 ,if ,a and ,b desire to marry each other1 both can have what they want1 but if they desire to kill each other1 at most one can succeed1 unless they are ,kilkenny cats4 ,therefore the former pair of desires is socially preferable to the latter4 ,now our desires are a product of three factors3 native disposition1 education1 and present circumstances4 ,the first factor is difficult to deal with at present1 for lack of knowledge4 ,the third is brought into operation by means of the criminal law1 economic motives1 and social praise and blame1 which make it on the whole to the interest of an individual in a community to promote the interests of the dominant group in that community4 ,but this is done in an external way1 not by creating good desires1 but by producing a conflict of greed and fear in which it is hoped that fear will win4 ,the really vital method is education1 in the large sense in which it includes care of the body and habit-formation in the first few years4 ,by means of education1 men's desires can be changed1 so that they act spontaneously in a social fashion4 ,to force a man to curb his desires1 as we do by the criminal law1 is not nearly so satisfactory as to cause him genuinely to feel the desires which promote socially harmonious conduct4 ,and this brings me to the last point with which we are concerned1 namely1 the distinction between feeling and doing4 ,no doubt1 from a social point of view the important thing is what a man does1 but it is impossible to cause a man to do the right things consistently unless he has the right desires4 ,and the right desires cannot be produced merely by praising them or by desiring to have them2 the technique of moral education is not one of exhortation or explicit moral instruction4 ,we can now state the ethic at which we have arrived in abstract terms4 ,primarily1 we call something 8good0 when we desire it1 and 8bad0 when we have an aversion from it4 ,but our use of words is more constant than our desires1 and therefore we shall continue to call a thing good even at moments when we are not actually desiring it1 just as we always call grass green though it sometimes looks yellow4 ,and the laudatory associations of the word 8good0 may generate a desire which would not otherwise exist3 we may want to eat caviare merely because we are told that it is good4 ,moreover the use of words is social1 and therefore we learn only to call a thing good1 except in rare circumstances1 if most of the people we associate with are also willing to call it good4 ,thus 8good0 comes to apply to things desired by the whole of a social group4 ,it is evident1 therefore1 that there can be more good in a world where the desires of different individuals harmonise than in one where they conflict4 ,the supreme moral rule should1 therefore1 be3 ,act so as to produce harmonious rather than discordant desires4 ,this rule will apply wherever a man's influence extends3 within himself1 in his family1 his city1 his country1 even the world as a whole1 if he is able to influence it4 ,there will be two main methods to this end3 first1 to produce social institutions under which the interests of different individuals or groups conflict as little as possible2 second1 to educate individuals in such a way that their desires can be harmonised with each other and with the desires of their neighbours4 ,as to the first method1 ,i shall say nothing further1 since the questions that arise belong to politics and economics4 ,as to the second1 the important period is the formative period of childhood1 during which there should be health1 happiness1 freedom1 and a gradual growth of self-discipline through opportunities for difficult achievement of a sort which is useful and yet satisfies the impulse towards mastery of the environment4 ,the desire for power1 which is present in most people and strongest in the most vigorous1 should be directed towards power over things rather than over people4 ,it is clear that1 if harmonious desires are what we should seek1 love is better than hate1 since1 when two people love each other1 both can be satisfied1 whereas when they hate each other one at most can achieve the object of his desire4 ,it is obvious also that desire for knowledge is to be encouraged1 since the knowledge that a man acquires is not obtained by taking it away from some one else2 but a desire for 7say7 large landed estates can only be satisfied in a small minority4 ,desire for power over other people is a potent source of conflict1 and is therefore to be discouraged2 a respect for the liberty of others is one of the things that ought to be developed by the right kind of education4 ,the impulse towards personal achievement ought to go into such things as artistic creation or scientific discovery or the promotion of useful institutions--in a word1 into activities that are creative rather than possessive4 ,knowledge1 which may do positive harm where men's desires conflict 7for example1 by showing how to make war more deadly71 will have only good results in a world where men's desires harmonise1 since it tends to show how their common desires are to be realised4 ,the conclusion may be summed up in a single phrase3 ,the good life is one inspired by love and guided by knowledge4#aa #aa ,cf4 ,what ,i ,believe1 by the present author--,to-day and ,to-morrow ,series4 ,,part ,,iv ,,the ,,universe ,,chapter ,,xxiii ,,some ,,great ,,philosophies ,,of ,,the ,,past ,our discussions1 hitherto1 have been concerned very largely with ,man1 but ,man on his own account is not the true subject-matter of philosophy4 ,what concerns philosophy is the universe as a whole2 ,man demands consideration solely as the instrument by means of which we acquire knowledge of the universe4 ,and that is why it is human beings as capable of knowledge that have concerned us mainly in past chapters1 rather than as centres of will or of emotion4 ,we are not in the mood proper to philosophy so long as we are interested in the world only as it affects human beings2 the philosophic spirit demands an interest in the world for its own sake4 ,but since we apprehend the world through our own senses1 and think about it with our own intellect1 the picture that we acquire is inevitably coloured by the personal medium through which it comes to us4 ,consequently we have to study this medium1 namely ourselves1 in order to find out1 if we can1 what elements in our picture of the world are contributed by us1 and what elements we may accept as representative of outside fact4 ,previous chapters have studied cognition1 both as an outwardly observable reaction1 and as it appears to introspection4 ,in the chapters that remain1 we shall be concerned with what we can know about the universe1 in view of the nature of the instrument that we have to employ4 ,i do not think we can know as much as many philosophers of the past have supposed1 but ,i think it is worth while to have in our minds an outline of their systems4 ,i shall therefore begin by setting forth a few typical philosophical constructions of earlier centuries4 ,modern philosophy is generally taken as beginning with ,descartes1 who flourished in the first half of the seventeenth century4 ,we have already had occasion1 in ,chapter ,,xvi1 to consider his argument 8,i think1 therefore1 ,i am01 but now we will deal with him somewhat more generally4 ,he inaugurated two movements1 one in metaphysics1 one in theory of knowledge4 ,in metaphysics1 he emphasised the gulf between mind and matter1 or between soul and body2 in theory of knowledge he advocated a critical scrutiny of premises4 ,these two movements had different histories1 each of them interesting4 ,the science of dynamics was rapidly developing in ,descartes' time1 and seemed to show that the motions of matter could be calculated mathematically1 given sufficient data4 ,as the motions of matter include our bodily acts1 even speaking and writing1 it seemed as if the consequence must be a materialistic theory of human behaviour4 ,this consequence1 however1 was distasteful to most philosophers1 and they therefore invented various ways of escaping from it4 ,descartes himself thought that the will could have certain direct physical effects4 ,he thought that the brain contains a fluid called the 8animal spirits01 and that the will could influence the direction of its motion1 though not the velocity4 ,in this way he was still able to hold that the will is effective in the manner in which common sense supposes it to be4 ,but this view did not fit in at all well with the rest of his philosophy4 ,he held that1 apart from the ,supreme ,substance1 namely ,god1 there are two created substances1 mind and matter2 that the essence of mind is thought1 and that the essence of matter is extension4 ,he made these two substances so different that interaction between them became difficult to understand1 and his followers decided that there is never any effect either of mind on matter or of matter on mind4 ,the motives for this development were various2 perhaps the most important was the development of physics immediately after ,descartes' time4 ,a law was discovered called the 8conservation of momentum04 ,this states that1 if a system of bodies is in any sort of motion1 and is free from outside influences1 the amount of motion in any direction is constant4 ,this showed that the kind of action of the will on the 8animal spirits0 which ,descartes had assumed was contrary to the principles of dynamics4 ,it seemed to follow that mind cannot influence matter1 and it was inferred that matter cannot influence mind1 since the two were regarded as co-equal substances4 ,it was held that each goes it own way1 according to its own laws4 ,the fact that our arm moves when we will it to move was regarded as analogous to the fact that two perfectly accurate clocks strike at the same moment1 though neither has any effect upon the other4 ,the series of mental events and the series of physical events were parallel1 each going at the same rate as the other1 therefore they continued to synchronise1 in spite of their independence of each other4 ,spinoza sought to make this parallelism less mysterious by denying that there are two separate substances1 mind and matter4 ,he maintained that there is only one substance1 of which thought and extension are attributes4 ,but there seemed still no good reason why the events belonging to the two attributes should develop along parallel lines4 ,spinoza is in many ways one of the greatest philosophers1 but his greatness is rather ethical than metaphysical4 ,accordingly he was regarded by contemporaries as a profound metaphysician but a very wicked man4 ,the notion of the impossibility of interaction between mind and body has persisted down to our own day4 ,one still hears of 8psychophysical parallelism01 according to which to every state of the brain a state of mind corresponds and vice versa1 without either acting on the other4 ,this whole point of view1 though not exactly that of ,descartes1 derives from him4 ,it has a number of sources1 religious1 metaphysical1 and scientific2 but there seems no ground whatever for regarding it as true4 ,take1 first1 the rigid determinism of traditional physics1 which was to have been avoided4 ,spinoza rightly perceived that this could not be avoided by such methods1 and therefore accepted determinism in the psychical as in the physical realm4 ,if everything we say is determined by physical causes1 our thoughts are only free when we tell lies3 so long as we say what we think1 our thoughts also can be inferred from physics4 ,the philosophy which ,i advocate escapes this consequence in several ways4 ,in the first place1 causality does not involve compulsion1 but only a law of sequence3 if physical and mental events run parallel1 either may with equal justice be regarded as causing the other1 and there is no sense in speaking of them as causally independent4 ,thus the ,cartesian dualism does not have the pleasant consequences which were intended4 ,in the second place1 modern physics has become less deterministic than the physics of the past few centuries4 ,we do not know1 e4g4 what makes a radio-active atom explode or an electron jump from a larger to a smaller orbit4 ,in these matters we only know statistical averages4 ,take next the view that mind and matter are quite disparate4 ,this we have criticised already4 ,it rests upon a notion that we know much more about matter than we do1 and in particular upon the belief that the space of physics can be identified with the space of sensible experience4 ,this belief is absent in ,leibniz1 who1 however1 never quite realised what his own view was4 ,it is not absent in ,kant1 who realised that the space of sensible experience is subjective1 and inferred that the space of physics is subjective4 ,since ,kant1 no one seems to have thought clearly about space until ,einstein and ,minkowski4 ,the separation of physical and sensible space1 logically carried out1 shows the groundlessness of traditional views about mind and matter4 ,this part of ,descartes' philosophy1 therefore1 though it accelerated the progress of physics1 must be regarded as metaphysically an aberration4 ,the other part of ,descartes' philosophy1 namely1 the emphasis upon methodical doubt1 and consequently upon theory of knowledge1 has been more fruitful4 ,the beginning of a philosophic attitude is the realisation that we do not know as much as we think we do1 and to this ,descartes contributed notably4 ,we have seen that he set to work to doubt all he could1 but found he could not doubt his own existence1 which he therefore took as the starting-point of his constructive system4 ,he supposed that the most certain fact in the world is 8,i think04 ,this was unfortunate1 since it gave a subjective bias to modern philosophy4 ,as a matter of fact1 8,i0 seems to be only a string of events1 each of which separately is more certain than the whole4 ,and 8think0 is a word which ,descartes accepted as indefinable1 but which really covers complicated relations between events4 ,when is an event a 8thought08 ,is there some intrinsic characteristic which makes it a thought8 ,descartes would say yes1 and so would most philosophers4 ,i should say no4 ,take1 e4g4 a visual and an auditory sensation4 ,both are 8thoughts0 in ,descartes' sense1 but what have they in common8 ,two visual sensations have an indefinable common quality1 viz4 that which makes them visual4 ,two auditory sensations likewise4 ,but a visual and an auditory sensation have in common1 if ,i am not mistaken1 no intrinsic property1 but a certain capacity for being known without inference4 ,this amounts to saying that they are mnemic causes of a certain kind of event1 called a cognition1 and that they have moreover1 a certain formal similarity to the cognition which they cause4 ,therefore1 instead of taking the general 8,i think0 as our basis1 we ought to take the particular occurrences which are known without inference1 among which sensations 7or rather 8perceptions07 will be included4 ,these occurrences1 as we have already seen1 may be regarded with equal justice as physical and mental3 they are parts of chains of physical causation1 and they have mnemic effects which are cognitions4 ,the former fact makes us call them physical1 the latter mental1 both quite truly4 ,it is the particular events which are certain1 not the 8,i think0 which ,descartes made the basis of his philosophy4 ,it is not correct to regard the ultimate certainties as 8subjective01 except in the sense that they are events in that part of space-time in which our body is--and our mind also1 ,i should say4 ,a new turn was given to the ,cartesian type of metaphysics by ,leibniz 7#afdf-agaf71 who1 like ,descartes1 was supremely eminent both in mathematics and in philosophy4 ,leibniz rejected the view that there is only one substance1 as ,spinoza held1 or only two other than ,god1 as the orthodox followers of ,descartes maintained4 ,he also rejected the dualism of mind and matter1 holding that there are innumerable substances all in a greater or less degree mental1 and none in any degree material4 ,he maintained that every substance is immortal1 and that there is no interaction between one substance and another--this last being a view derived from the ,cartesian independence of mind and matter4 ,he also extended to his many substances the belief in parallelism which had existed for the two substances of the ,cartesians4 ,he called his substances 8monads01 and maintained that every monad mirrors the universe1 and develops along lines which correspond1 point by point1 with those along which every other monad is developing4 ,a man's soul or mind is a single monad1 while his body is a collection of monads1 each mental in some degree1 but less so than the monad which is his soul4 ,inferior monads mirror the world in a more confused way than higher ones do1 but there is some element of confusion in the perceptions of even the most superior monads4 ,every monad mirrors the world from its own point of view1 and the difference between points of view is compared to a difference of perspective4 8,matter0 is a confused way of perceiving a number of monads2 if we perceived clearly1 we should see that there is no such thing as matter4 ,leibniz's system had great merits and great demerits4 ,the theory that 8matter0 is a confused way of perceiving something non-material was an advance upon anything to be found in his predecessors4 ,he had1 though only semi-consciously1 the distinction between physical and perceptual space3 there is space in each monad's picture of the world1 and there is also the assemblage or pattern of 8points of view04 ,the latter corresponds to what ,i have called 8physical space01 the former to 8perceptual space04 ,leibniz maintained1 as against ,newton1 that space and time consists only of relations--a view which has achieved a definitive triumph in ,einstein's theory of relativity4 ,the weak point of his system was what he called the 8pre-established harmony01 in virtue of which all the monads 7so to speak7 kept step1 in spite of the fact that they were 8windowless0 and never acted upon each other4 ,perception1 for ,leibniz1 was not an effect of the object perceived1 but a modification arising in the perceiving monad and running parallel with what was happening in the perceived object4 ,this view would never have seemed plausible but for the anterior ,cartesian theory of the mutual independence of mind and matter4 ,and if ,leibniz himself developed1 as he believed1 in complete independence of all other created things1 it is not clear what good reasons he could have had for believing in the existence of anything except himself1 since1 by his own theory1 his experiences would remain unchanged if everything else were annihilated4 ,in fact1 he was only able to refute this possibility by bringing in theological considerations1 which1 whether valid or not1 are out of place in philosophy4 ,for this reason1 his doctrines1 ingenious as they were1 found little acceptance in ,france and ,england1 though in ,germany they prevailed1 in a modified form1 until the time of ,kant4 ,the systems of ,descartes1 ,spinoza and ,leibniz have one very important characteristic in common1 namely1 that they all depend upon the category of 8substance04 ,this is a concept which has developed out of the common-sense notion of 8thing04 ,a 8substance0 is that which has qualities1 and is in general supposed to be indestructible1 though it is difficult to see why4 ,it acquired its hold over metaphysicians partly because both matter and the soul were held to be immortal1 and partly through a hasty transference to reality of ideas derived from grammar4 ,we say 8,peter is running01 8,peter is talking01 8,peter is eating01 and so on4 ,we think that there is one entity1 ,peter1 who does all these things1 and that none of them could be done unless there were someone to do them1 but that ,peter might quite well do none of them4 ,similarly we assign qualities to ,peter3 we say he is wise and tall and blond and so on4 ,all these qualities1 we feel1 cannot subsist by themselves in the void1 but only when there is a subject to which they belong2 but ,peter would remain ,peter even if he became foolish and short and dyed his hair4 ,thus ,peter1 who is regarded as a 8substance01 is self-subsistent as compared with his qualities and states1 and he preserves his substantial identity throughout all sorts of changes4 ,similarly in the material world an atom is supposed 7or rather was supposed until recently7 to preserve its identity throughout all time1 however it might move and whatever combinations it might form with other atoms4 ,the concept of 8motion01 upon which all physics seemed to depend1 was only strictly applicable to a substance which preserves its identity while changing its spatial relations to other substances2 thus 8substance0 acquired an even firmer hold upon physics than upon metaphysics4 ,nevertheless1 the notion of 8substance01 at any rate in any sense involving permanence1 must be shut out from our thoughts if we are to achieve a philosophy in any way adequate either to modern physics or to modern psychology4 ,modern physics1 both in the theory of relativity and in the ,heisenberg-,schrdinger theories of atomic structure1 has reduced 8matter0 to a system of events1 each of which lasts only for a very short time4 ,to treat an electron or a proton as a single entity has become as wrong-headed as it would be to treat the population of ,london or ,new ,york as a single entity4 ,and in psychology1 equally1 the 8ego0 has disappeared as an ultimate conception1 and the unity of a personality has become a peculiar causal nexus among a series of events4 ,in this respect1 grammar and ordinary language have been shown to be bad guides to metaphysics4 ,a great book might be written showing the influence of syntax on philosophy2 in such a book1 the author could trace in detail the influence of the subject-predicate structure of sentences upon ,european thought1 more particularly in this matter of 8substance04 ,and it must be understood that the same reasons which lead to the rejection of substance lead also to the rejection of 8things0 and 8persons0 as ultimately valid concepts4 ,i say 8,i sit at my table01 but ,i ought to say3 8,one of a certain string of events causally connected in the sort of way that makes the whole series that is called a #8person' has a certain spatial relation to one of another string of events causally connected with each other in a different way and having a spatial configuration of the sort denoted by the word #8table'04 ,i do not say so1 because life is too short2 but that is what ,i should say if ,i were a true philosopher4 ,apart from any other grounds1 the inadequacy of the notion of 8substance0 would lead us to regard the philosophy of ,descartes1 ,spinoza1 and ,leibniz as incompatible with modern science4 ,there is of course in all three1 a great deal that does not depend upon 8substance01 and that still has value2 but 8substance0 supplied the framework and a good deal of the argumentation1 and therefore introduces a fatal defect into these three great systems4 ,i come now to the triad of ,british philosophers1 ,locke1 ,berkeley1 and ,hume--,english1 ,irish1 and ,scotch respectively4 ,perhaps from patriotic bias or from community of national temperament1 ,i find more that ,i can accept1 and regard as still important1 in the writings of these three than in the philosophy of their continental predecessors4 ,their constructions are less ambitious1 their arguments more detailed1 and their methods more empirical2 in all these respects they show more kinship with the modern scientific outlook4 ,on the other hand1 ,locke and ,hume1 if not ,berkeley1 approach philosophy too exclusively from the side of psychology1 and are concerned to study ,man rather than the universe4 ,locke was a contemporary and friend of ,newton2 his great book1 ,an ,essay concerning ,human ,understanding1 was published at almost the same moment as ,newton's ,principia4 ,his influence has been enormous1 greater1 in fact1 than his abilities would seem to warrant2 and this influence was not only philosophical1 but quite as much political and social4 ,he was one of the creators of eighteenth century liberalism3 democracy1 religious toleration1 freedom of economic enterprise1 educational progress1 all owe much to him4 ,the ,english ,revolution of #afhh embodied his ideas2 the ,american ,revolution of #aggf and the ,french ,revolution of #aghi expressed what had grown1 in a century1 out of his teaching4 ,and in all these movements1 philosophy and politics went hand in hand4 ,thus the practical success of ,locke's ideas has been extraordinary4 ,when1 knowing all this1 one comes to read ,locke himself1 it is difficult to resist a feeling of disappointment4 ,he is sensible1 enlightened1 minute1 but uninspired and 7to moderns7 uninspiring4 ,one has to remember that his contemporaries found common sense exhilarating after a century of wars of religion and a long struggle with obscurantism4 ,locke combatted the doctrine of 8innate ideas01 according to which we learned only certain things by experience1 but possessed our abstract knowledge in virtue of our congenital constitution4 ,he regarded the mind at birth as a wax tablet1 upon which experience proceeded to write4 ,undoubtedly he was1 in this matter1 more in the right than his opponents1 although the terms in which the controversy was waged are not such as a modern could employ4 ,we should say that the innate apparatus of man consists of 8reflexes0 rather than 8ideas02 also that our sense-organs1 our glands1 and our muscles lead to responses of certain kinds1 in which our own organisation plays a part of the same importance as that played by the external stimulus4 ,the element in our knowledge-responses that corresponds to our own bodily organisation might1 perhaps1 be regarded as representing what ,locke's opponents meant by 8innate04 ,but it does not represent this at all accurately so far as our feelings towards it are concerned4 ,the 8innate0 ideas were the ideas to be proud of2 they embraced pure mathematics1 natural theology1 and ethics4 ,but nobody is proud of sneezing or coughing4 ,and when ,locke tried to show1 in detail1 how our knowledge is generated by experience1 he was liberating philosophy from a great deal of useless lumber1 even if his own doctrines were not altogether such as we can now accept4 ,locke used his own principles only in ways consistent with common sense2 ,berkeley and ,hume both pushed them to paradoxical conclusions4 ,the philosophy of ,berkeley1 to my mind1 has not received quite the attention and respect that it deserves--not that ,i agree with it1 but that ,i think it ingenious and harder to refute than is often supposed4 ,berkeley1 as everyone knows1 denied the reality of matter1 and maintained that everything is mental4 ,in the former respect ,i agree with him1 though not for his reasons2 in the latter respect1 ,i think his argument unsound and his conclusion improbable1 though not certainly false4 ,however1 ,i will leave the development of my own views to a later chapter1 and confine myself to ,berkeley's argument4 ,berkeley contended that when1 for example1 you 8see a tree01 all that you really know to be happening is in you1 and is mental4 ,the colour that you see1 as ,locke had already argued1 does not belong to the physical world1 but is an effect upon you1 produced1 according to ,locke1 by a physical stimulus4 ,locke held that the purely spatial properties of perceived objects really belong to the objects1 whereas such things as colour1 softness1 sound1 etc41 are effects in us4 ,berkeley went further1 and argued that the spatial properties of perceived objects are no exception4 ,thus the object perceived is composed entirely of 8mental0 constituents1 and there is no reason to believe in the existence of anything not mental4 ,he did not wish to admit that a tree ceases to exist when we do not look at it1 so he maintained that it acquires permanence through being an idea in the mind of ,god4 ,it is still only an 8idea01 but not one whose existence depends upon the accidents of our perceptions4 ,the real objection to ,berkeley's view is rather physical than metaphysical4 ,light and sound take time to travel from their sources to the percipient1 and one must suppose that something is happening along the route by which they travel4 ,what is happening along the route is presumably not 8mental01 for1 as we have seen1 8mental0 events are those that have peculiar mnemic effects which are connected with living tissue4 ,therefore1 although ,berkeley is right in saying that the events we know immediately are mental1 it is highly probable that he is wrong as to the events which we infer in places where there are no living bodies4 ,in saying this1 however1 we are anticipating the results of a fuller discussion in a later chapter4 ,hume1 proceeding from a starting-point essentially similar to that of ,locke and ,berkeley1 arrived at conclusions so sceptical that all subsequent philosophers have shied away from them4 ,he denied the existence of the ,self1 questioned the validity of induction1 and doubted whether causal laws could be applied to anything except our own mental processes4 ,he is one of the very few philosophers not concerned to establish any positive conclusions4 ,to a great extent1 ,i think1 we must admit the validity of his reasons for refusing to feel the usual certainties4 ,as regards the ,self1 he was almost certainly right4 ,as we have already argued1 a person is not a single entity1 but a series of events linked together by peculiar causal laws4 ,as regards induction1 the question is very difficult1 and ,i shall devote a subsequent chapter to it4 ,as regards causal laws1 the question1 as we shall find later1 is the same as the question of induction4 ,on both points ,hume's doubts are not to be lightly dismissed4 ,the usual modern criticism of ,locke1 ,berkeley1 and ,hume is that they were unduly 8atomistic04 ,they thought of the mind as a collection of 8ideas01 each as hard and separate as a billiard-ball4 ,they had not the conception of continuous change or of integral processes2 their causal units were too small4 ,as we have already seen in connection with ,gestaltpsychologie and with sentences1 the causal unit is often a configuration which cannot be broken up without losing its distinctive causal properties4 ,in this sense1 it is true that the traditional ,british philosophy was too atomistic4 ,but in another sense ,i do not think it is true1 and ,i think much modern philosophy is confused on this point4 ,although a configuration may lose its causal properties when broken up into its elements1 it nevertheless does consist of these elements related in certain ways2 analysis into 8atoms0 is perfectly valid1 so long as it is not assumed that the causal efficacy of the whole is compounded out of the separate effects of the separate atoms4 ,it is because ,i hold this view that ,i call the philosophy which ,i advocate 8logical atomism04 ,and to this extent ,i regard ,locke1 ,berkeley1 and ,hume as in the right as against their modern critics4 ,but this also is a topic which will be resumed in a later chapter4 ,hume's criticism of the notion of cause was what led ,kant to his new departure4 ,kant's philosophy is difficult and obscure1 and philosophers still dispute as to what he meant4 ,those who disagree with him are held by his supporters to have misunderstood him2 ,i must therefore warn the reader that what follows is my view of what he meant1 and that there is no agreed view4 ,kant maintained that1 in virtue of our mental constitution1 we deal with the raw material of sense-impressions by means of certain 8categories0 and by arranging it in space and time4 ,both the categories and the space-time arrangement are supplied by us1 and do not belong to the world except as known by us4 ,but since our mental constitution is a constant datum1 all phenomena as known will be spatio-temporal and will conform to the categories4 ,among the latter 8cause0 is the most important4 ,thus although there may be no cause in the world as it is in itself 7a point on which ,kant was inconsistent in the interest of morals71 yet phenomena1 i4e4 things as they seem to us1 will always have other phenomena as their causes4 ,and although there is no time in the real world1 things as they appear to us will be some earlier and some later4 ,space1 again is supplied by us1 and therefore geometry can be known a priori1 without our having to study the outer world4 ,kant thought that ,euclidean geometry was quite certainly true1 although it could not be proved by logic alone1 since ,euclid's axioms could be denied without self-contradiction4 ,it was on this question of geometry that the weakness of ,kant's system first became obvious4 ,it was found that we have no grounds for regarding ,euclidean geometry as quite true4 ,since ,einstein1 we have positive grounds for regarding it as not quite true4 ,it appears that geometry is just as empirical as geography4 ,we depend upon observation if we want to know whether the sum of the angles of a triangle is two right angles just as much as if we want to know how much land there is in the western hemisphere4 ,with regard to the 8categories0 there are equally great difficulties4 ,let us take 8cause0 as our illustration4 ,we see lightning1 and then we hear thunder2 as phenomena1 our seeing and hearing are connected as cause and effect4 ,but we must not--if we are to take the subjectivity of 8cause0 seriously--suppose that our seeing or our hearing has an outside cause4 ,in that case1 we have no reason to suppose that there is anything outside ourselves4 ,nay1 more3 what really happens when we see is not1 according to ,kant1 what we perceive by introspection2 what really happens is something without a date1 without a position in space1 without causes and without effects4 ,thus we do not know ourselves any better than we know the outside world4 ,space and time and the categories interpose a mirage of illusion which cannot be penetrated at any point4 ,as an answer to ,hume's scepticism1 this seems a somewhat unsuccessful effort4 ,and ,kant himself1 later1 in the ,critique of ,practical ,reason1 demolished much of his own edifice1 because he thought that ethics at least must have validity in the 8real0 world4 ,this part of his philosophy1 however1 is usually ignored by his followers or apologetically minimised4 ,kant gave a new turn to an old philosophical controversy1 as to how far our knowledge is a priori and how far it is based on experience4 ,kant admitted that without experience we could know nothing1 and that what we know is only valid within the realm of experience4 ,but he held that the general framework of our knowledge is a priori in the sense that it is not proved by means of particular facts of experience1 but represents the conditions to which phenomena have to conform in order to be capable of being experienced4 ,before his day1 the tendency had been for continental philosophers to regard almost everything as a priori while ,british philosophers regarded almost everything as empirical4 ,but both sides thought that what is a priori can be proved by logic1 at least in theory1 whereas ,kant held that mathematics is a priori and yet 8synthetic01 i4e4 not capable of being proved by logic4 ,in this he was misled by geometry4 ,euclidean geometry1 considered as true1 is 8synthetic0 but not a priori2 considered merely as deducing consequences from premisses1 it is a priori but not 8synthetic04 ,the geometry of the actual world1 as required by engineers1 is empirical2 the geometry of pure mathematics1 which does not inquire into the truth of the axioms but merely shows their implications1 is an exercise in pure logic4 ,it should be said1 however1 that1 if the correct analysis of knowledge bears any resemblance at all to that which has been suggested in this book1 the whole controversy between empiricists and apriorists becomes more or less unreal4 ,all beliefs are caused by external stimuli2 when they are as particular as the stimuli they are of the sort which an empiricist might regard as proved by experience1 but when they are more general difficulties arise4 ,a foreigner arrives in ,america and sees the immigration officials1 who lead him to the generalisation that all ,americans are rude2 but a few minutes later the porter upsets this induction in the hope of a tip4 ,thus sometimes a given belief will be caused by one event and destroyed by another4 ,if all the events in a man's life1 so far as they affect the belief in question1 are such as to cause it1 he counts the belief true4 ,the more general a belief is1 the more events are relevant to it1 and therefore the more difficult it is for it to be such as a man will long consider true4 ,roughly speaking1 the beliefs which count as a priori will be those which well might have been upset by subsequent events1 but in fact were confirmed4 ,here as elsewhere we are driven to the view that theory of knowledge is not so fundamental as it has been considered since ,kant4 ,there is one more traditional controversy which ,i wish to consider1 namely1 that between monists and pluralists4 ,is the universe one1 or is it many8 ,if many1 how intimately are they interconnected8 ,the monistic view is very old3 it is already complete in ,parmenides 7fifth century ,b4,c474 ,it is fully developed in ,spinoza1 ,hegel1 and ,bradley4 ,the pluralistic view1 on the other hand1 is found in ,heraclitus1 the atomists1 ,leibniz1 and the ,british empiricists4 ,for the sake of definiteness1 let us take the monistic view as found in ,bradley1 who is in the main a follower of ,hegel4 ,he maintains that every judgment consists in assigning a predicate to ,reality as a whole3 the whole is the subject of every predicate4 ,suppose you start by saying 8,tommy has a cold in the head04 ,this may not seem to be a statement about the universe as a whole1 but according to ,bradley it is4 ,if ,i may be allowed to set forth his argument in popular language which his followers might resent1 ,i should put it something like this3 ,first of all1 who is ,tommy8 ,he is a person with a certain nature1 distinguished from other persons by that nature2 he may resemble others in many respects1 but not in all1 so that you cannot really explain who ,tommy is unless you set forth all his characteristics4 ,but when you try to do this1 you are taken beyond ,tommy3 he is characterised by relations to his environment4 ,he is affectionate or rebellious or thirsty1 noisy or quiet1 and so on2 all of these qualities involve his relations to others4 ,if you try to define ,tommy without mentioning anything outside him1 you will find this quite impossible2 therefore he is not a self-subsistent being1 but an unsubstantial fragment of the world4 ,the same thing applies even more obviously to his nose and his cold4 ,how do you know he has a cold8 ,because material substances of a certain kind pass from his nose to his handkerchief1 which would not be possible if he alone existed4 ,but now1 when you take in the environment with a view to defining ,tommy and his nose and his cold1 you find that you cannot define his immediate environment without taking account of its environment1 and so on1 until at last you have been forced to include the whole world4 ,therefore ,tommy's cold is in reality a property of the world1 since nothing short of the world is sufficiently substantial to have properties4 ,we may put the argument in a more abstract form4 ,everything which is part of the world is constituted1 in part1 by its relations to other things2 but relations cannot be real4 ,bradley's argument against relations is as follows4 ,first he argues that1 if there are relations1 there must be qualities between which they hold4 ,this part of the argument need not detain us4 ,he then proceeds3 8,but how the relation can stand to the qualities is1 on the other side1 unintelligible4 ,if it is nothing to the qualities1 then they are not related at all2 and1 if so1 as we saw1 they have ceased to be qualities1 and their relation is a nonentity4 ,but if it is to be something to them1 then clearly we shall require a new-connecting relation4 ,for the relation hardly can be the mere adjective of one or both of its terms2 or1 at least1 as such it seems indefensible4 ,and1 being something itself1 if it does not itself bear a relation to the terms1 in what intelligible way will it succeed in being anything to them8 ,but here again we are hurried off into the eddy of a hopeless process1 since we are forced to go on finding new relations without end4 ,the links are united by a link1 and this bond of union is a link which also has two ends2 and these require each a fresh link to connect them with the old4 ,the problem is to find how the relation can stand to its qualities1 and this problem is insoluble40 ,i cannot deal adequately with this argument without abstruse technicalities which would be out of place4 ,i will1 however1 point out what seems to me the essential error4 ,bradley conceives a relation as something just as substantial as its terms1 and not radically different in kind4 ,the analogy of the chain with links should make us suspicious1 since it clearly proves1 if it is valid1 that chains are impossible1 and yet1 as a fact1 they exist4 ,there is not a word in his argument which would not apply to physical chains4 ,the successive links are united not by another link1 but by a spatial relation4 ,i think ,bradley has been misled1 unconsciously1 by a circumstance to which ,i alluded in an earlier chapter1 namely1 the fact that the word for a relation is as substantial as the words for its terms4 ,suppose ,a and ,b are two events1 and ,a precedes ,b4 ,in the proposition 8,a precedes ,b01 the word 8precedes0 is just as substantial as the words 8,a0 and 8,b04 ,the relation of the two events ,a and ,b is represented1 in language1 by the time or space order of the three words 8,a01 8precedes01 and 8,b04 ,but this order is an actual relation1 not a word for relation4 ,the first step in ,bradley's regress does actually have to be taken in giving verbal expression to a relation1 and the word for a relation does have to be related to the words for its terms4 ,but this is a linguistic1 not a metaphysical1 fact1 and the regress does not have to go any further4 ,it should be added that1 as ,bradley himself recognises1 his difficulties break out afresh when he comes to consider the relation of subject and predicate when a character is assigned to ,reality1 and that he is therefore compelled to conclude that no truth is quite true4 ,a conclusion of this sort1 based upon an extremely abstract argument1 makes it natural to suspect that there is some error in the argument4 ,pluralism is the view of science and common sense1 and is therefore to be accepted if the arguments against it are not conclusive4 ,for my part1 ,i have no doubt whatever that it is the true view1 and that monism is derived from a faulty logic inspired by mysticism4 ,this logic dominates the philosophy of ,hegel and his followers2 it is also the essential basis of ,bergson's system1 although it is seldom mentioned in his writings4 ,when it is rejected1 ambitious metaphysical systems such as those of the past are seen to be impossible4 ,,chapter ,,xxiv ,,truth ,,and ,,falsehood ,the question of truth and falsehood has been wrapped in unnecessary mystery owing to a number of causes4 ,in the first place1 people wish to think that their beliefs are more apt to be true than false1 so that they seek a theory that will show that truth is normal and falsehood more or less accidental4 ,in the second place1 people are very vague as to what they mean by 8belief0 or 8judgment01 though persuaded that they know beliefs or judgments to be the objects to which the predicates 8true0 or 8false0 apply4 ,in the third place1 there is a tendency to use 8truth0 with a big ,t in the grand sense1 as something noble and splendid and worthy of adoration4 ,this gets people into a frame of mind in which they become unable to think4 ,but just as the grave-diggers in ,hamlet became familiar with skulls1 so logicians become familiar with truth4 8,the hand of little employment hath the daintier sense10 says ,hamlet4 ,therefore it is not from the logician that awe before truth is to be expected4 ,there are two questions in our present subject3 7#a7 ,what are the objects to which the predicates 8true0 and 8false0 apply8 7#b7 ,what is the difference between such as are true and such as are false8 ,we will begin with the first of these questions4 ,prima facie1 8true0 and 8false0 apply to statements1 whether in speech or in writing4 ,by extension1 they are supposed to apply to the beliefs expressed in those statements1 and also to hypotheses which are entertained without being believed or disbelieved4 ,but let us first consider the truth and falsehood of statements1 following our practice of going as far as we can with the behaviourists before falling back on introspection4 ,we considered the meaning of words earlier2 now we have to consider sentences4 ,of course a sentence may consist of a single word1 or of a wink2 but generally it consists of several words4 ,in that case1 it has a meaning which is a function of the meanings of the separate words and their order4 ,a sentence which has no meaning is not true or false2 thus it is only sentences as vehicles of a certain sort of meaning that have truth or falsehood4 ,we have therefore to examine the meaning of a sentence4 ,let us take some very humble example4 ,suppose you look in a time-table and find it there stated that a passenger train leaves ,king's ,cross for ,edinburgh at #aj ,a4,m4 ,what is the meaning of this assertion8 ,i shudder when ,i think of its complexity4 ,if ,i were to try to develop the theme adequately1 ,i should be occupied with nothing else till the end of the present volume1 and then ,i should have only touched the fringe of the subject4 ,take first the social aspect3 it is not essential that anybody but the engineer and fireman should travel by the train1 though it is essential that others should be able to travel by it if they fulfil certain conditions4 ,it is not essential that the train should reach ,edinburgh3 the statement remains true if there is an accident or breakdown on the way4 ,but it is essential that the management of the railway should intend it to reach ,edinburgh4 ,take next the physical aspect3 it is not essential1 or even possible1 that the train should start exactly at ten2 one might perhaps say that it must not start more than ten seconds before its time or more than fifty seconds after1 but these limits cannot be laid down rigidly4 ,in countries where unpunctuality is common they would be much wider4 ,then we must consider what we mean by 8starting01 which no one can define unless he has learnt the infinitesimal calculus4 ,then we consider the definitions of ,king's ,cross and ,edinburgh1 both of which are more or less vague terms4 ,then we must consider what is meant by a 8train04 ,here there will be first of all complicated legal questions2 what constitutes fulfilment of a railway company's obligations in the way of running 8trains08 ,then there are questions as to the constitution of matter1 since evidently a train is a piece of matter2 also of course there are questions as to methods of estimating ,greenwich time at ,king's ,cross4 ,most of the above points have to do with the meaning of single words1 not with the meaning of the whole sentence4 ,it is obvious that the ordinary mortal does not trouble about such complications when he uses the words3 to him a word has a meaning very far from precise1 and he does not try to exclude marginal cases4 ,it is the search for precision that introduces complications4 ,we think we attach a meaning to the word 8man01 but we don't know whether to include ,pithecanthropus ,erectus4 ,to this extent1 the meaning of the word is vague4 ,as knowledge increases1 words acquire meanings which are more precise and more complex2 new words have to be introduced to express the less complex constituents which have been discovered4 ,a word is intended to describe something in the world2 at first it does so very badly1 but afterwards it gradually improves4 ,thus single words embody knowledge1 although they do not make assertions4 ,in an ideal logical language1 there will be words of different kinds4 ,first1 proper names4 ,of these1 however1 there are no examples in actual language4 ,the words which are called proper names describe collections1 which are always defined by some characteristic2 thus assertions about 8,peter0 are really about everything that is 8,peterish04 ,to get a true proper name1 we should have to get to a single particular or a set of particulars defined by enumeration1 not by a common quality4 ,since we cannot acquire knowledge of actual particulars1 the words we use denote1 in the best language we can make1 either adjectives or relations between two or more terms4 ,in addition to these1 there are words indicative of structure3 e4g4 in 8,a is greater than ,b01 the words 8is0 and 8than0 have no separate meaning1 but merely serve to show the 8sense0 of the relation 8greater01 i4e4 that it goes from ,a to ,b1 not from ,b to ,a4 ,strictly speaking1 we are still simplifying4 ,true adjectives and relations will require particulars for their terms2 the sort of adjectives we can know1 such as 8blue0 and 8round01 will not be applicable to particulars4 ,they are therefore analogous to the adjective 8populous0 applied to a town4 ,to say 8this town is populous0 means 8many people live in this town04 ,a similar transformation would be demanded by logic in all the adjectives and relations we can know empirically4 ,that is to say1 no word that we can understand would occur in a grammatically correct account of the universe4 ,leaving on one side the vagueness and inaccuracy of words1 let us ask ourselves2 in what circumstances do we feel convinced that we know a statement to be true or false as the case may be8 ,a present statement will be regarded as true if1 e4g4 it agrees with recollection or perception2 a past statement1 if it raised expectations now confirmed4 ,i do not mean to say that these are the only grounds upon which we regard statements as true2 ,i mean that they are simple and typical1 and worth examining4 ,if you say 8it was raining this morning01 ,i may recollect that it was or that it wasn't4 ,one may perhaps say that the words 8this morning0 are associated for me with the word 8raining0 or with the words 8not raining04 ,according to which occurs1 ,i judge your statement true or false4 ,if ,i have neither association1 ,i do not judge your statement either true or false unless ,i have material for an inference2 and ,i do not wish to consider inference yet4 ,if you say 8the lights have gone out01 when ,i can see the lights shining1 ,i judge that you speak falsely1 because my perception is associated with the words 8lights shining04 ,if you say 8the lights will go out in a minute01 you produce a certain familiar kind of tension called 8expectation01 and after a time you produce a judgment that you spoke falsely 7if the lights do not go out74 ,these are the ordinary direct ways of deciding on the truth or falsehood of statements about past1 present1 or future4 ,it is necessary to distinguish between direct and indirect grounds for accepting or rejecting statements4 ,pragmatism considers only indirect grounds4 ,broadly speaking1 it considers a statement false when the consequences of accepting it are unfortunate4 ,but this belongs to the region of inference4 ,i ask you the way to the station1 you tell me wrong1 and ,i miss my train2 ,i then infer that you told me wrong4 ,but if you say 8the lights are out0 when ,i see them shining1 ,i reject your statement without inference4 ,in this case1 something in my present circumstances is associated with words different from yours1 and different in ways which ,i have learnt to regard as involving incompatibility4 ,the ultimate test of falsehood is never1 so ,i think1 the nature of the consequences of a belief1 but the association between words and sensible or remembered facts4 ,a belief is 8verified0 when a situation arises which gives a feeling of expectedness in connection with it2 it is falsified when the feeling is one of surprise4 ,but this only applies to beliefs which await some future contingency for verification or refutation4 ,a belief which is an immediate reaction to a situation--e4g4 when you are waiting for a race to begin and presently you say 8they're off0--has no need of verification1 but verifies other beliefs4 ,and even where the confirmation of a belief is in the future1 it is the expectedness1 not the pleasantness1 of the consequences that confirms the truth of the belief4 ,i think it is a mistake to treat 8belief0 as one kind of occurrence1 as is done in traditional psychology4 ,the sort of belief which is based upon memory or perception alone differs from the sort which involves expectation4 ,when you find in the time-table that a train leaves ,king's ,cross at ten1 your belief that this statement occurs in the time-table does not await future confirmation1 but your belief about the train does3 you may go to ,king's ,cross and see the train start4 ,a belief which concerns an event may be a recollection1 a perception1 or an expectation4 ,it may be none of these1 in the case of an event which you have not seen and do not expect to see--e4g4 ,csar crossing the ,rubicon1 or the abolition of the ,house of ,lords4 ,but such beliefs always involve inference4 ,i do not at this stage consider logical and mathematical beliefs1 some of which must be1 in a sense1 non-inferential4 ,but ,i think we shall find that this sense is different from that in which memories and perceptions are non-inferential4 ,a belief1 ,i should say1 interpreted narrowly1 is a form of words related to an emotion of one of several kinds4 7,i shall give a broader meaning later47 ,the emotion is different according as the belief embodies a reminiscence1 a perception1 an expectation1 or something outside the experience of the believer4 ,moreover1 a form of words is not essential4 ,where the emotion is present1 and leads to action relevant to some feature of the environment1 there may be said to be a belief4 ,the fundamental test of a belief1 of no matter what sort1 is that it causes some event which actually takes place to arouse the emotion of expectedness or its opposite4 ,i do not now attempt to decide what an emotion is4 ,dr4 ,watson gives a behaviouristic account of emotions1 which would1 if adopted1 make my definition of 8belief0 purely behaviouristic4 ,i have framed the definition so as not to involve a decision on the question of introspection4 ,the subject of truth and falsehood may be subdivided as follows3 ,a4 ,formal ,theory4--,given the meanings of the component words1 what decides whether a sentence is true or false8 ,b4 ,causal ,theory4--,can we distinguish between truth and falsehood by 7a7 their causes1 7b7 their effects8 ,c4 ,individual and ,social ,elements4--,a statement is a social occurrence1 a belief is something individual4 ,how can we define a belief1 and what is it when not composed of words8 ,d4 ,consistency and ,truth4--,can we get outside the circle of beliefs or statements to something else which shows them true1 not merely consistent8 ,in other words1 what possible relation is there between propositions and facts8 ,it is very hard to disentangle these questions4 ,the first question1 as to formal theories1 leads to the fourth1 as to the relations of propositions to facts4 ,e4g4 8,brutus killed ,csar0 is true because of a certain fact2 what fact8 ,the fact that ,brutus killed ,csar4 ,this keeps us in the verbal realm1 and does not get us outside it to some realm of non-verbal fact by which verbal statements can be verified4 ,hence our fourth problem arises4 ,but this leads us to our second problem1 as to causes and effects of what is true or false1 for it is here that we shall naturally look for the vital relation between propositions and facts4 ,and here again we must distinguish between thinking truly and speaking truly4 ,the former is an individual affair1 the latter a social affair4 ,thus all our problems hang together4 ,i will begin with ,c1 the difference between a belief and a statement4 ,by a 8statement0 ,i mean a form of words1 uttered or written1 with a view to being heard or read by some other person or persons1 and not a question1 interjection1 or command1 but such as we should call an assertion4 ,as to the question what forms of words are assertions1 that is one for the grammarian and differs from language to language4 ,but perhaps we can say rather more than that4 ,the distinction1 however1 between an assertion and an imperative is not sharp4 ,in ,england1 notices say 8,visitors are requested not to walk on the grass04 ,in ,america1 they say 8,keep off6 ,this means you40 ,effectively1 the two have the same meaning3 yet the ,english notice consists only of a statement1 while the ,american notice consists of an imperative followed by a statement which must be false if read by more than one person4 ,in so far as statements are intended to influence the conduct of others1 they partake of the nature of imperatives or requests4 ,their characteristic1 however1 is that they endeavour to effect their aim by producing a belief which may or may not exist in the mind of the speaker4 ,often1 however1 they express a belief1 without stopping to consider the effect upon others4 ,thus a statement may be defined as a form of words which either expresses a belief or is intended to create one4 ,our next step1 therefore1 must be the definition of 8belief04 8,belief0 is a word which will be quite differently defined if we take an analytic point of view from the way in which we shall define it if we regard the matter causally4 ,from the point of view of science1 the causal point of view is the more important4 ,beliefs influence action in certain ways2 what influences action in these ways may be called a belief1 even if1 analytically1 it does not much resemble what would ordinarily be so called4 ,we may therefore widen our previous definition of belief4 ,consider a man who goes to the house where his friend used to live1 and1 finding he has moved1 says1 8,i thought he still lived here01 whereas he acted merely from habit without thought4 ,if we are going to use words causally1 we ought to say that this man had a 8belief0 and therefore a 8belief0 will be merely a characteristic of a string of actions4 ,we shall have to say3 ,a man 8believes0 a certain proposition p if1 whenever he is aiming at any result to which p is relevant1 he acts in a manner calculated to achieve the result if p is true1 but not otherwise4 ,sometimes this gives definite results1 sometimes not4 ,when you call a telephone number1 it is clear that you believe that to be the number of the subscriber you want4 ,but whether you believe in the conservation of energy or a future life may be harder to decide4 ,you may hold a belief in some contexts and not in others2 for we do not think in accordance with the so-called 8,laws of ,thought04 8,belief0 like all the other categories of traditional psychology1 is a notion incapable of precision4 ,this brings me to the question whether the truth or falsehood of a belief can be determined either by its causes or by its effects4 ,there is1 however1 a preliminary difficulty4 ,i said just now that ,a believes p if he acts in a way which will achieve his ends if p is true4 ,i therefore assumed that we know what is meant by 8truth04 ,i assumed1 to be definite1 that we know what is meant by 8truth0 as applied to a form of words4 ,the argument was as follows3 ,from observation of a person's acts1 you infer his beliefs1 by a process which may be elaborate as the discovery of ,kepler's ,laws from the observed motions of the planets4 ,his 8beliefs0 are not assumed to be 8states of mind01 but merely characteristics of series of actions4 ,these beliefs1 when ascertained by observation1 can be expressed in words2 you can say1 e4g4 8,this person believes that there is a train from ,king's ,cross at #aj ,a4,m40 ,having once expressed the belief in words of which the meaning is known1 you have arrived at the stage where formal theories are applicable4 ,words of known meaning1 put together according to a known syntax1 are true or false in virtue of some fact1 and their relation to this fact results logically from the meanings of the separate words and the laws of syntax4 ,this is where logic is strong4 ,it will be seen that1 according to what we have said1 truth is applicable primarily to a form of words1 and only derivatively to a belief4 ,a form of words is a social phenomenon1 therefore the fundamental form of truth must be social4 ,a form of words is true when it has a certain relation to a certain fact4 ,what relation to what fact8 ,i think the fundamental relation is this3 a form of words is true if a person who knows the language is led to that form of words when he finds himself in an environment which contains features that are the meanings of those words1 and these features produce reactions in him sufficiently strong for him to use words which mean them4 ,thus 8a train leaves ,king's ,cross at #aj ,a4,m40 is true if a person can be led to say1 8,it is now #aj ,a4,m41 this is ,king's ,cross1 and ,i see a train starting04 ,the environment causes words1 and words directly caused by the environment 7if they are statements7 are 8true04 ,what is called 8verification0 in science consists in putting oneself in a situation where words previously used for other reasons result directly from the environment4 ,of course1 given this basis1 there are innumerable indirect ways of verifying statements1 but all1 ,i think1 depend upon this direct way4 ,the above theory may be thought very odd1 but it is partly designed to meet the fourth of our previous questions1 namely1 8,how can we get outside words to the facts which make them true or false80 ,obviously we cannot do this within logic1 which is imprisoned in the realm of words2 we can only do it by considering the relations of words to our other experiences1 and these relations1 in so far as they are relevant1 can hardly be other than causal4 ,i think the above theory1 as it stands1 is too crude to be quite true4 ,we must also bring in such things as expectedness1 which we discussed earlier4 ,but ,i believe that the definition of truth or falsehood will have to be sought along some such lines as ,i have indicated4 ,i want in conclusion to indulge in two speculations4 ,the first concerns a possible reconciliation of behaviourism and logic4 ,it is clear that1 when we have a problem to solve1 we do not always solve it as the rat does1 by means of random movements2 we often solve it by 8thinking01 i4e4 by a process in which we are not making any overt movements4 ,the same thing was sometimes true of ,khler's chimpanzees4 ,now what is involved in the possibility of solving a problem by verbal thinking8 ,we put words together in various ways which are not wholly random1 but limited by previous knowledge of the sort of phrase that is likely to contain a solution of our problem4 ,at last we hit upon a phrase which seems to give what we want4 ,we then proceed to an overt action of the kind indicated by the phrase2 if it succeeds1 our problem is solved4 ,now this process is only intelligible if there is some connection between the laws of syntax and the laws of physics--using 8syntax0 in a psychological rather than a grammatical sense4 ,i think this connection is assumed in logic and ordinary philosophy1 but it ought to be treated as a problem requiring investigation by behaviourist methods4 ,i lay no stress on this suggestion1 except as giving a hint for future investigations4 ,but ,i cannot think that the behaviourist has gone far towards the solution of his problem until he has succeeded in establishing a connection between syntax and physics4 ,without this1 the efficacy of 8thought0 cannot be explained on his principles4 ,my second speculation is as to the limitations which the structure of language imposes upon the extent of our possible knowledge of the world4 ,i am inclined to think that quite important metaphysical conclusions1 of a more or less sceptical kind1 can be drawn from simple considerations as to the relation between language and things4 ,a spoken sentence consists of a temporal series of events2 a written sentence is a spatial series of bits of matter4 ,thus it is not surprising that language can represent the course of events in the physical world2 it can1 in fact1 make a map of the physical world1 preserving its structure in a more manageable form1 and it can do this because it consists of physical events4 ,but if there were such a world as the mystic postulates1 it would have a structure different from that of language1 and would therefore be incapable of being verbally described4 ,it is fairly clear that nothing verbal can conform or confute this hypothesis4 ,a great deal of the confusion about relations which has prevailed in practically all philosophies comes from the fact that relations are indicated1 not by relations1 but by words which are as substantial as other words4 ,consequently1 in thinking about relations1 we constantly hover between the unsubstantiality of the relation itself and the substantiality of the word4 ,take1 say1 the fact that lightning precedes thunder4 ,we saw earlier that to express this by a language closely reproducing the structure of the fact1 we should have to say simply3 8lightning1 thunder01 where the fact that the first word precedes the second means that what the first word means precedes what the second word means4 ,but even if we adopted this method for temporal order1 we should still need words for all other relations1 because we could not without intolerable ambiguity symbolise them also by the order of our words4 ,when we say 8lightning precedes thunder01 the word 8precedes0 has a quite different relation to what it means from that which the words 8lightning0 and 8thunder0 have to what they respectively mean4 ,wittgenstein#ab says that what really happens is that we establish a relation between the word 8lightning0 and the word 8thunder01 namely the relation of having the word 8precedes0 between them4 ,in this way he causes relations to be symbolised by relations4 ,but although this may be quite correct1 it is sufficiently odd to make it not surprising that people have thought the word 8precedes0 means a relation in the same sense in which 8lightning0 means a kind of event4 ,this view1 however1 must be incorrect4 ,i think it has usually been held unconsciously1 and has produced many confusions about relations which cease when it is exposed to the light of day--for example1 those which lead ,bradley to condemn relations4 #ab ,tractatus ,logico-,philosophicus 7,kegan ,paul74 ,in all this ,i have been considering the question of the relation between the structure of language and the structure of the world4 ,it is clear that anything that can be said in an inflected language can be said in an uninflected language2 therefore1 everything that can be said in language can be said by means of a temporal series of uninflected words4 ,this places a limitation upon what can be expressed in words4 ,it may well be that there are facts which do not lend themselves to this very simple schema2 if so1 they cannot be expressed in language4 ,our confidence in language is due to the fact that it consists of events in the physical world1 and1 therefore1 shares the structure of the physical world1 and therefore can express that structure4 ,but if there be a world which is not physical1 or not in space-time1 it may have a structure which we can never hope to express or to know4 ,these considerations might lead us to something like the ,kantian a priori1 not as derived from the structure of the mind1 but as derived from the structure of language1 which is the structure of the physical world4 ,perhaps that is why we know so much physics and so little of anything else4 ,however1 ,i have lapsed into mystical speculation1 and will leave these possibilities1 since1 by the nature of the case1 ,i cannot say anything true about them4 ,,chapter ,,xxv ,,the ,,validity ,,of ,,inference ,it is customary in science to regard certain facts as 8data01 from which laws and also other facts are 8inferred04 ,we saw in ,chapter ,,vii that the practice of inference is much wider than the theories of any logician would justify1 and that it is nothing other than the law of association or of 8learned reactions04 ,in the present chapter1 ,i wish to consider what the logicians have evolved from this primitive form of inference1 and what grounds we have1 as rational beings1 for continuing to infer4 ,but let us first get as clear a notion as we can of what should be meant by a 8datum04 ,the conception of a 8datum0 cannot be made absolute4 ,theoretically1 it should mean something that we know without inference4 ,but before this has any definite meaning1 we must define both 8knowledge0 and 8inference04 ,both these terms have been considered in earlier chapters4 ,for our present purpose it will simplify matters to take account only of such knowledge as is expressed in words4 ,we considered in ,chapter ,,xxiv the conditions required in order that a form of words may be 8true02 for present purposes1 therefore1 we may say that 8knowledge0 means 8the assertion of a true form of words04 ,this definition is not quite adequate1 since a man may be right by chance2 but we may ignore this complication4 ,we may then define a 8datum0 as follows3 ,a 8datum0 is a form of words which a man utters as the result of a stimulus1 with no intermediary of any learned reaction beyond what is involved in knowing how to speak4 ,we must1 however1 permit such learned reactions as consist in adjustments of the sense-organs or in mere increase of sensitivity4 ,these merely improve the receptivity to data1 and do not involve anything that can be called inference4 ,if the above definition is accepted1 all our data for knowledge of the external world must be of the nature of percepts4 ,the belief in external objects is a learned reaction acquired in the first months of life1 and it is the duty of the philosopher to treat it as an inference whose validity must be tested4 ,a very little consideration shows that1 logically1 the inference cannot be demonstrative1 but must be at best probable4 ,it is not logically impossible that my life may be one long dream1 in which ,i merely imagine all the objects that ,i believe to be external to me4 ,if we are to reject this view1 we must do so on the basis of an inductive or analogical argument1 which cannot give complete certainty4 ,we perceive other people behaving in a manner analogous to that in which we behave1 and we assume that they have had similar stimuli4 ,we may hear a whole crowd say 8oh0 at the moment when we see a rocket burst1 and it is natural to suppose that the crowd saw it too4 ,nor are such arguments confined to living organisms4 ,we can talk to a dictaphone and have it afterwards repeat what we said2 this is most easily explained by the hypothesis that at the surface of the dictaphone events happened1 while ,i was speaking1 which were closely analogous to those that were happening just outside my ears4 ,it remains possible that there is no dictaphone and ,i have no ears and there is no crowd watching the rocket2 my percepts may be all that is happening in such cases4 ,but1 if so1 it is difficult to arrive at any causal laws1 and arguments from analogy are more misleading than we are inclined to think them4 ,as a matter of fact1 the whole structure of science1 as well as the world of common sense1 demands the use of induction and analogy if it is to be believed4 ,these forms of inference1 therefore1 rather than deduction1 are those that must be examined if we are to accept the world of science or any world outside of our own dreams4 ,let us take a simple example of an induction which we have all performed in practice4 ,if we are hungry1 we eat certain things we see and not others--it may be said that we infer edibility inductively from a certain visual and olfactory appearance4 ,the history of this process is that children a few months old put everything into their mouths unless they are stopped2 sometimes the result is pleasant1 sometimes unpleasant2 they repeat the former rather than the latter4 ,that is to say3 given that an object having a certain visual and olfactory appearance has been found pleasant to eat1 an object having a very similar appearance will be eaten2 but when a certain appearance has been found connected with unpleasant consequences when eaten1 a similar appearance does not lead to eating next time4 ,the question is3 what logical justification is there for our behaviour8 ,given all our past experience1 are we more likely to be nourished by bread than by a stone8 ,it is easy to see why we think so1 but can we1 as philosophers justify this way of thinking8 ,it is1 of course1 obvious that unless one thing can be a sign of another both science and daily life would be impossible4 ,more particularly1 reading involves this principle4 ,one accepts printed words as signs1 but this is only justifiable by means of induction4 ,i do not mean that induction is necessary to establish the existence of other people1 though that also1 as we have seen1 is true4 ,i mean something simpler4 ,suppose you want your hair cut1 and as you walk along the street you see a notice 8hair-cutting1 first floor04 ,it is only by means of induction that you can establish that this notice makes it in some degree probable that there is a hair-cutter's establishment on the first floor4 ,i do not mean that you employ the principle of induction2 ,i mean that you act in accordance with it1 and that you would have to appeal to it if you were accompanied by a long-haired sceptical philosopher who refused to go upstairs till he was persuaded there was some point in doing so4 ,the principle of induction1 prima facie1 is as follows3 ,let there be two kinds of events1 ,a and ,b 7e4g4 lightning and thunder71 and let many instances be known in which an event of the kind ,a has been quickly followed by one of the kind ,b1 and no instances of the contrary4 ,then either a sufficient number of instances of this sequence1 or instances of suitable kinds will make it increasingly probable that ,a is always followed by ,b1 and in time the probability can be made to approach certainty without limit provided the right kind and number of instances can be found4 ,this is the principle we have to examine4 ,scientific theories of induction generally try to substitute well-chosen instances for numerous instances1 and represent number of instances as belonging to crude popular induction4 ,but in fact popular induction depends upon the emotional interest of the instances1 not upon their number4 ,a child who has burnt its hand once in a candle-flame establishes an induction1 but words take longer1 because at first they are not emotionally interesting4 ,the principle used in primitive practice is3 ,whatever1 on a given occasion1 immediately precedes something very painful or pleasant1 is a sign of that interesting event4 ,number plays a secondary part as compared with emotional interest4 ,that is one reason why rational thought is so difficult4 ,the logical problem of induction is to show that the proposition 8,a is always accompanied 7or followed7 by ,b0 can be rendered probable by knowledge of instances in which this happens1 provided the instances are suitably chosen or very numerous4 ,far the best examination of induction is contained in ,mr4 ,j4 ,m4 ,keynes's ,treatise on ,probability4 ,there is a valuable doctor's thesis by the late ,jean ,nicod1 ,le ,problme logique de l'induction1 which is very ably reviewed by ,r4 ,b4 ,braithwaite in ,mind1 ,october #aibe4 ,a man who reads these three will know most of what is known about induction4 ,the subject is technical and difficult1 involving a good deal of mathematics1 but ,i will attempt to give the gist of the results4 ,we will begin with the condition in which the problem had been left by ,j4 ,s4 ,mill4 ,he had four canons of induction1 by means of which1 given suitable examples1 it could be demonstrated that ,a and ,b were causally connected1 if the law of causation could be assumed4 ,that is to say1 given the law of causation1 the scientific use of induction could be reduced to deduction4 ,roughly the method is this3 ,we know that ,b must have a cause2 the cause cannot be ,c or ,d or ,e1 etc41 because we find by experiment or observation that these may be present without producing ,b4 ,on the other hand1 we never succeed in finding ,a without its being accompanied 7or followed7 by ,b4 ,if ,a and ,b are both capable of quantity1 we may find further that the more there is of ,a the more there is of ,b4 ,by such methods we eliminate all possible causes except ,a2 therefore1 since ,b must have a cause1 that cause must be ,a4 ,all this is not really induction at all2 true induction only comes in in proving the law of causation4 ,this law ,mill regards as proved by mere enumeration of instances3 we know vast numbers of events which have causes1 and no events which can be shown to be uncaused2 therefore1 it is highly probable that all events have causes4 ,leaving out of account the fact that the law of causality cannot have quite the form that ,mill supposed1 we are left with the problem3 ,does mere number of instances afford a basis for induction8 ,if not1 is there any other basis8 ,this is the problem to which ,mr4 ,keynes addresses himself4 ,mr4 ,keynes holds that an induction may be rendered more probable by number of instances1 not because of their mere number1 but because of the probability1 if the instances are very numerous1 that they will have nothing in common except the characteristics in question4 ,we want1 let us suppose1 to find out whether some quality ,a is always associated with some quality ,b4 ,we find instances in which this is the case2 but it may happen that in all our instances some quality ,c is also present1 and that it is ,c that is associated with ,b4 ,if we can so choose our instances that they have nothing in common except the qualities ,a and ,b1 then we have better grounds for holding that ,a is always associated with ,b4 ,if our instances are very numerous1 then1 even if we do not know that they have no other common quality1 it may become quite likely that this is the case4 ,this1 according to ,mr4 ,keynes1 is the sole value of many instances4 ,a few technical terms are useful4 ,suppose we want to establish inductively that there is some probability in favour of the generalisation3 8,everything that has the property ,f also has the property f04 ,we will call this generalisation g4 ,suppose we have observed a number of instances in which ,f and f go together1 and no instances to the contrary4 ,these instances may have other common properties as well2 the sum-total of their common properties is called the total positive analogy1 and the sum-total of their known common qualities is called the known positive analogy4 ,the properties belonging to some but not to all of the instances in question are called the negative analogy3 all of them constitute the total negative analogy1 all those that are known constitute the known negative analogy4 ,to strengthen an induction1 we want to diminish the positive analogy to the utmost possible extent2 this1 according to ,mr4 ,keynes1 is why numerous instances are useful4 ,on 8pure0 induction1 where we rely solely upon number of instances1 without knowing how they affect the analogy1 ,mr4 ,keynes concludes 7,treatise in ,probability1 p4 #bcf73 8,we have shown that if each of the instances necessarily follows from the generalisation1 then each additional instance increases the probability of the generalisation1 so long as the new instance could not have been predicted with certainty from a knowledge of the former instances4444 ,the common notion1 that each successive verification of a doubtful principle strengthens it1 is formally proved1 therefore without any appeal to conceptions of law or of causality4 ,but we have not proved that this probability approaches certainty as a limit1 or even that our conclusion becomes more likely than not1 as the number of verifications or instances is indefinitely increased40 ,it is obvious that induction is not much use unless1 with suitable care1 its conclusions can be rendered more likely to be true than false4 ,this problem therefore necessarily occupies ,mr4 ,keynes4 ,it is found that an induction will approach certainty as a limit if two conditions are fulfilled3 7#a7 ,if the generalisation is false1 the probability of its being true in a new instance when it has been found to be true in a certain number of instances1 however great that number may be1 falls short of certainty by a finite amount4 7#b7 ,there is a finite a priori probability in favour of our generalisation4 ,mr4 ,keynes uses 8finite0 here in a special sense4 ,he holds that not all probabilities are numerically measurable2 a 8finite0 probability is one which exceeds some numerically measurable probability however small4 ,e4g4 our generalisation has a finite a priori probability if it is less unlikely than throwing heads a billion times running4 ,the difficulty is1 however1 that there is no easily discoverable way of estimating the a priori probability of a generalisation4 ,in examining this question1 ,mr4 ,keynes is led to a very interesting postulate which1 if true1 will1 he thinks1 give the required finite a priori probability4 ,his postulate as he gives it is not quite correct1 but ,i shall give his form first1 and then the necessary modification4 ,mr4 ,keynes supposes that the qualities of objects cohere in groups1 so that the number of independent qualities is much less than the total number of qualities4 ,we may conceive this after the analogy of biological species3 a cat has a number of distinctive qualities which are found in all cats1 a dog has a number of other distinctive qualities which are found in all dogs4 ,the method of induction can1 he says1 be justified if we assume 8that the objects in the field1 over which our generalisations extend1 do not have an infinite number of independent qualities2 that1 in other words1 their characteristics1 however numerous1 cohere together in groups of invariable connection1 which are finite in number0 7p4 #bef74 ,again 7p4 #beh73 8,as a biological foundation for ,analogy1 therefore1 we seem to need some such assumption as that the amount of variety in the universe is limited in such a way that there is no one object so complex that its qualities fall into an infinite number of independent groups 444 or rather that none of the objects about which we generalise are as complex as this2 or at least that1 though some objects may be infinitely complex1 we sometimes have a finite probability that an object about which we seek to generalise is not infinitely complex40 ,this postulate is called the 8principle of limitation of variety04 ,mr4 ,keynes again finds that it is needed in attempts to establish laws by statistics2 if he is right1 it is needed for all our scientific knowledge outside pure mathematics4 ,jean ,nicod pointed out that it is not quite sufficiently stringent4 ,we need1 according to ,mr4 ,keynes1 a finite probability that the object in question has only a finite number of independent qualities2 but what we really need is a finite probability that the number of its independent qualities is less than some assigned finite number4 ,this is a very different thing1 as may be seen by the following illustration4 ,suppose there is some number of which we know only that it is finite2 it is infinitely improbable that it will be less than a million1 or a billion1 or any other assigned finite number1 because1 whatever such number we take1 the number of smaller numbers is finite and the number of greater numbers is infinite4 ,nicod requires us to assume that there is a finite number n such that there is a finite probability that the number of independent qualities of our object is less than n4 ,this is a much stronger assumption than ,mr4 ,keynes's1 which is merely that the number of independent qualities is finite4 ,it is the stronger assumption which is needed to justify induction4 ,this result is very interesting and very important4 ,it is remarkable that it is in line with the trend of modern science4 ,eddington has pointed out that there is a certain finite number which is fundamental in the universe1 namely the number of electrons4 ,according to the quantum theory1 it would seem that the number of possible arrangements of electrons may well also be finite1 since they cannot move in all possible orbits1 but only in such as make the action in one complete revolution conform to the quantum principle4 ,if all this is true1 the principle of limitation of variety may well also be true4 ,we cannot1 however1 arrive at a proof of our principle in this way1 because physics uses induction1 and is therefore presumably invalid unless the principle is true4 ,what we can say1 in a general way1 is that the principle does not refute itself1 but1 on the contrary1 leads to results which confirm it4 ,to this extent1 the trend of modern science may be regarded as increasing the plausibility of the principle4 ,it is important to realise the fundamental position of probability in science4 ,at the very best1 induction and analogy only give probability4 ,every inference worthy of the name is inductive1 therefore all inferred knowledge is at best probable4 ,as to what is meant by probability1 opinions differ4 ,mr4 ,keynes takes it as a fundamental logical category3 certain premisses may make a conclusion more or less probable1 without making it certain4 ,for him1 probability is a relation between a premiss and a conclusion4 ,a proposition does not have a definite probability on its own account2 in itself1 it is merely true or false4 ,but it has probabilities of different amounts in regard to different premisses4 ,when we speak1 elliptically1 of the probability of a proposition1 we mean its probability in relation to all our relevant knowledge4 ,a proposition in probability cannot be refuted by mere observation3 improbable things may happen and probable things may fail to happen4 ,nor is an estimate of probability relevant to given evidence proved wrong when further evidence alters the probability4 ,for this reason the inductive principle cannot be proved or disproved by experience4 ,we might prove validly that such and such a conclusion was enormously probable1 and yet it might not happen4 ,we might prove invalidly that it was probable1 and yet it might happen4 ,what happens affects the probability of a proposition1 since it is relevant evidence2 but it never alters the probability relative to the previously available evidence4 ,the whole subject of probability1 therefore1 on ,mr4 ,keynes's theory1 is strictly a priori and independent of experience4 ,there is however another theory1 called the 8frequency theory01 which would make probability not indefinable1 and would allow empirical evidence to affect our estimates of probability relative to given premisses4 ,according to this theory in its crude form1 the probability that an object having the property ,f will have the property f is simply the proportion of the objects having both properties to all those having the property ,f4 ,for example1 in a monogamous country the probability of a married person being male is exactly a half4 ,mr4 ,keynes advances strong arguments against all forms of this theory that existed when his book was written4 ,there is however an article by ,r4 ,h4 ,nisbet on 8,the ,foundations of ,probability0 in ,mind for ,january #aibf1 which undertakes to rehabilitate the frequency theory4 ,his arguments are interesting1 and suffice to show that the controversy is still an open one1 but they do not1 in my opinion1 amount to decisive proof4 ,it is to be observed1 however1 that the frequency theory1 if it could be maintained1 would be preferable to ,mr4 ,keynes's1 because it would get rid of the necessity for treating probability as indefinable1 and would bring probability into much closer touch with what actually occurs4 ,mr4 ,keynes leaves an uncomfortable gap between probability and fact1 so that it is far from clear why a rational man will act upon a probability4 ,nevertheless1 the difficulties of the frequency theory are so considerable that ,i cannot venture to advocate it definitely4 ,meanwhile1 the details of the discussion are unaffected by the view we may take on this fundamental philosophical question4 ,and on either view the principle of limitation of variety will be equally necessary to give validity to the inferences by induction and analogy upon which science and daily life depend4 ,,chapter ,,xxvi ,,events1 ,,matter1 ,,and ,,mind ,everything in the world is composed of 8events02 that1 at least1 is the thesis ,i wish to maintain4 ,an 8event01 as ,i understand it1 is something having a small finite duration and a small finite extension in space2 or rather1 in view of the theory of relativity1 it is something occupying a small finite amount of space-time4 ,if it has parts1 these parts1 ,i say1 are again events1 never something occupying a mere point of instant1 whether in space1 in time1 or in space-time4 ,the fact that an event occupies a finite amount of space-time does not prove that it has parts4 ,events are not impenetrable1 as matter is supposed to be2 on the contrary1 every event in space-time is overlapped by other events4 ,there is no reason to suppose that any of the events with which we are familiar are infinitely complex2 on the contrary1 everything known about the world is compatible with the view that every complex event has a finite number of parts4 ,we do not know that this is the case1 but it is an hypothesis which cannot be refuted and is simpler than any other possible hypothesis4 ,i shall therefore adopt it as a working hypothesis in what follows4 ,when ,i speak of an 8event0 ,i do not mean anything out of the way4 ,seeing a flash of lightning is an event2 so is hearing a tire burst1 or smelling a rotten egg1 or feeling the coldness of a frog4 ,these are events that are 8data0 in the sense of ,chapter ,,xxv2 but1 on the principles explained in that chapter1 we infer that there are events which are not data and happen at a distance from our own body4 ,some of these are data to other people1 others are data to no one4 ,in the case of the flash of lightning1 there is an electro-magnetic disturbance consisting of events travelling outward from the place where the flash takes place1 and then when this disturbance reaches the eye of a person or animal that can see1 there is a percept1 which is causally continuous with the events between the place of the lightning and the body of the percipient4 ,percepts afford the logical premisses for all inferences to events that are not precepts1 wherever such inferences are logically justifiable4 ,particular colours and sounds and so on are events2 their causal antecedents in the inanimate world are also events4 ,if we assume1 as ,i propose to do1 that every event has only a finite number of parts1 then every event is composed of a finite number of events that have no parts4 ,such events ,i shall call 8minimal events40 ,it will simplify our discussion to assume them1 but by a little circumlocution this assumption could be eliminated4 ,the reader must not therefore regard it as an essential part of what follows4 ,a minimal event occupies a finite region in space-time4 ,let us take time alone for purposes of illustration4 ,the event in question may overlap in time with each of two others1 although the first of these others wholly precedes the second2 for example1 you may hear a long note on the violin while you hear two short notes on the piano4 7,it is not necessary to suppose that these are really minimal events2 ,i merely want to illustrate what is meant47 ,i assume that every event is contemporaneous with events that are not contemporaneous with each other2 this is what is meant by saying that every event lasts for a finite time1 as the reader can easily convince himself if he remembers that time is wholly relational4 ,if we look away from the world of physics for a moment1 and confine ourselves to the world of one man's experience1 we can easily define an 8instant0 in his life4 ,it will be a group of events1 all belonging to his experience1 and having the following two properties3 7#a7 any two of the events overlap2 7#b7 no event outside the group overlaps with every member of the group4 ,by a slightly more complicated but essentially similar method1 we can define a point-instant in space-time as a group of events having two properties analogous to those used just now in defining an 8instant0 in one biography4#ac ,thus the 8points0 7or point-instants7 that the mathematician needs are not simple1 but are structures composed of events1 made up for the convenience of the mathematician4 ,there will be many 8points0 of which a given minimal event is a member2 all these together make up the region of space-time occupied by that event4 ,space-time order1 as well as space-time points1 results from the relations between events4 #ac ,see ,the ,analysis of ,matter1 by the present author1 chap4 xxviii4 ,a piece of matter1 like a space-time point1 is to be constructed out of events1 but the construction is considerably more complicated1 and in the end is only an approximation to what the physicist supposes to be really taking place4 ,there are1 at the moment1 two somewhat different views of matter1 one appropriate to the study of atomic structure1 the other to the general theory of relativity as affording an explanation of gravitation4 ,the view appropriate to atomic structure has itself two forms1 one derived from ,heisenberg1 the other from ,de ,broglie and ,schrdinger4 ,these two forms1 it is true1 are mathematically equivalent1 but in words they are very different4 ,heisenberg regards a piece of matter as a centre from which radiations travel outward2 the radiations are supposed really to occur1 but the matter at their centre is reduced to a mere mathematical fiction4 ,the radiations are1 for example1 such as constitute light2 they are all avowedly systems of events1 not changes in the conditions or relations of 8substances40 ,in the ,de ,broglie-,schrdinger system1 matter consists of wave motions4 ,it is not necessary to the theory to postulate anything about these wave-motions except their mathematical characteristics1 but1 obviously1 since they are to explain matters they cannot serve their purpose if they consist of motions of matter4 ,in this system also1 therefore1 we are led to construct matter out of systems of events1 which just happen1 and do not happen 8to0 matter or 8to0 anything else4 ,gravitation1 as explained by the general theory of relativity1 is reduced to 8crinkles0 in space-time4 ,space-time being1 as we have already seen1 a system constructed out of events1 the 8crinkles0 in it are also derived from events4 ,there is no reason to suppose that there is a 8thing0 at the place where the 8crinkle0 is most crinkly4 ,thus in this part of physics1 also1 matter has ceased to be a 8thing0 and has become merely a mathematical characteristic of the relations between complicated logical structures composed of events4 ,it was traditionally a property of substance to be permanent1 and to a considerable extent matter has retained this property in spite of its loss of substantiality4 ,but its permanence now is only approximate1 not absolute4 ,it is thought that an electron and a proton can meet and annihilate each other2 in the stars this is supposed to be happening on a large scale4#ad ,and even while an electron or a proton lasts1 it has a different kind of persistence from that formerly attributed to matter4 ,a wave in the sea persists for a longer or shorter time3 the waves that ,i see dashing themselves to pieces on the ,cornish coast may have come all the way from ,brazil1 but that does not mean that a 8thing0 has travelled across the ,atlantic2 it means only that a certain process of change has travelled4 ,and just as a wave in the sea comes to grief at last on the rocks1 so an electron or a proton may come to grief when it meets some unusual state of affairs4 #ad ,see ,the ,analysis of ,matter1 by the present author1 chap4 xxviii4 ,thus 8matter0 has very definitely come down in the world as a result of recent physics4 ,it used to be the cause of our sensations3 ,dr4 ,johnson 8disproved0 ,berkeley's denial of matter by kicking a stone4 ,if he had known that his foot never touched the stone1 and that both were only complicated systems of wave-motions1 he might have been less satisfied with his refutation4 ,we cannot say that 8matter0 is the cause of our sensations4 ,we can say that the events which cause our sensations usually belong to the sort of group that physicists regard as material2 but that is a very different thing4 ,impenetrability used to be a noble property of matter1 a kind of ,declaration of ,independence2 now it is a merely tautological result of the way in which matter is defined4 ,the events which are the real stuff of the world are not impenetrable1 since they can overlap in space-time4 ,in a word1 8matter0 has become no more than a convenient shorthand for stating certain causal laws concerning events4 ,but if matter has fared badly1 mind has fared little better4 ,the adjective 8mental0 is one which is not capable of any exact significance4 ,there is1 it is true1 an important group of events1 namely percepts1 all of which may be called 8mental04 ,but it would be arbitrary to say that there are no 8mental0 events except percepts1 and yet it is difficult to find any principle by which we can decide what other events should be included4 ,perhaps the most essential characteristics of mind are introspection and memory4 ,but memory in some of its forms is1 as we have seen1 a consequence of the law of conditioned reflexes1 which is at least as much physiological as psychological1 and characterises living tissue rather than mind4 ,knowledge1 as we have found1 is not easy to distinguish from sensitivity1 which is a property possessed by scientific instruments4 ,introspection is a form of knowledge1 but turns out1 on examination1 to be little more than a cautious interpretation of ordinary 8knowledge04 ,where the philosopher's child at the ,zoo says 8,there is a hippopotamus over there01 the philosopher should reply3 8,there is a coloured pattern of a certain shape1 which may perhaps be connected with a system of external causes of the sort called a hippopotamus04 7,i do not live up to this precept myself47 ,in saying that there is a coloured pattern1 the philosopher is practising introspection in the only sense that ,i can attach to that term1 i4e4 his knowledge-reaction is to an event situated in his own brain from the standpoint of physical space1 and is consciously avoiding physiological and other inference as far as possible4 ,events to which a knowledge-reaction of this sort occurs are 8mental02 so are1 presumably1 other events resembling them in certain respects4 ,but ,i do not see any way of defining this wider group except by saying that mental events are events in a living brain1 or1 better1 in a region combining sensitivity and the law of learned reactions to a marked extent4 ,this definition has at least the merit of showing that mentality is an affair of causal laws1 not of the quality of single events1 and also that mentality is a matter of degree4 ,perhaps it is not unnecessary to repeat1 at this point1 that events in the brain are not to be regarded as consisting of motions of bits of matter4 ,matter and motion1 as we have seen1 are logical constructions using events as their material1 and events are therefore something quite different from matter in motion4 ,i take it that1 when we have a percept1 just what we perceive 7if we avoid avoidable sources of error7 is an event occupying part of the region which1 for physics1 is occupied by the brain4 ,in fact1 perception gives us the most concrete knowledge we possess as to the stuff of the physical world1 but what we perceive is part of the stuff of our brains1 not part of the stuff of tables and chairs1 sun1 moon1 and stars4 ,suppose we are looking at a leaf1 and we see a green patch4 ,this patch is not 8out there0 where the leaf is1 but is an event occupying a certain volume in our brains during the time that we see the leaf4 ,seeing the leaf consists of the existence1 in the region occupied by our brain1 of a green patch causally connected with the leaf1 or rather with a series of events emanating from the place in physical space where physics places the leaf4 ,the percept is one of this series of events1 differing from the others in its effects owing to the peculiarities of the region in which it occurs--or perhaps it would be more correct to say that the different effects are the peculiarities of the region4 ,thus 8mind0 and 8mental0 are merely approximate concepts1 giving a convenient shorthand for certain approximate laws4 ,in a completed science1 the word 8mind0 and the word 8matter0 would both disappear1 and would be replaced by causal laws concerning 8events01 the only events known to us otherwise than in their mathematical and causal properties being percepts1 which are events situated in the same region as a brain and having effects of a peculiar sort called 8knowledge-reactions04 ,it will be seen that the view which ,i am advocating is neither materialism nor mentalism1 but what we call 8neutral monism04 ,it is monism in the sense that it regards the world as composed of only one kind of stuff1 namely events2 but it is pluralism in the sense that it admits the existence of a great multiplicity of events1 each minimal event being a logically self-subsistent entity4 ,there is1 however1 another question1 not quite the same as this1 namely the question as to the relations of psychology and physics4 ,if we knew more1 would psychology be absorbed in physics8 or1 conversely1 would physics be absorbed in psychology8 ,a man may be a materialist and yet hold that psychology is an independent science2 this is the view taken by ,dr4 ,broad in his important book on ,the ,mind and its ,place in ,nature4 ,he holds that a mind is a material structure1 but that it has properties which could not1 even theoretically1 be inferred from those of its material constituents4 ,he points out that structures very often have properties which1 in the present state of our knowledge1 cannot be inferred from the properties and relations of their parts4 ,water has many properties which we cannot infer from those of hydrogen and oxygen1 even if we suppose ourselves to know the structure of the molecule of water more completely than we do as yet4 ,properties of a whole which cannot1 even theoretically1 be inferred from the properties and relations of its parts are called by ,dr4 ,broad 8emergent0 properties4 ,thus he holds that a mind 7or brain7 has properties which are 8emergent01 and to this extent psychology will be independent of physics and chemistry4 ,the 8emergent0 properties of minds will only be discoverable by observation of minds1 not by inference from the laws of physics and chemistry4 ,this possibility is an important one1 and it will be worth while to consider it4 ,our decision to regard a unit of matter as itself not ultimate1 but an assemblage of events1 somewhat alters the form of our question as to 8emergent0 properties4 ,we have to ask3 ,is matter emergent from events8 ,is mind emergent from events8 ,if the former1 is mind emergent from matter1 or deducible from the properties of matter1 or neither8 ,if the latter1 is matter emergent from mind or deducible from the properties of mind1 or neither8 ,of course1 if neither mind nor matter is emergent from events1 these latter questions do not arise4 ,let us coin a word1 8chrono-geography01 for the science which begins with events having space-time relations and does not assume at the outset that certain strings of them can be treated as persistent material units or as minds4 ,then we have to ask ourselves first3 can the science of matter1 as it appears in physics and chemistry1 be wholly reduced to chrono-geography8 ,if no1 matter is emergent from events2 if yes1 it is not emergent4 ,is matter emergent from events8 ,in the present state of science it is difficult to give a decided answer to this question4 ,the notion of matter1 in modern physics1 has become absorbed into the notion of energy4 ,eddington1 in his ,mathematical ,theory of ,relativity shows that1 in virtue of the laws assumed concerning events1 there must be something having the observed properties of matter and energy as regards conservation4 ,this he calls the 8material-energy-tensor01 and suggests that it is the reality which we sometimes call 8matter0 and sometimes 8energy04 ,to this extent1 matter has been shown to be not emergent4 ,but the existence of electrons and protons 7to the extent that they do exist7 has not yet been deduced from the general theory of relativity1 though attempts are being made and may at any moment succeed4 ,if and when these attempts succeed1 physics will cease to be in any degree independent of chrono-geography1 but for the present it remains in part independent4 ,as for chemistry1 although we cannot practically reduce it all to physics1 we can see how1 theoretically1 this could be done1 and ,i think it is safe to assume that it is not an ultimately independent science4 ,the question we have been asking is3 could we predict1 theoretically1 from the laws of events that there must be material units obeying the laws which they do in fact obey1 or is this a new1 logically independent1 fact8 ,in theory we might be able to prove that it is not independent1 but it would be very difficult to prove that it is4 ,the present position is1 broadly speaking1 that the continuous properties of the physical world can be deduced from chrono-geography1 but not the discontinuous facts1 viz4 electrons and protons and ,planck's quantum4 ,thus for the present materiality is practically1 though perhaps not theoretically1 an emergent characteristic of certain groups of events4 ,is mind emergent from events8 ,this question1 as yet1 can hardly be even discussed intelligently1 because psychology is not a sufficiently advanced science4 ,there are1 nevertheless1 some points to be noted4 ,chrono-geography is concerned only with the abstract mathematical properties of events1 and cannot conceivably1 unless it is radically transformed1 prove that there are visual events1 or auditory events1 or events of any of the kinds that we know by perception4 ,in this sense1 psychology is certainly emergent from chrono-geography and also from physics1 and it is hard to see how it can ever cease to be so4 ,the reason for this is that our knowledge of data contains features of a qualitative sort1 which cannot be deduced from the merely mathematical features of the space-time events inferred from data1 and yet these abstract mathematical features are all that we can legitimately infer4 ,the above argument decides also that mind must be emergent from matter1 if it is a material structure4 ,no amount of physics can ever tell us all that we do in fact know about our own percepts4 ,we have still to ask whether we are to regard a mind as a structure of material units or not4 ,if we do so regard it1 we are1 so far as mind is concerned1 emergent materialists in view of what we have just decided2 this is the view favoured by ,dr4 ,broad4 ,if we do not so regard it1 we are in no sense materialists4 ,in favour of the materialist view1 there is the fact that1 so far as our experience goes1 minds only emerge in connection with certain physical structures1 namely living bodies1 and that mental development increases with a certain kind of complexity of physical structure4 ,we cannot set against this the argument that minds have peculiar characteristics1 for this is quite consistent with emergent materialism4 ,if we are to refute it1 it must be by finding out what sort of group of events constitutes a mind4 ,it is time to address ourselves to this question4 ,what is a mind8 ,it is obvious1 to begin with1 that a mind must be a group of mental events1 since we have rejected the view that it is a single simple entity such as the ego was formerly supposed to be4 ,our first step1 therefore1 is to be clear as to what we mean by a 8mental0 event4 ,we said a few pages ago that3 ,mental events are events in a region combining sensitivity and the law of learned reactions to a marked extent4 ,for practical purposes1 this means 7subject to a proviso to be explained shortly7 that a mental event is any event in a living brain4 ,we explained that this does not mean that a mental event consists of matter in motion1 which is what an old-fashioned physicist would regard as the sort of event that happens in a brain4 ,matter in motion1 we have seen1 is not an event in our sense1 but a shorthand description of a very complicated causal process among events of a different sort4 ,but we must say a few words in justification of our definition4 ,let us consider some alternative definitions4 ,a mental event1 we might say1 is one which is 8experienced40 ,when is an event 8experienced08 ,we might say3 when it has 8mnemic0 effects1 i4e4 effects governed by the law of association4 ,but we saw that this law applies to purely bodily events such as the contraction of the pupil1 with which nothing 8mental0 seems to be connected4 ,thus if our definition is to serve1 we shall have to define 8experience0 differently2 we shall have to say that the mnemic effects must include something that can be called 8knowledge40 ,this would suggest the definition3 ,a mental event is anything that is remembered4 ,but this is too narrow3 we only remember a small proportion of our mental events4 ,we might have regarded 8consciousness0 as the essence of mental events1 but this view was examined and found inadequate in ,chapter ,,xx4 ,moreover1 we do not want our definition to exclude the 8unconscious04 ,it is clear that the primary mental events1 those about which there can be no question1 are percepts4 ,but percepts have certain peculiar causal properties1 notably that they give rise to knowledge-reactions1 and that they are capable of having mnemic effects which are cognitions4 ,these causal properties1 however1 belong to some events which are not apparently percepts4 ,it seems that any event in the brain may have these properties4 ,and perhaps we were too hasty in saying that the contraction of the pupil on hearing a loud noise involves nothing 8mental04 ,there may be other 8mental0 events connected with a human body besides those belonging to the central personality4 ,i shall come back to this possibility presently4 ,meanwhile1 ,i shall adhere to the above definition of a 8mental0 event1 which1 as we saw1 makes mentality a matter of degree4 ,we can now return to the question3 ,what is a mind8 ,there may be mental events not forming part of the sort of group that we should call a 8mind01 but there certainly are groups having that kind of unity that make us call them one mind4 ,there are two marked characteristics of a mind3 ,first1 it is connected with a certain body2 secondly1 it has the unity of one 8experience04 ,the two prima facie diverge in cases of dual or multiple personality1 but ,i think this is more apparent than real4 ,these two characteristics are1 one physical1 the other psychological4 ,let us consider each in turn as a possible definition of what we mean by one 8mind04 ,in the physical way1 we begin by observing that every mental event known to us is also part of the history of a living body1 and we define a 8mind0 as the group of mental events which form part of the history of a certain living body4 ,the definition of a living body is chemical1 and the reduction of chemistry to physics is clear in theory1 though in practice the mathematics is too difficult4 ,it is so far a merely empirical fact that mnemic causation is almost exclusively associated with matter having a certain chemical structure4 ,but the same may be said of magnetism4 ,as yet1 we cannot deduce the magnetic properties of iron from what we know of the structure of the atom of iron1 but no one doubts that they could be deduced by a person with sufficient knowledge and sufficient mathematical skill4 ,in like manner it may be assumed that mnemic causation is theoretically deducible from the structure of living matter4 ,if we knew enough1 we might be able to infer that some other possible structure would exhibit mnemic phenomena1 perhaps in an even more marked degree2 if so1 we might be able to construct ,robots who would be more intelligent than we are4 ,in the psychological way of defining a 8mind01 it consists of all the mental events connected with a given mental event by 8experience01 i4e4 by mnemic causation1 but this definition needs a little elaboration before it can be regarded as precise4 ,we do not want the contraction of the pupil to count as a 8mental0 event2 therefore a mental event will have to be one which has mnemic effects1 not merely mnemic causes4 ,in that case1 however1 there cannot be a last mental event in a man's life1 unless we assume that it may have mnemic effects on his body after death4 ,perhaps we may avoid this inconvenience by discovering the kind of event that usually has mnemic effects1 though they may be prevented from occurring by special circumstances4 ,or we might maintain that death is gradual1 even when it is what is called instantaneous2 in that case the last events in a man's life grow progressively less mental as life ebbs4 ,neglecting this point1 which is not very important1 we shall define the 8experience0 to which a given mental event belongs as all those mental events which can be reached from the given event by a mnemic causal chain1 which may go backwards or forwards1 or alternately first one and then the other4 ,this may be conceived on the analogy of an engine shunting at a junction or where there are many points3 any line that can be reached1 by however many shuntings1 will count as part of the same experience4 ,we cannot be sure that all the mental events connected with one body are connected by links of mnemic causation with each other1 and therefore we cannot be sure that our two definitions of one 8mind0 give the same result4 ,in cases of multiple personality1 some at least of the usual mnemic effects1 notably recollection1 are absent in the life of one personality when they have occurred in the life of the other4 ,but probably both personalities are connected by mnemic chains with events which occurred before the dissociation took place1 so that there would be only one mind according to our definition4 ,but there are other possibilities which must be considered4 ,it may be that each cell in the body has its own mental life1 and that only selections from these mental lives go to make up the life which we regard as ours4 ,the 8unconscious0 might be the mental lives of subordinate parts of the body1 having occasional mnemic effects which we can notice1 but in the main separate from the life of which we are 8conscious04 ,if so1 the mental events connected with one body will be more numerous than the events making up its central 8mind04 ,these1 however1 are only speculative possibilities4 ,i spoke a moment ago of the life of which we are 8conscious01 and perhaps the reader has been wondering why ,i have not made more use of the notion of 8consciousness04 ,the reason is that ,i regard it as only one kind of mnemic effect1 and not one entitled to a special place4 ,to say that ,i am 8conscious0 of an event is to say that ,i recollect it1 at any rate for a short time after it has happened4 ,to say that ,i recollect an event is to say that a certain event is occurring in me now which is connected by mnemic causation with the event recollected1 and is of the sort that we call a 8cognition0 of that event4 ,but events which ,i do not recollect may have mnemic effects upon me4 ,this is the case1 not only where we have ,freudian suppression1 but in all habits which were learnt long ago and have now become automatic1 such as writing and speaking4 ,the emphasis upon consciousness has made a mystery of the 8unconscious01 which ought to be in no way surprising4 ,it does not much matter which of our two definitions of a 8mind0 we adopt4 ,let us1 provisionally1 adopt the first definition1 so that a mind is all the mental events which form part of the history of a certain living body1 or perhaps we should rather say a living brain4 ,we can now tackle the question which is to decide whether we are emergent materialists or not1 namely3 ,is a mind a structure of material units8 ,i think it is clear that the answer to this question is in the negative4 ,even if a mind consists of all the events in a brain1 it does not consist of bundles of these events grouped as physics groups them1 i4e4 it does not lump together all the events that make up one piece of matter in the brain1 and then all the events that make up another1 and so on4 ,mnemic causation is what concerns us most in studying mind1 but this seems to demand a recourse to physics1 if we assume1 as seems plausible1 that mental mnemic causation is due to effects upon the brain4 ,this question1 however1 is still an open one4 ,if mnemic causation is ultimate1 mind is emergent4 ,if not1 the question is more difficult4 ,as we saw earlier1 there certainly is knowledge in psychology which cannot ever form part of physics4 ,but as this point is important1 ,i shall repeat the argument in different terms4 ,the difference between physics and psychology is analogous to that between a postman's knowledge of letters and the knowledge of a recipient of letters4 ,the postman knows the movements of many letters1 the recipient knows the contents of a few4 ,we may regard the light and sound waves that go about the world as letters of which the physicist may know the destination2 some few of them are addressed to human beings1 and when read give psychological knowledge4 ,of course the analogy is not perfect1 because the letters with which the physicist deals are continually changing during their journeys1 as if they were written in fading ink1 which1 also1 was not quite dry all the time1 but occasionally got smudged with rain4 ,however1 the analogy may pass if not pressed4 ,it would be possible without altering the detail of previous discussions1 except that of ,chapter ,,xxv1 to give a different turn to the argument1 and make matter a structure composed of mental units4 ,i am not quite sure that this is the wrong view4 ,it arises not unnaturally from the argument as to data contained in ,chapter ,,xxv4 ,we saw that all data are mental events in the narrowest and strictest sense1 since they are percepts4 ,consequently all verification of causal laws consists in the occurrence of expected percepts4 ,consequently any inference beyond percepts 7actual or possible7 is incapable of being empirically tested4 ,we shall therefore be prudent if we regard the non-mental events of physics as mere auxiliary concepts1 not assumed to have any reality1 but only introduced to simplify the laws of percepts4 ,thus matter will be a construction built out of percepts1 and our metaphysic will be essentially that of ,berkeley4 ,if there are no non-mental events1 causal laws will be very odd2 for example1 a hidden dictaphone may record a conversation although it did not exist at the time1 since no one was perceiving it4 ,but although this seems odd1 it is not logically impossible4 ,and it must be conceded that it enables us to interpret physics with a smaller amount of dubious inductive and analogical inference than is required if we admit non-mental events4 ,in spite of the logical merits of this view1 ,i cannot bring myself to accept it1 though ,i am not sure that my reasons for disliking it are any better than ,dr4 ,johnson's4 ,i find myself constitutionally incapable of believing that the sun would not exist on a day when he was everywhere hidden by clouds1 or that the meat in a pie springs into existence at the moment when the pie is opened4 ,i know the logical answer to such objections1 and qua logician ,i think the answer a good one4 ,the logical argument1 however1 does not even tend to show that there are not non-mental events2 it only tends to show that we have no right to feel sure of their existence4 ,for my part1 ,i find myself in fact believing in them in spite of all that can be said to persuade me that ,i ought to feel doubtful4 ,there is an argument1 of a sort1 against the view we are considering4 ,i have been assuming that we admit the existence of other people and their perceptions1 but question only the inference from perceptions to events of a different kind4 ,now there is no good reason why we should not carry our logical caution a step further4 ,i cannot verify a theory by means of another man's perceptions1 but only by means of my own4 ,therefore the laws of physics can only be verified by me in so far as they lead to predictions of my percepts4 ,if then1 ,i refuse to admit non-mental events because they are not verifiable1 ,i ought to refuse to admit mental events in every one except myself1 on the same ground4 ,thus ,i am reduced to what is called 8solipsism01 i4e4 the theory that ,i alone exist4 ,this is a view which is hard to refute1 but still harder to believe4 ,i once received a letter from a philosopher who professed to be a solipsist1 but was surprised that there were no others6 ,yet this philosopher was by way of believing that no one else existed4 ,this shows that solipsism is not really believed even by those who think they are convinced of its truth4 ,we may go a step further4 ,the past can only be verified indirectly1 by means of its effects in the future2 therefore the type of logical caution we have been considering should lead us to abstain from asserting that the past really occurred3 we ought to regard it as consisting of auxiliary concepts convenient in stating the laws applicable to the future4 ,and since the future1 though verifiable if and when it occurs1 is as yet unverified1 we ought to suspend judgment about the future also4 ,if we are not willing to go so far as this1 there seems no reason to draw the line at the precise point where it was drawn by ,berkeley4 ,on these grounds ,i feel no shame in admitting the existence of non-mental events such as the laws of physics lead us to infer4 ,nevertheless1 it is important to realise that other views are tenable4 ,,chapter ,,xxvii ,,man',s ,,place ,,in ,,the ,,universe ,in this final chapter1 ,i propose to recapitulate the main conclusions at which we have arrived1 and then to say a few words on the subject of ,man's relation to the universe in so far as philosophy has anything to teach on this subject without extraneous help4 ,popular metaphysics divides the known world into mind and matter1 and a human being into soul and body4 ,some--the materialists--have said that matter alone is real and mind is an illusion4 ,many--the idealists in the technical sense1 or mentalists1 as ,dr4 ,broad more appropriately calls them--have taken the opposite view1 that mind alone is real and matter is an illusion4 ,the view which ,i have suggested is that both mind and matter are structures composed of a more primitive stuff which is neither mental nor material4 ,this view1 called 8neutral monism01 is suggested in ,mach's ,analysis of ,sensations1 developed in ,william ,james's ,essays in ,radical ,empiricism1 and advocated by ,john ,dewey1 as well as by ,professor ,r4 ,b4 ,parry and other ,american realists4 ,the use of the word 8neutral0 in this way is due to ,dr4 ,h4 ,m4 ,sheffer1#ae formerly of ,harvard1 who is one of the ablest logicians of our time4 #ae ,see ,holt's ,concept of ,consciousness1 preface4 ,since man is the instrument of his own knowledge1 it is necessary to study him as an instrument before we can appraise the value of what our senses seem to tell us concerning the world4 ,in ,part ,i we studied man1 within the framework of common-sense beliefs1 just as we might study clocks or thermometers1 as an instrument sensitive to certain features of the environment1 since sensitiveness to the environment is obviously an indispensable condition for knowledge about it4 ,in ,part ,,ii we advanced to the study of the physical world4 ,we found that matter1 in modern science1 has lost its solidity and substantiality2 it has become a mere ghost haunting the scenes of its former splendours4 ,in pursuit of something that could be treated as substantial1 physicists analysed ordinary matter into molecules1 molecules into atoms1 atoms into electrons and protons4 ,there1 for a few years1 analysis found a resting-place4 ,but now electrons and protons themselves are dissolved into systems of radiations by ,heisenberg1 and into systems of waves by ,schrdinger--the two theories amount mathematically to much the same thing4 ,and these are not wild metaphysical speculations2 they are sober mathematical calculations1 accepted by the great majority of experts4 ,another department of theoretical physics1 the theory of relativity1 has philosophical consequences which are1 if possible1 even more important4 ,the substitution of space-time for space and time has made the category of substance less applicable than formerly1 since the essence of substance was persistence through time1 and there is now no one cosmic time4 ,the result of this is to turn the physical world into a four-dimensional continuum of events1 instead of a series of three-dimensional states of a world composed of persistent bits of matter4 ,a second important feature of relativity-theory is the abolition of force1 particularly gravitational force1 and the substitution of differential causal laws having to do only with the neighbourhood of an event1 not with an influence exerted from a distance1 such as gravitation formerly seemed to be4 ,the modern study of the atom has had two consequences which have considerably changed the philosophical hearing of physics4 ,on the one hand1 it appears that there are discontinuous changes in nature1 occasions when there is a sudden jump from one state to another without passing through the intermediate states4 7,schrdinger1 it is true1 questions the need for assuming discontinuity2 but so far his opinion has not prevailed47 ,on the other hand1 the course of nature is not so definitely determined by the physical laws at present known as it was formerly thought to be4 ,we cannot predict when a discontinuous change will take place in a given atom1 though we can predict statistical averages4 ,it can no longer be said that1 given the laws of physics and the relevant facts about the environment1 the future history of an atom can theoretically be calculated from its present condition4 ,it may be that this is merely due to the insufficiency of our knowledge1 but we cannot be sure that this is the case4 ,as things stand at present1 the physical world is not so rigidly deterministic as it has been believed to be during the last #bej years4 ,and in various directions what formerly appeared as laws governing each separate atom are now found to be only averages attributable in part to the laws of chance4 ,from these questions concerning the physical world in itself1 we were led to others concerning the causation of our perceptions1 which are the data upon which our scientific knowledge of physics is based4 ,we saw that a long causal chain always intervenes between an external event and the event in us which we regard as perception of the external event4 ,we cannot therefore suppose that the external event is exactly what we see or hear2 it can1 at best1 resemble the percept only in certain structural respects4 ,this fact has caused considerable confusion in philosophy1 partly because philosophers tried to think better of perception than it deserves1 partly because they failed to have clear ideas on the subject of space4 ,it is customary to treat space as a characteristic of matter as opposed to mind1 but this is only true of physical space4 ,there is also perceptual space1 which is that in which what we know immediately through the senses is situated4 ,this space cannot be identified with that of physics4 ,from the standpoint of physical space1 all our percepts are in our heads2 but in perceptual space our percept of our hand is outside our percept of our head4 ,the failure to keep physical and perceptual space distinct has been a source of great confusion in philosophy4 ,in ,part ,,iii we resumed the study of man1 but now as he appears to himself1 not only as he is known to an external observer4 ,we decided1 contrary to the view of the behaviourists1 that there are important facts which cannot be known except when the observer and observed are the same person4 ,the datum in perception1 we decided1 is a private fact which can only be known directly to the percipient2 it is a datum for physics and psychology equally1 and must be regarded as both physical and mental4 ,we decided later that there are inductive grounds1 giving probability but not certainty1 in favour of the view that perceptions are causally connected with events which the percipient does not experience1 which may belong only to the physical world4 ,the behaviour of human beings is distinguished from that of inanimate matter by what are called 8mnemic0 phenomena1 i4e4 by a certain kind of effect of past occurrences4 ,this kind of effects is exemplified in memory1 in learning1 in the intelligent use of words1 and in every kind of knowledge4 ,but we cannot1 on this ground1 erect an absolute barrier between mind and matter4 ,in the first place1 inanimate matter1 to some slight extent1 shows analogous behaviour--e4g4 if you unroll a roll of paper1 it will roll itself up again4 ,in the second place1 we find that living bodies display mnemic phenomena to exactly the same extent to which minds display them4 ,in the third place1 if we are to avoid what ,i have called 8mnemic0 causation1 which involves action at a distance in time1 we must say that mnemic phenomena in mental events are due to the modification of the body by past events4 ,that is to say1 the set of events which constitutes one man's experience is not causally self-sufficient1 but is dependent upon causal laws involving events which he cannot experience4 ,on the other hand1 our knowledge of the physical world is purely abstract3 we know certain logical characteristics of its structure1 but nothing of its intrinsic character4 ,there is nothing in physics to prove that the intrinsic character of the physical world differs1 in this or that respect1 from that of the mental world4 ,thus from both ends1 both by the analysis of physics and by the analysis of psychology1 we find that mental and physical events form one causal whole1 which is not known to consist of two different sorts4 ,at present1 we know the laws of the physical world better than those of the mental world1 but that may change4 ,we know the intrinsic character of the mental world to some extent1 but we know absolutely nothing of the intrinsic character of the physical world4 ,and in view of the nature of the inferences upon which our knowledge of physics rests1 it seems scarcely possible that we should ever know more than abstract laws about matter4 ,in ,part ,,iv we considered what philosophy has to say about the universe4 ,the function of philosophy1 according to the view advocated in this volume1 is somewhat different from that which has been assigned to it by a large and influential school4 ,take1 e4g4 ,kant's antinomies4 ,he argues 7#a7 that space must be infinite1 7#b7 that space cannot be infinite2 and he deduces that space is subjective4 ,the non-,euclideans refuted the argument that it must be infinite1 and ,georg ,cantor refuted the argument that it cannot be4 ,formerly1 a priori logic was used to prove that various hypotheses which looked possible were impossible1 leaving only one possibility1 which philosophy therefore pronounced true4 ,now a priori logic is used to prove the exact contrary1 namely1 that hypotheses which looked impossible are possible4 ,whereas logic was formerly counsel for the prosecution1 it is now counsel for the defence4 ,the result is that many more hypotheses are at large than was formerly the case4 ,formerly1 to revert to the instance of space1 it appeared that experience left only one kind of space to logic1 and logic showed this one kind to be impossible4 ,now1 logic presents many kinds of space as possible apart from experience1 and experience only partially decides between them4 ,thus1 while our knowledge of what is has become less than it was formerly supposed to be1 our knowledge of what may be is enormously increased4 ,instead of being shut in within narrow walls1 of which every nook and cranny could be explored1 we find ourselves in an open world of free possibilities1 where much remains unknown because there is so much to know4 ,the attempt to prescribe to the universe by means of a priori principles has broken down2 logic1 instead of being1 as formerly1 a bar to possibilities1 has become the great liberator of the imagination1 presenting innumerable alternatives which are closed to unreflective common sense1 and leaving to experience the task of deciding1 where decision is possible1 between the many worlds which logic offers for our choice4 ,philosophical knowledge1 if what we have been saying is correct1 does not differ essentially from scientific knowledge2 there is no special source of wisdom which is open to philosophy but not to science1 and the results obtained by philosophy are not radically different from those reached in science4 ,philosophy is distinguished from science only by being more critical and more general4 ,but when ,i say that philosophy is critical1 ,i do not mean that it attempts to criticise knowledge from outside1 for that would be impossible3 ,i mean only that it examines the various parts of our supposed knowledge to see whether they are mutually consistent and whether the inferences employed are such as seem valid to a careful scrutiny4 ,the criticism aimed at is not that which1 without reason1 determines to reject1 but that which considers each piece of apparent knowledge on its merits and retains whatever still appears to be knowledge when this consideration is completed4 ,that some risk of error remains must be admitted1 since human beings are fallible4 ,philosophy may claim justly that it diminishes the risk of error1 and that in some cases it renders the risk so small as to be practically negligible4 ,to do more than this is not possible in a world where mistakes must occur2 and more than this no prudent advocate of philosophy would claim to have performed4 ,i want to end with a few words about man's place in the universe4 ,it has been customary to demand of a philosopher that he should show that the world is good in certain respects4 ,i cannot admit any duty of this sort4 ,one might as well demand of an accountant that he should show a satisfactory balance sheet4 ,it is just as bad to be fraudulently optimistic in philosophy as in money matters4 ,if the world is good1 by all means let us know it2 but if not1 let us know that4 ,in any case1 the question of the goodness or badness of the world is one for science rather than for philosophy4 ,we shall call the world good if it has certain characteristics that we desire4 ,in the past philosophy professed to be able to prove that the world had such characteristics1 but it is now fairly evident that the proofs were invalid4 ,it does not1 of course1 follow that the world does not have the characteristics in question2 it follows only that philosophy cannot decide the problem4 ,take for example the problem of personal immortality4 ,you may believe this on the ground of revealed religion1 but that is a ground which lies outside philosophy4 ,you may believe it on the ground of the phenomena investigated by psychical research1 but that is science1 not philosophy4 ,in former days1 you could believe it on a philosophical ground1 namely1 that the soul is a substance and all substances are indestructible4 ,you will find this argument1 sometimes more or less disguised1 in many philosophers4 ,but the notion of substance1 in the sense of a permanent entity with changing states1 is no longer applicable to the world4 ,it may happen1 as with the electron1 that a string of events are so interconnected causally that it is practically convenient to regard them as forming one entity1 but where this happens it is a scientific fact1 not a metaphysical necessity4 ,the whole question of personal immortality1 therefore lies outside philosophy1 and it is to be decided1 if at all1 either by science or by revealed religion4 ,i will take up another matter in regard to which what ,i have said may have been disappointing to some readers4 ,it is sometimes thought that philosophy ought to aim at encouraging a good life4 ,now1 of course1 ,i admit that it should have this effect1 but ,i do not admit that it should have this as a conscious purpose4 ,to begin with1 when we embark upon the study of philosophy we ought not to assume that we already know for certain what the good life is2 philosophy may conceivably modify our views as to what is good1 in which case it will seem to the non-philosophical to have had a bad moral effect4 ,that1 however1 is a secondary point4 ,the essential thing is that philosophy is part of the pursuit of knowledge1 and that we cannot limit this pursuit by insisting that the knowledge obtained shall be such as we should have thought edifying before we obtained it4 ,i think it could be maintained with truth that all knowledge is edifying1 provided we have a right conception of edification4 ,when this appears to be not the case it is because we have moral standards based upon ignorance4 ,it may happen by good fortune that a moral standard based upon ignorance is right1 but if so knowledge will not destroy it2 if knowledge can destroy it1 it must be wrong4 ,the conscious purpose of philosophy1 therefore1 ought to be solely to understand the world as well as possible1 not to establish this or that proposition which is thought morally desirable4 ,those who embark upon philosophy must be prepared to question all their preconceptions1 ethical as well as scientific2 if they have a determination never to surrender certain philosophic beliefs1 they are not in the frame of mind in which philosophy can be profitably pursued4 ,but although philosophy ought not to have a moral purpose1 it ought to have certain good moral effects4 ,any disinterested pursuit of knowledge teaches us the limits of our power1 which is salutary2 at the same time1 in proportion as we succeed in achieving knowledge1 it teaches the limits of our impotence1 which is equally desirable4 ,and philosophical knowledge1 or rather philosophical thought1 has certain special merits not belonging in an equal degree to other intellectual pursuits4 ,by its generality it enables us to see human passions in their just proportions1 and to realise the absurdity of many quarrels between individuals1 classes1 and nations4 ,philosophy comes as near as possible for human beings to that large1 impartial contemplation of the universe as a whole which raises us for the moment above our purely personal destiny4 ,there is a certain asceticism of the intellect which is good as a part of life1 though it cannot be the whole so long as we have to remain animals engaged in the struggle for existence4 ,the asceticism of the intellect requires that1 while we are engaged in the pursuit of knowledge1 we shall repress all other desires for the sake of the desire to know4 ,while we are philosophising1 the wish to prove that the world is good1 or that the dogmas of this or that sect are true1 must count as weaknesses of the flesh--they are temptations to be thrust on one side4 ,but we obtain in return something of the joy which the mystic experiences in harmony with the will of ,god4 ,this joy philosophy can give1 but only to those who are willing to follow it to the end1 through all its arduous uncertainties4 ,the world presented for our belief by a philosophy based upon modern science is in many ways less alien to ourselves than the world of matter as conceived in former centuries4 ,the events that happen in our minds are part of the course of nature1 and we do not know that the events which happen elsewhere are of a totally different kind4 ,the physical world1 so far as science can show at present1 is perhaps less rigidly determined by causal laws than it was thought to be2 one might1 more or less fancifully1 attribute even to the atom a kind of limited free will4 ,there is no need to think of ourselves as powerless and small in the grip of vast cosmic forces4 ,all measurement is conventional1 and it would be possible to devise a perfectly serviceable system of measurement according to which a man would be larger than the sun4 ,no doubt there are limits to our power1 and it is good that we should recognise the fact4 ,but we cannot say what the limits are1 except in a quite abstract way1 such as that we cannot create energy4 ,from the point of view of human life1 it is not important to be able to create energy2 what is important is to be able to direct energy into this or that channel1 and this can do more and more as our knowledge of science increases4 ,since men first began to think1 the forces of nature have oppressed them2 earthquakes1 floods1 pestilences1 and famines have filled them with terror4 ,now at last1 thanks to science1 mankind is discovering how to avoid much of the suffering that such events have hitherto entailed4 ,the mood in which1 as it seems to me the modern man should face the universe is one of quiet self-respect4 ,the universe as known to science is not in itself either friendly or hostile to man1 but it can be made to act as a friend if approached with patient knowledge4 ,where the universe is concerned1 knowledge is the one thing needful4 ,man1 alone of living things1 has shown himself capable of the knowledge required to give him a certain mastery over his environment4 ,the dangers to man in the future1 or at least in any measurable future1 come1 not from nature1 but from man himself4 ,will he use his power wisely8 ,or will he turn the energy liberated from the struggle with nature into struggles with his fellow-men8 ,history1 science1 and philosophy all make us aware of the great collective achievements of mankind4 ,it would be well if every civilised human being had a sense of these achievements and a realisation of the possibility of greater things to come1 with the indifference which must result as regards the petty squabbles upon which the passions of individuals and nations are wastefully squandered4 ,philosophy should make us know the ends of life1 and the elements in life that have value on their own account4 ,however our freedom may be limited in the causal sphere1 we need admit no limitations to our freedom in the sphere of values3 what we judge good on its own account we may continue to judge good1 without regard to anything but our own feeling4 ,philosophy cannot itself determine the ends of life1 but it can free us from the tyranny of prejudice and from distortions due to a narrow view4 ,love1 beauty1 knowledge1 and joy of life3 these things retain their lustre however wide our purview4 ,and if philosophy can help us to feel the value of these things1 it will have played its parts in man's collective work of bringing light into a world of darkness4 ,,index ther or empty space1 #ajg ,analogy1 positive and negative1 #bga ,analysis of ,sensations 7,mach71 #bib ,animal ,intelligence 7,thorndike71 #cj ,animal learning1 study of1 #bi ff4 ,thorndike's laws of1 #ca f4 learned reactions1 #ce f4 ,a priori1 causation not regarded as1 #aej knowledge1 #bdi f41 #bfe probability1 on ,keynes's theory1 is1 #bgd logic1 #bif ,aristotle1 #bbf ,association1 principle of1 #cc f41 #dh1 #fd1 #ahj ,aston1 ,dr4 ,f4 ,w41 #ii ,atom1 theory of the1 #ih ff4 centre from which radiations travel1 #aeg philosophical consequences of modern study of the1 #bic ,attention1 #bje ,bacon1 #hj ,behaviourism1 its view of man1 #gj ff4 where it breaks down as a final philosophy1 #abi dilemma put to1 #acc its propositions as to thought examined1 #afi ff4 and logic1 #bfc ,behaviourism 7,watson71 #bb1 #ca1 #cc 8,belief01 #bed1 #beh ff4 definition of1 #bfa ,beliefs1 defects in common1 #c ff4 ,bergson1 #ga1 #gc1 #aih ,berkeley1 #bdf f4 ,bodily ,changes in ,pain1 ,hunger1 ,fear and ,rage 7,cannon71 #bah ,body1 human1 #be1 #aci ,bohr1 ,niels1 his addition to the theory of atoms1 #aja ff4 ,bradley1 monistic view of1 #bea criticism of his argument against relations1 #beb ,braithwaite1 ,r4 ,b41 #bfi ,brentano1 #bjb ,broad1 ,dr41 #ahh1 #aie1 #bhb1 #bib ,buddha1 #bbg ,butler1 ,samuel1 #ga ,cannon1 #bah ,cantor1 ,georg1 #bif ,casuistry1 #bbe ,causation1 as an a priori belief1 #e1 #aej notion of 8necessary0 sequence1 #aae conception of1 in science1 #add ff4 8,cause01 ,kant's category of1 #bdh f4 8,chrono-geography01 #bhc ,cognition1 #fa1 #bjb f41 #bag ,conation1 #bjb ,conception1 #bjc 8,conditioned reflexes01 #ce ,confucius1 #bbg ,conscience1 #bbh 8,consciousness01 #fj ,william ,james's views on1 #baj two different meanings of the word1 #baj criticism of common sense view of1 #baa ff4 self1 #bad ,william ,james's views approved1 #bag one kind of mnemic effect1 #bhh ,continuity in nature1 #ajh ,correlation1 laws of1 #aag ,critique of ,practical ,reason 7,kant71 #bdi ,curiosity1 #bbj ,dalton1 #ih 8,data01 #bff f41 #bgf ,de ,broglie1 #bgh ,decalogue1 the1 #bbg ,descartes1 #i1 #afb ff41 #bcg ff4 ,desire1 behaviourist view of1 #ij f4 introspective view of1 #bba ff4 ,dewey1 ,john1 #bib ,discontinuity in nature1 #aja1 #ajf1 #ajh ,dreams1 #fb1 #abg1 #age1 #agf1 #ahe1 #ahi1 #aic ,dualism of mind and matter1 #ada1 #bci ,ductless glands1 the1 #bah ,eddington1 ,professor1 #bgc1 #bgi ,education1 #bcc ,einstein1 #if1 #aaf1 #bci1 #bdb1 #bdi ,electron1 #ii ff41 #aah1 #ade 8,emergent0 properties1 #bhb ,emotions1 essential physiological conditions of the1 #aah subject to 8,conditioning01 #aai generate irrational opinions1 #abj ,energy1 radiation of1 from matter into empty space1 #ade propagation in empty space1 #ade impact on matter in empty space1 #adf ,essays in ,radical ,empiricism 7,william ,james71 #baj1 #bib ,ethics1 views of the ancients on1 #bbg theory that virtue consists in obedience to authority1 #bbg ff4 utilitarian theory of1 #bbi f4 the concept of 8good01 #bcj mainly social1 #bcc the supreme moral rule1 #bcd f4 ,events1 in physics1 #aaj f4 string of1 #aah f4 8mental01 #ada1 #bhj ff4 structure and mathematical laws of1 #aeg minimal1 #bgg matter constructed out of1 #bgh ,experience1 effects of1 in a reaction to stimulus1 #ahj ff4 ,familiarity1 a stage in memory1 #aie f4 ,fear and ,rage1 #bai ,feeling1 as mental occurrence1 #bjb ,forces1 #aaa1 #aad1 #aag1 #abj f4 ,form1 reaction to1 #he f4 ,freudian 8unconscious0 the1 #bba ,galileo1 #hj ,generalisations1 #bga f4 ,geodesic1 #aab1 #aag ,geometry1 as empirical as geography1 #bdi f4 ,gestaltpsychologie1 #cg1 #da1 #dc1 #fh1 #bdg ,gravitation1 #aaf f41 #ade1 #bgi ,griffith1 ,mr4 ,percy1 #aah ,habit-formation1 #cf ,habit-memory1 #ahh1 #aif ,hegel1 #bbg1 #bbi1 #bea ,heisenberg1 #if1 #aje1 #bgh1 #bic ,heisenberg-,schrdinger theories of atomic structure1 #bdc ,heraclitus1 #bea ,huc1 ,monsieur1 #bcb ,hume1 #ahj1 #aia1 #bdg f4 ,images1 visual1 auditory and tactual1 #agf behaviourist explanation of1 #agg f4 difference between sensations and1 #agi ff4 definition of1 #ahd f4 first stage in memory1 #aie ,imagination1 analysis of1 #aij ff4 essence of1 #aia exceptional gifts of1 #aic and belief1 #aic f4 difference between memory and1 #aid ,induction problem of validity of1 #ad as a practice1 #hj f4 principle of1 #bfh f4 logical problem of1 #bfi ff4 ,mr4 ,keynes's examination of1 #bgj ff4 ,inference1 8physiological01 #ac1 #hj ff41 #ace syllogistic1 #gi inductive and mathematical1 #hc ff4 8,innate ideas01 doctrine of1 #bde ,interval1 space-like and time-like1 #aaj f4 ,introspection1 #aj1 #aa1 #ab1 #agb f41 #bja ff4 ,james1 ,william1 #baj1 #bbc4 ,kant1 #hj1 #bja1 #bci1 #bdh1 #bif ,keynes ,mr41 on problems of induction1 #bfi ff4 ,khler1 #cg ff4 ,knowing1 as mental occurrence1 #bjb ,knowledge1 as displayed in reactions to environment1 #ag ff4 perceptual1 #eh ff4 behaviourist view of1 #hh ff4 difference between introspective and other1 #bae a priori1 #bdi f4 limitations on1 imposed by structure of language1 #bfd f4 ,knowledge-reaction1 #baf1 #bhb ,language1 as a bodily habit1 #dc ff4 psychological side of1 #dh words in an ideal logical1 #bef f4 and things1 relation between1 #bfd ,laws1 causal1 #add ff4 evidence for1 #adg universal characteristics of1 #adi ,learning1 laws of1 #bc1 #bi ff4 two ways of1 #ci in infants1 #da1 #dh by increase of sensitivity1 #ie f4 ,leibniz1 #bci1 #bda f4 ,le ,problme logique de l'induction 7,jean ,nicod71 #bfi1 #bgc ,locke1 #bdd ff4 ,logic1 #bfc1 #bif 8,logical atomism01 #bdh ,mach1 #bad1 #bib ,man1 his relation to the ,universe1 #bib1 #bie1 #bih ff4 ,materialism1 as a philosophy1 #aei ,mathematical ,theory of ,relativity 7,eddington71 #bhc ,matter1 the structure of the atom1 #ih ff4 essence of1 #adf f4 as conceived in modern physics1 #aeg1 #bic old view of1 now untenable1 #aeh ff4 constructed out of events1 #bgh permanence of1 only approximate1 #bgi possibly a structure of mental units1 #bij ,maxwell's equations1 #ajg1 #ade ,meaning1 #eb1 #ga1 #hb ,meinong1 #bjb ,memory1 behaviourist theory of1 #ga ff4 its reference to the past1 #ahh ff4 feeling of pastness complex1 #aij more fundamental than imagination1 #aij vital difference between imagination and1 #aid ,dr4 ,broad's view on reference to the past1 #aie stages of1 #aie ff4 immediate1 #aif f4 true recollection1 #aig ff4 trustworthiness of1 #aii ,memory and testimony1 #e ff4 ,mendeleev1 #ii 8,mental0 events1 #aad1 #ada f41 #bhj f4 8,mental0 occurrences1 #bja1 #bab ,mentality of ,apes 7,khler71 #cg ff41 #fb ,mill1 ,j4 ,s41 his canons of induction1 #bfi f4 ,mind and matter1 conventional notions of1 #ada distinction between1 illusory1 #adb1 #bja gap between1 how filled in1 #adh interaction between1 #aej theory of 8neutral monism01 #bjf ff4 ,cartesian dualism1 #bci ,leibniz's theory of1 #bda ,mind1 a cross-section in a stream of physical causation1 #aej modern conception of1 #bhj ff4 emergent from events1 #bhd definitions of a1 #bhe ff4 ,minkowski1 #bci ,mneme 7,semon71 #di 8,mnemic0 effects1 #di1 #bji1 #bie 8,mnemic0 occurrences1 #di1 #ahj f4 ,monads1 #bda ,monists and pluralists1 controversy between1 #bea ff4 pluralism the view of science and common sense1 #bec ,moore1 ,dr4 ,g4 ,e41 on notion of 8good01 #bcj 8,moral issues01 #bbg ,motion1 #aai1 #afc ,mystics1 #bbi1 #bfd1 #cjj ,names1 #ec ,necessity1 anthropomorphic notion of1 #aae1 #aag 8,neutral monism01 theory of1 #bjf ff41 #baj1 #bhb1 #bib ,newton1 #bdb ,nisbet1 ,r4 ,h41 on probability1 #bge ,object1 what happens when we see an1 #adf f4 ,objective and subjective study1 #cj ,objectivity1 #aed f41 #afi ,ogden and ,richards1 ,messrs41 #eb ,parmenides1 monistic view complete in1 #bea ,parry1 ,professor ,r4 ,b41 #bib ,perception1 difference between introspection and1 #aj f4 a species of sensitivity1 #ei1 #abc and inference1 #fe f4 from objective standpoint1 #ff ff4 of external event1 analysis of1 #abc ff4 element of subjectivity in1 #acj ff4 and causal laws of physics1 #ade ff4 its relation to the object causal and mathematical1 #adi from introspective standpoint1 #bja ff4 ,perceptive knowledge1 stages in act of1 #ah ff4 ,percepts1 #acc1 #ace1 #acg ff4 ,perspective1 #aeb ,philosophy1 the business of1 #b1 #bcf ,behaviourism as a1 #abi ff4 ,utilitarian1 #bbi f4 systems of ,descartes1 ,spinoza1 and ,leibniz1 #bcg ff4 ,locke1 ,berkeley1 and ,hume1 #bdd ff4 conscious purpose of1 #bii ,physics1 modern1 #ig causal laws in1 #aad ff41 #ade ff4 and perception1 #abc ff4 spatial relations in1 #acg ff4 our knowledge of1 #aea ff4 only mathematical properties of1 discoverable1 #aeg less deterministic than formerly1 #bci and psychology1 #bhb1 #bhi ,pictures1 as representations1 #ahc 8,planck's ,constant01 #aja f4 ,plato1 #bbf ,poetry1 #bbj ,probability1 fundamental in science1 #bgd a priori on ,mr4 ,keynes's theory1 #bgd 8frequency01 theory of1 #bgd f4 ,psychology1 #af1 #agb1 #ahd and physics1 #bhb1 #bhi 8,psychophysical parallelism01 #bch 8,public good01 the1 #bcj ,publicity1 in the case of physical phenomena1 #agj ,quantum changes1 #ajf ,radio-activity1 #ii1 #ajc ,reactions1 learned1 #ba1 #cc1 #ce1 #cf1 #di1 #ha ,realism1 naive1 #age ,recognition1 two forms of1 #aif ,recollection1 true1 #aig ff4 ,relations1 ,bradley's argument against1 #beb cause of confusion about1 #bfd ,relativity1 theory of1 8space-time0 instead of one cosmic time and space1 #ajh some results of the1 #ajh ff4 8events0 instead of bodies moving1 #aaj relations between 8events01 #aaj f4 no 8forces0 in the1 #aaa philosophical consequences of the1 #bic 8,right conduct01 #bcj ,rutherford1 ,sir ,e41 #ii1 #aja ,santayana1 ,mr41 #bcj ,schiller1 ,dr4 ,f4 ,c4 ,s41 #gi ,schrdinger1 #ih1 #aje1 #bgh1 #bic1 #bid ,self-observation1 #abf1 #afa ff4 basis of ,descartes's system1 #afb ff4 ,dr4 ,watson's views1 #afg ff4 gives knowledge not part of physics1 #age ,semon1 #di1 #ahj ,sensation1 difference between images and1 #agi acoleuthic1 #aig as opposed to perception1 #bjd ,sensitivity1 #ei f41 #hh1 #abc1 #agg ,sentences1 #ea1 #ed1 #ge1 #bee1 #bfd ,sequence1 laws of1 #aaf ,shakespeare1 #aib ,sheffer1 ,dr4 ,h4 ,m41 #bhb1 #bib ,sight1 compared with touch1 #aef f4 ,size1 sense of1 #aec ,socrates1 #bbf 8,solipsism01 #bia ,sommerfeld1 #ajc ,space1 one persistent1 abolished in relativity theory1 #ajh physical and perceptual1 #acg ff41 #bda f41 #bid ,space-time1 in theory of relativity1 #ajh ff4 structure of1 #ade point-instant in1 #bgh 8,specious present01 #aie1 #aig ,spinoza1 #bch1 #bea ,stars and ,atoms 7,eddington71 #bgi 8,statement01 definition of a1 #bfj ,subjectivity1 #abi1 #acc1 #ace1 #aed f4 ,substance1 #e1 #bdb ff41 #bic ,syllogism1 the1 #hj ,syntax1 influence of1 on philosophy1 #bdc connection between laws of physics and laws of1 #bfc ,talking without thinking1 #aij ,tendency1 quantitative laws of1 #add ,testimony1 #aa f41 #agj ,the ,analysis of ,matter 7,bertrand ,russell71 #bgh ,the ,meaning of ,meaning 7,ogden and ,richards71 #eb ,the ,mind and ,its ,place in ,nature 7,dr4 ,broad71 #gf1 #ahh1 #bhb ,thorndike's 8provisional laws01 #ca ff4 ,thought1 #afc ff41 #agd1 #bdj1 #bfc ,time1 not cosmic1 #ajh ff41 #aeh ,touch1 compared with sight1 #aef ,treatise on ,probability 7,keynes71 #bfi ff4 ,truth1 #id1 #bfa f4 ,truth and ,falsehood1 causes of mystery about1 #bed two questions in1 #bed ff4 meaning of a sentence examined1 #bee f4 grounds on which statements are regarded as true or false1 #beg ultimate test of falsehood1 #beh 8belief01 #beh ff4 problems of1 #bei ff4 ,universals1 #ec1 #bjc ,universe1 the1 philosophy concerned with1 #bcf man's relation to1 #bih ff4 8,unlearned ,equipment01 #bb ,utilitarian philosophy1 #bbi f4 ,vitalists1 #be ,volition1 #fa ,watson1 ,dr4 ,j4 ,b41 #aj1 #ba1 #bb1 #ca1 #cc1 #ce1 #cf1 #cg1 #gj ff41 #abf ff41 #afb1 #afg ff41 #agg1 #ahh1 #bai1 #bbc1 #bei ,waves in empty space1 #ajg f4 ,whitehead1 ,dr41 #aei 8,will01 #bbc f4 ,willing1 as mental occurrence1 #bjb ,winds of ,doctrine 7,santayana71 #bcj ,wish-fulfilment and dread-fulfilment1 #aid ,wittgenstein1 #bfd ,words1 purpose of1 #aa f4 as physical occurrences1 #dd ff4 spoken and written1 #df f4 how acquired by infants1 #dh ff4 meaning of1 #eb1 #bef relations of1 #ef in an ideal logical language1 #bef f4 ,world1 the physical1 nature of our knowledge of1 #aea ff4 a four-dimensional continuum of events1 #bic our knowledge of1 purely abstract1 #bie ,,the ,,end ,illustration ,,norton ,,books ,paul ,bekker ,,the ,,story ,,of ,,music #c4ej ,everett ,dean ,martin ,,psychology #c4jj ,,the ,,meaning ,,of ,a ,,liberal ,,education #c4jj ,daniel ,gregory ,mason ,,artistic ,,ideals #b4ej ,h4 ,a4 ,overstreet ,,influencing ,,human ,,behavior #c4jj ,a ,,book ,,about ,,ourselves #c4jj ,bertrand ,russell ,,philosophy #c4jj ,thomas ,e4 ,tallmadge ,,the ,,story ,,of ,,architecture ,,in ,,america #c4ej ,john ,b4 ,watson ,,behaviorism #c4jj ,,the ,,new ,,science ,,series ,,edited ,,by ,c4 ,k4 ,,ogden ,c4 ,judson ,herrick ,,fatalism ,,or ,,freedom #a4jj ,i4 ,a4 ,richards ,,science ,,and ,,poetry #a4jj ,vilhjalmur ,stefansson ,,the ,,standardization ,,of ,,error #a4jj ,announcements of other volumes in this series1 and a complete catalogue of ,norton ,books sent on request ,w ,w ,,norton ,,company1 ,,inc4 #gj ,fifth ,avenue ,new ,york ,transcriber's ,notes ,hyphenation1 and spelling were made consistent when a predominant preference was found in the original book2 otherwise they were not changed4 ,original text mostly placed commas and periods after closing quotation marks1 but occasionally placed them before closing quotation marks4 ,this inconsistency has not been changed here4 ,simple typographical errors were corrected2 unbalanced quotation marks were remedied when the change was obvious1 and otherwise left unbalanced4 ,footnotes have been sequentially renumbered and placed just below the paragraphs that reference them4 ,the index was not checked for proper alphabetization or correct page references4 ,page #hf3 ,the variables in the equation were printed in italics4 ,to improve readability1 the underscore characters used elsewhere to indicate italics have been omitted in this case4 ,page #bjg3 8this is a causal word0 originally was printed as 8this a a causal word02 changed here by ,transcriber4