Chapter XI. On Intuitive Knowledge

by Bertrand Russell

　　There is a common impression that everything that we believe ought to becapable of proof, or at least of being shown to be highly probable. It isfelt by many that a belief for which no reason can be given is anunreasonable belief. In the main, this view is just. Almost all our commonbeliefs are either inferred, or capable of being inferred, from otherbeliefs which may be regarded as giving the reason for them. As a rule,the reason has been forgotten, or has even never been consciously presentto our minds. Few of us ever ask ourselves, for example, what reason thereis to suppose the food we are just going to eat will not turn out to bepoison. Yet we feel, when challenged, that a perfectly good reason couldbe found, even if we are not ready with it at the moment. And in thisbelief we are usually justified.

　　But let us imagine some insistent Socrates, who, whatever reason we givehim, continues to demand a reason for the reason. We must sooner or later,and probably before very long, be driven to a point where we cannot findany further reason, and where it becomes almost certain that no furtherreason is even theoretically discoverable. Starting with the commonbeliefs of daily life, we can be driven back from point to point, until wecome to some general principle, or some instance of a general principle,which seems luminously evident, and is not itself capable of being deducedfrom anything more evident. In most questions of daily life, such aswhether our food is likely to be nourishing and not poisonous, we shall bedriven back to the inductive principle, which we discussed in Chapter VI.But beyond that, there seems to be no further regress. The principleitself is constantly used in our reasoning, sometimes consciously,sometimes unconsciously; but there is no reasoning which, starting fromsome simpler self-evident principle, leads us to the principle ofinduction as its conclusion. And the same holds for other logicalprinciples. Their truth is evident to us, and we employ them inconstructing demonstrations; but they themselves, or at least some ofthem, are incapable of demonstration.

　　Self-evidence, however, is not confined to those among general principleswhich are incapable of proof. When a certain number of logical principleshave been admitted, the rest can be deduced from them; but thepropositions deduced are often just as self-evident as those that wereassumed without proof. All arithmetic, moreover, can be deduced from thegeneral principles of logic, yet the simple propositions of arithmetic,such as 'two and two are four', are just as self-evident as the principlesof logic.

　　It would seem, also, though this is more disputable, that there are someself-evident ethical principles, such as 'we ought to pursue what isgood'.

　　It should be observed that, in all cases of general principles, particularinstances, dealing with familiar things, are more evident than the generalprinciple. For example, the law of contradiction states that nothing canboth have a certain property and not have it. This is evident as soon asit is understood, but it is not so evident as that a particular rose whichwe see cannot be both red and not red. (It is of course possible thatparts of the rose may be red and parts not red, or that the rose may be ofa shade of pink which we hardly know whether to call red or not; but inthe former case it is plain that the rose as a whole is not red, while inthe latter case the answer is theoretically definite as soon as we havedecided on a precise definition of 'red'.) It is usually throughparticular instances that we come to be able to see the general principle.Only those who are practised in dealing with abstractions can readilygrasp a general principle without the help of instances.

　　In addition to general principles, the other kind of self-evident truthsare those immediately derived from sensation. We will call such truths'truths of perception', and the judgements expressing them we will call'judgements of perception'. But here a certain amount of care is requiredin getting at the precise nature of the truths that are self-evident. Theactual sense-data are neither true nor false. A particular patch of colourwhich I see, for example, simply exists: it is not the sort of thing thatis true or false. It is true that there is such a patch, true that it hasa certain shape and degree of brightness, true that it is surrounded bycertain other colours. But the patch itself, like everything else in theworld of sense, is of a radically different kind from the things that aretrue or false, and therefore cannot properly be said to be true.Thus whatever self-evident truths may be obtained from our senses must bedifferent from the sense-data from which they are obtained.

　　It would seem that there are two kinds of self-evident truths ofperception, though perhaps in the last analysis the two kinds maycoalesce. First, there is the kind which simply asserts the existenceof the sense-datum, without in any way analysing it. We see a patch ofred, and we judge 'there is such-and-such a patch of red', or morestrictly 'there is that'; this is one kind of intuitive judgement ofperception. The other kind arises when the object of sense is complex, andwe subject it to some degree of analysis. If, for instance, we see a roundpatch of red, we may judge 'that patch of red is round'. This is again ajudgement of perception, but it differs from our previous kind. In ourpresent kind we have a single sense-datum which has both colour and shape:the colour is red and the shape is round. Our judgement analyses the datuminto colour and shape, and then recombines them by stating that the redcolour is round in shape. Another example of this kind of judgement is'this is to the right of that', where 'this' and 'that' are seensimultaneously. In this kind of judgement the sense-datum containsconstituents which have some relation to each other, and the judgementasserts that these constituents have this relation.

　　Another class of intuitive judgements, analogous to those of sense and yetquite distinct from them, are judgements of memory. There is somedanger of confusion as to the nature of memory, owing to the fact thatmemory of an object is apt to be accompanied by an image of the object,and yet the image cannot be what constitutes memory. This is easily seenby merely noticing that the image is in the present, whereas what isremembered is known to be in the past. Moreover, we are certainly able tosome extent to compare our image with the object remembered, so that weoften know, within somewhat wide limits, how far our image is accurate;but this would be impossible, unless the object, as opposed to the image,were in some way before the mind. Thus the essence of memory is notconstituted by the image, but by having immediately before the mind anobject which is recognized as past. But for the fact of memory in thissense, we should not know that there ever was a past at all, nor should webe able to understand the word 'past', any more than a man born blind canunderstand the word 'light'. Thus there must be intuitive judgements ofmemory, and it is upon them, ultimately, that all our knowledge of thepast depends.

　　The case of memory, however, raises a difficulty, for it is notoriouslyfallacious, and thus throws doubt on the trustworthiness of intuitivejudgements in general. This difficulty is no light one. But let us firstnarrow its scope as far as possible. Broadly speaking, memory istrustworthy in proportion to the vividness of the experience and to itsnearness in time. If the house next door was struck by lightning half aminute ago, my memory of what I saw and heard will be so reliable that itwould be preposterous to doubt whether there had been a flash at all. Andthe same applies to less vivid experiences, so long as they are recent. Iam absolutely certain that half a minute ago I was sitting in the samechair in which I am sitting now. Going backward over the day, I findthings of which I am quite certain, other things of which I am almostcertain, other things of which I can become certain by thought and bycalling up attendant circumstances, and some things of which I am by nomeans certain. I am quite certain that I ate my breakfast this morning,but if I were as indifferent to my breakfast as a philosopher should be, Ishould be doubtful. As to the conversation at breakfast, I can recall someof it easily, some with an effort, some only with a large element ofdoubt, and some not at all. Thus there is a continual gradation in thedegree of self-evidence of what I remember, and a corresponding gradationin the trustworthiness of my memory.

　　Thus the first answer to the difficulty of fallacious memory is to saythat memory has degrees of self-evidence, and that these correspond to thedegrees of its trustworthiness, reaching a limit of perfect self-evidenceand perfect trustworthiness in our memory of events which are recent andvivid.

　　It would seem, however, that there are cases of very firm belief in amemory which is wholly false. It is probable that, in these cases, what isreally remembered, in the sense of being immediately before the mind, issomething other than what is falsely believed in, though somethinggenerally associated with it. George IV is said to have at last believedthat he was at the battle of Waterloo, because he had so often said thathe was. In this case, what was immediately remembered was his repeatedassertion; the belief in what he was asserting (if it existed) would beproduced by association with the remembered assertion, and would thereforenot be a genuine case of memory. It would seem that cases of fallaciousmemory can probably all be dealt with in this way, i.e. they can be shownto be not cases of memory in the strict sense at all.

　　One important point about self-evidence is made clear by the case ofmemory, and that is, that self-evidence has degrees: it is not a qualitywhich is simply present or absent, but a quality which may be more or lesspresent, in gradations ranging from absolute certainty down to an almostimperceptible faintness. Truths of perception and some of the principlesof logic have the very highest degree of self-evidence; truths ofimmediate memory have an almost equally high degree. The inductiveprinciple has less self-evidence than some of the other principles oflogic, such as 'what follows from a true premiss must be true'. Memorieshave a diminishing self-evidence as they become remoter and fainter; thetruths of logic and mathematics have (broadly speaking) less self-evidenceas they become more complicated. Judgements of intrinsic ethical oraesthetic value are apt to have some self-evidence, but not much.

　　Degrees of self-evidence are important in the theory of knowledge, since,if propositions may (as seems likely) have some degree of self-evidencewithout being true, it will not be necessary to abandon all connexionbetween self-evidence and truth, but merely to say that, where there is aconflict, the more self-evident proposition is to be retained and the lessself-evident rejected.

　　It seems, however, highly probable that two different notions are combinedin 'self-evidence' as above explained; that one of them, which correspondsto the highest degree of self-evidence, is really an infallible guaranteeof truth, while the other, which corresponds to all the other degrees,does not give an infallible guarantee, but only a greater or lesspresumption. This, however, is only a suggestion, which we cannot as yetdevelop further. After we have dealt with the nature of truth, we shallreturn to the subject of self-evidence, in connexion with the distinctionbetween knowledge and error.