The Incorrigibility of the Cogito

Mind Association

The Incorrigibility of the CogitoAuthor(s): Jonathan HarrisonSource: Mind, New Series, Vol. 93, No. 371 (Jul., 1984), pp. 321-335Published by: Oxford University Press on behalf of the Mind AssociationStable URL: http://www.jstor.org/stable/2254413 .

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Mind (I984) Vol. XCIII, 321-335

The Incorrigibility of the Cogito

JONATHAN HARRISON

There is a kind of sceptic who thinks that there is absolutely no proposition whatsoever that anybody knows. Such a sceptic is very likely to think that it is always possible that our cognitive capacities should lead us astray. Afortiori, he must hold (if he is logical) that it is always logically possible that our cognitive capacities should lead us astray. And it may be that this sceptic thinks it is because it is always logically possible for our cognitive capacities to lead us astray that there is absolutely no proposition that anyone knows. (It does not much matter for the purposes of the subsequent argument whether any sceptic actually has held the views I have just mentioned.)

I think some philosophers have supposed that Descartes has refuted the view of the sceptic that it is always logically possible for our cognitive capacities to lead us into error. If Descartes is right, there are at least three beliefs, and perhaps more, which are such that it is not even logically possible for our cognitive capacities to have led us astray when we arrive at them. If I believe (i) that I exist, or believe (ii) that I believe something, or believe (iii) that I am mentally modified in some way or other that is not specified, what I believe must be true. Bernard Williams, in his book: Descartes: The Project of Pure Enquiry, puts this by saying that there is a class of logically incorrigible propositions.

I think he, and I think Descartes also, thinks that it follows that there are some propositions which some people-i.e., anyone at all who believes these propositions, know to be true. However, I do not wish to get involved in questions about what either Descartes (or Williams) actually thought on these matters. What I wish to consider is whether there are any logically incorrigible propositions and whether it follows that, if there are, these propositions are known to be true by any person believing them.

I doubt whether the word 'incorrigible' is a good one. One speaks of people as being incorrigibly wicked but not, except jokingly, as being incorrigibly good. Analogously, though one can have opinions which are incorrigibly false, one cannot have opinions

321



322 JONATHAN HARRISON:

which, in any normal sense, are incorrigibly true. A true belief can be changed, but it cannot be corrected, because it is correct already. If, by saying that a belief was incorrigibly true, one meant that it was a true belief that the believer could not be made not to have (just as, if a man is incorrigibly wicked, he is both wicked, and cannot be made not to be) I suspect that there are no incorrigible beliefs. If there were, a person's belief that he existed (or that he ihought, or that he was mentally modified) would not be one of them. I knew a woman once who, during a breakdown, was convinced that she did not exist, and I was unable to persuade her that she was mistaken. The fact that someone believes what he does is always a contingent fact.

By 'incorrigible belief', however, Williams does not mean 'true belief which a person cannot be made not to have'. He means 'belief which is such that, if it is believed (which it does not have to be) it must be true'. More accurately, though the point is sometimes lost sight of, it is a belief which, if some specially privileged person has it, then his belief must be true. My belief that I exist or that I believe or that I am mentally modified may be incorrigible, but Smith's belief that I exist, or believe something, or am mentally modified is not incorrigible. Hence 'incorrigible', like 'non-inferential', is a relative term. A belief is not incorrigible, full stop. It is incorrigible when held by Jones, but not incorrigible when held by Smith (just as it may be inferred by Jones, but not inferred by Smith).

It seems to me obvious, pace the sceptic, that some people's beliefs are incorrigible in the sense that, if they have them, their cognitive capacities are such that it is impossible (in some way or other) that they should be mistaken. My belief that my name is Harrison is of this kind. It is such that, if I have it, and my cognitive capacities are such as they in fact are, and applied in the situation in which they are in fact applied, it must, in some sense or other of 'must', be true. I must be right on this matter. I suspect that I must be right in the way in which, if I have the capacities of a fairly competent golfer, and am faced with a one-inch putt, and have no motive to miss it, I must sink it. I (I should perhaps say that it does not seem to follow that whenever I believe some such thing as that my name is Harrison, I cannot be mistaken. All that is involved is that I should not be able to be mistaken on this particular occasion.)

It seems to me, however, that there is no more any logical

See my 'If I know I can't be wrong', in the Proceedings of the Aristotelian Society, 1978-9.



THE INCORRIGIBILITY OF THE COGITO 323

impossibility in my cognitive capacities leading me to believe that my name is Harrison although it is not, than there is any logical impossibility in my golfing capacities allowing me not to sink the putt. Indeed, my own preliminary intuition on this matter is that it is always logically possible for my cognitive capacities to lead me astray. So far as my cognitive capacities go, it is always logically possible that what I believe should be false, and that what is true should not be believed.

It has seemed to many, however, that if there are some incorrigible beliefs in the sense defined, then I must be wrong in thinking that my believing something can never provide a logical guarantee for what is believed being true. And it does look as if there are some incorrigible beliefs, because it does look as if, if I believe that I exist, or that I believe, or that I am mentally modified, what I believe logically must be true.

Though it is true, however, that, if I think I exist, what I think must be true, it is not true in virtue or any epistemological principle to the effect that certain beliefs (for example, beliefs about my own existence, or to the effect that I believe, or am mentally modified) are guaranteed simply in virtue of the infallibility of certain of man's capacities. What it is true in virtue of is two principles, neither of which has anything to do with the reliability of my intellect. The first of these two principles is to the effect that, if anything is modified in any way, say by possessing an attribute or standing in a relation to something, it must exist. The other is to the effect that the proposition that someone believes p, together with p, implies that what he believes is true. The first of these two principles seems to me to be incontrovertible. The second could be disputed by anyone who thinks such things as that that Smith believes there will be a sea battle tomorrow and there will be a sea battle tomorrow does not entail that what Smith believes is true; but since the proposition that I exist is not about the future, his doubts may in this context be ignored.

It is in virtue of the first principle that, if someone believes he exists, he must exist. It is in virtue of the second that, if he exists, his belief that he exists must be true. The two together, in virtue of the transitivity of implication, imply that if he believes that he exists, what he believes must be true. Neither of these principles has anything to do with his reliability, logical (if such a thing as logical reliability is possible) or otherwise.




Though it is certainly true that, if I think I exist, I must exist, this true statement contains a suggestio falsi, to the effect that there is something especially privileged about the belief that I exist in that it, unlike other beliefs, carries with it the implication that I must exist. This point can be clarified by using italics. If I say that, if I believe that I exist, I must exist, then this suggests that-if I believe something else, say that there are nine planets, I do not have to exist. This, of course, is not true. Whatever I believe, I must exist in order to believe it. The content or subject matter of belief has nothing whatsoever to do with it. But the content must have something to do with my alleged infallibility if this is to show anything at all about what I do or do not know.

Of course, if I say that, if I believe that I exist, what I believe must be true (here emphasising the word 'true'); any suggestion that this is not true of other beliefs is not a false suggestion. What is suggested is not true of other beliefs, or only one or two of them at most. But there is, nevertheless, something false suggested by the statement that, if I believe I exist, I must exist. This is because it is implied that there is a difference in this respect between it and, say, the belief that there are nine planets. It is suggested that though, if I believe that there are nine planets, I can be mistaken, if I believe that I exist, I cannot be mistaken. It is further suggested that I can be mistaken in the first place, though not in the second, because though I am not one hundred per cent reliable on the question of the number of planets, I am one hundred per cent reliable on the question of my own existence. There is, however, no difference between the two in one respect; if I believe that I exist, and do exist (as I must, if I believe that I exist) what I believe must be true, and if I believe that there are nine planets, and there are nine planets, what I believe must be true. And neither the passage from my believing that there are nine planets (when there are), nor the passage from my believing that I exist (when I do), to my beliefs' being true, has anything to do with my being especially reliable on such matters, or especially immune from error.

In other words, there is no direct route from believing that one exists to this belief's being true via some epistemological considerations about the infallibility of certain of my cognitive capacities in some circumstances. There is in fact a two step inference, by means of the two principles I have mentioned, which takes you to exactly the same conclusion that you would get to if there were a one step inference of this kind. There is no logical principle to the effect that




one can pass directly from a belief to its truth. It is a peculiar kind of coincidence, if you can call something which is a matter of logical necessity a coincidence, that in this particular case what one believes must be true. Perhaps, though that one has the belief implies that it is true, it does not relevantly imply that it is true. I do not wish to say-although I have been tempted to-that implication is not a transitive relatibn, and that (i) if I believe I exist, I must exist, and (ii) if I exist, my belief that I exist must be true, does not imply (iii) that, if I believe that I exist, my belief that I exist must be true. What I am maintaining is that, even though p v q and q v r does imply p v r, p v r may have misleading suggestions which p D q and q v r do not have. For example, if it is true that, if I want to rob a bank, I will shoot a policeman, and that if my brain is in a certain degenerate condition I will want to rob a bank, it follows, by the transitivity of implication, that if my brain is in degenerate condition, I will shoot a policeman. But the statement that, if my brain is in a degenerate condition I will shoot a policeman, suggests, though it does not logically imply, that my wanting to rob a bank has nothing to do with my shooting a policeman and that I will shoot him whether I want to or not. Similarly, that if I believe that I exist what I believe must be true, suggests, though it does not imply, that there is a direct passage in this case from belief to truth, perhaps in virtue of a special cognitive capacity possessed by the believer which makes him infallible on such matters. There is no such suggestion in the two propositions, from which this proposition follows, (i) that if he believes he exists, he must exist, and (2) if he believes he exists, and does, what he believes must be true.

So much for the reasons for thinking that my belief that I exist is not a belief which guarantees its own truth. There are also reasons for thinking that my belief that that I think does not guarantee its own truth. The word 'think' can be understood in two relevant ways. (There are some irrelevant ways in which it can also be understood, for example, to mean 'rationate' or 'deliberate'; but there is no case for saying that, if I think I rationate or deliberate, what I think must be true.) First, 'think' may be taken to mean (and actually often does mean) 'believe'. Secondly it was taken by Descartes to mean (although it does not mean) 'be mentally modified' (perhaps by believing, but also, perhaps, by doubting, wondering, fearing, and so on).

If 'think' is taken to mean, firstly, 'believe', then it is possible to




argue that, if I believe that I believe something, I cannot be mistaken, for to believe one believes something is to believe something. If 'think' is taken to mean, secondly, 'be mentally modified', this gives rise to the argument that, if I think I am mentally modified, I must be mentally modified, for to think that one is mentally modified is one way of being mentally mnodified.

I do not wish to dispute fot one moment that, if one believes one believes such-and-such, one believes something, or that, if one believes one is mentally modified in such-and-such a way, one is mentally modified in some way. More than this, however, is necessary to show that either of these two beliefs are incorrigible in the sense that, if they are believed, they must be true. It is also necessary that one must believe something, or be mentally modified, in such a way that one's belief or mental modification is the very same belief or mental modification that one believes one has. Let us suppose that (believing myself to be a modest man) I believe that I believe that I am no better than my neighbour. In this case, though I have a belief about a belief, there is no reason why this belief about a belief should not be false. The belief I have-my belief that I believe that I am no better than my neighbour-is not such as to make itself true, for what I believe is not that I have this belief, but that I have the belief that I am no better than my neighbour. Hence there is no reason why I should not believe falsely that I believe I am no better than my neighbour.

In fact, whenever I believe that I believe some specified thing, for example, that I believe that I am no better than my neighbour, my belief must always be of an order one higher up than the belief it is about, and so it is impossible for the two beliefs to be the same. Such beliefs, therefore, cannot possibly be incorrigible. (Nor can they be, as it is sometimes said they are, self-verifying.)

Perhaps, however, it is possible that when I believe that I believe something that is not specified, what I believe must be true. For example, if I believe that I believe at least one thing, when I do not say what that one thing is, then, perhaps, what I believe must be true, for believing that one believes at least one thing is believing at least one thing.

It would be an unfortunate consequence of the view, that such unspecified beliefs are self-verifying, that there are certain beliefs which other people can truly have about me, but which I cannot




truly have about myself; if I do have them about myself, they must be false. There would be no difficulty in someone else believing truly that I have no beliefs whatsoever. But, if my belief, that I believe something, is self-verifying (and so incorrigible), I could not believe truly that I had no beliefs whatsoever, because my believing this would itself be a belief. Supposing I did have no beliefs whatsoever, this is a fact about myself which I could never come to know (if knowing implies believing) though other people could discover this about me. As soon as I came to believe it, I would have come to have a belief, and this would make it false.

Another consequence of the view that the belief that I have at least one belief is self-verifying and so cannot be false is that there are some propositions that can be 'entertained' (or considered), and can be true when entertained, but become false as soon as they are believed. Furthermore, if one were (inconsistently, if beliefs are self- verifying, but there is nothing impossible about being inconsistent) to believe that all one's beliefs were false, this belief would, if true and about itself, entail that it itself was false; if it was false, this would entail that it was true.

To digress just a little, there are also some beliefs which, though not directly about themselves, are so indirectly. If Paddy believes that everything the Pope believes is true, and the Pope believes that everything Paddy believes is false, then one of Paddy's beliefs, together with a matter of fact about the Pope which Paddy may or may not believe, entails that this belief itself is false. (The Pope's belief is also indirectly about itself, but in this case no paradox arises.) It may be that, to use a possibly misleading analogy, though a (straight) pointer cannot point directly to itself, it can point indirectly to itself by pointing to a pointer which is pointing to it.

These unfortunate consequences (other than those about the indirectly self-verifying beliefs mentioned in the preceding para- graph) of this view would not arise if a belief could not be directly about itself; but then there would be no case for saying that the belief that I believe something is incorrigible. It certainly seems, however, that some propositions may be about themselves. The law of the excluded middle seems to apply to the law of the excluded middle, and it looks as if the proposition, that every proposition implies itself, implies itself. Perhaps the proposition that there are some propositions that are neither true nor false is, or permits itself to be, neither true nor false. And paradoxes do not always arise when a proposition is taken to apply to itself.




However, in the permissible cases above, a generalisation is made about a class of propositions, which can be identified by means of a description that this generalisation itself fits. You can identify a proposition without identifying the proposition you are asserting. Hence in these cases, perhaps, a proposition can be about itself. When the proposition I am believing is a proposition about all beliefs, perhaps it can be about itself, for one does not have to identify this belief (the belief about all beliefs) in order to understand what a belief is. Hence, retrospectively, one may realise that one's former belief (which one may still have), about all beliefs, applies to itself, even if one cannot identify, or even think of, this belief at the moment one has it. And some propositions about beliefs in the sense of acts of believing, as opposed to believed propositions, do seem to apply to themselves. The belief that all beliefs can vary in intensity, for example, can vary in intensity.

The belief that I have at least one belief, though not a generalisation about beliefs, is still about a class of beliefs-the 'class' of my beliefs-to the effect that it has an instance-which class can be identified without identifying the belief that I have at least one belief. So perhaps it can be about itself. And if it can be about itself, then it must be self-verifying and so incorrigible.

One cannot, however, adduce as a reason, for thinking that my belief that I have at least one belief is true, that I believe I have at least one belief. The belief that would 'self-verify' it, so to speak, cannot be produced by the believer as a reason for believing it. For, in order to do this, the believer must not only have a belief about the class of his beliefs in general (to which he may subsequently discover that his belief that he believes at least one thing belongs); he must have a belief which is quite explicitly about itself, as my belief that I believe that the earth isflat is explicitly about my belief that the earth is flat. This, however, is impossible. The attempt to say what one is believing in this case leads to an infinite regress. For spelt out in full, what I believe is that I believe at least one thing, viz., that I believe at least one thing. . . . (Compare this with 'I believe at least one thing, viz., that the earth is flat'.) Since the 'that clause' 'that I believe at least one thing' still does not tell you what it is that you believe, it needs further specification by another similar 'that-clause', which gives you 'I believe at least one thing, viz., that I believe at least one thing, viz., that I believe at least one thing.. ..' But however long you continue this process, you get left with a 'that clause' which still does not specify what it is that you believe.




Furthermore, if A says to B, 'I believe at least one thing', B can properly reply 'Oh yes. What?' A cannot informatively answer 'That I believe at least one thing', because B can still say 'What?' with just as much reason as he had before. It follows from this that my belief can be specified by someone else, but not by me. (There is no reason, however, why I should not believe that I believed (in the past tense) only one thing-which at most only contextually implies that I do so no longer-but in this case I do not specify the belief I have now, but a similar belief I had, perhaps only a short while ago. And in any case, the belief that I believed at least one thing must still, when spelt out fully, be the belief that I believed at least one thing other than this belief (the belief that I believed at least one thing), for example, that the earth is flat.)

If a man believes that he believes that the earth is flat, it is possible for him to believe that this is the only thing he believes. (If his belief that it is the only thing he believes-i.e. the only instance of the class of his beliefs-can be about itself, it follows, inconveniently, that this belief must be false, for, if he has it, he must then believe two things, that he believes that the earth is flat, and that he believes that this is his only belief. It further follows that if his beliefs could be about themselves, and he did believe he had two beliefs, viz., that he believed that the earth was flat and that this is his only belief, he would then have three beliefs.) But if he believes at least one thing, it is not possible for him to believe that this is the only thing he believes. If it is true, there must be some belief other than his belief that he believes only one thing, i.e. that one belief which he truly believes he has. (It is possible for someone else to believe, about him, that that he believes only one thing is the only thing he believes, from which it would follow that, if this other person's belief is true, his belief must be false.) He cannot believe that his belief that he believes at least one thing is the only belief he has, because in that case he would have to specify what this only belief was, and this we have seen he cannot do. (It does not follow that he cannot believe that he has one and only one belief, when he does not specify what this one and only one belief is.)

That it is impossible to believe that one's belief that one believes only one thing is both true and one's only belief is made more obvious when one considers analogous utterances, utterances which one might make when one is doing things other than express one's beliefs in words. One's promise to keep a promise cannot be one's only promise; there must be some other promise which this promise




commits him to keeping. The expression 'I promise to keep this

promise' where the words 'this promise' refer to the promise to keep

this promise, is quite illegitimate. No-one, using such words with

this reference, can succeed in making a promise. It would be equally

illegitimate to say 'I command you to obey this command', when

'this command' refers to the command to obey this command. Nor

can one assert that this assertion is true, expect that this expectation

will be fulfilled, intend that this intention be carried out, wish that

this wish be granted, or hope that this hope is realised. (For the same

reason, one cannot believe that this belief is held.) And, just as there

cannot be self-verifying beliefs, so there cannot be self-obeying commands (e.g., the command to oneself to issue this command),

self-verifying assertions (e.g., the assertion that one is asserting this

assertion), self-keeping promises, self granting wishes, or self-

fulfilling hopes. From all this it follows that, even if one could have a belief which

is about itself, one could not have a belief which is explicitly about

itself. From this it further follows that, even if the belief that one

believes only one thing is self-verifying, it cannot be known to be

true by the believer. He cannot know it to be true unless he can have

conclusive reason for thinking it to be true, and he cannot have

conclusive reason for thinking it to be true unless he can believe,

and so be able to know the truth of, the proposition from- which it

follows, and the proposition from which it follows is a proposition

which he cannot even formulate. To try to do so is like trying to

catch one's thumb with one's thumb. It may be relevant to remark that there may be two criteria for

deciding what it is that one believes. One appeals to the intentions of

the believer; the other to the conventional rules governing the

meaning of the words in the sentence which express the belief in

question. Given the conventional rules for the use of the expression

'belief', one's belief that one believes only one thing is a belief, and is

about itself. But if what one is asserting depends upon one's

intentions, the belief that one believes at least one thing cannot be

about itself, for it is impossible for the intentions involved in a belief

to refer to themselves. (This would tend to support the old-

fashioned view that no act of introspection can be directed upon

itself.) If one believes the proposition expressed by the sentence

'The man in the blue suit is a detective', and the person one intends

to refer to is a woman, then one is, if one's beliefs are determined by

one's intentions, referring to this person; if what one believes is



THE INCORRIGIBILITY OF THE COGITO 33I

determined by the conventional meaning attached to the words which express one's belief, then one is not referring to anyone.

If what I believe (or assert) is determined by the conventional meanings of the words in which I express my belief (or assertion), then, if I believe that the candidate with ten coins in his pocket (i.e., Smith) will get the job, and Jones has ten coins in his pocket, and gets the job, than what I believe (or have asserted) is true. But if it is determined by my intentions, then what I believe is false. For in that case what I believe is not that the man with ten coins in his pocket, whoever he may be, will get the job, but that the man with ten coins in his pocket (i.e. Smith) will get the job, and this is not true. Similarly, if I believe that I believe at least one thing, i.e., that the earth is flat, and I do not believe that the earth is flat, but do believe that it is round, then, if what I believe is determined by the conventional meanings of the words in the sentence which ex- presses my belief, what I believe is true, but if it is determined by my intentions, what I believe is false.

It follows from what I have been saying that one must draw a distinction between the belief a proposition that one asserts evinces, and the belief it is about (when it is about a belief at all). If I say that I believe that the earth is flat, then my belief that the earth is flat, which this proposition is about, is a different belief from the belief of which my asserting it is normally a manifestation, i.e., my belief that I believe that the earth is flat. If what I have been saying is true, it follows that the belief I assert I have and the belief I evince in making this assertion are necessarily different. There is further no reason why I should not say, at one time, that I had a belief at an earlier time which, at the earlier time, I can only evince. If I say at I 2

o'clock that I believe I have only one belief, my belief that I believe I have only one belief can at that time only be evinced. But, at I 2.0 I I can say that at I 2.00 I believed that I believed I had only one belief, for my saying this will not evince the belief that I believed that that I had only one belief, but the belief that I believed that I believed that I had only one belief.

Let us turn to the second interpretation of the statement that, if I think I think, what I think must be true. According to this second interpretation it means that if I believe I am mentally modified, I must be mentally modified (because believing is one way of being mentally modified), and so what I believe must be true.

Again, the conclusion does not necessarily follow if it is specified




in what way I believe I am mentally modified. I may, for example, think that I am mentally modified by doubting, in which case, though it does follow that I am mentally modified, it is not by doubting, but by believing. It is only if I believe that I am mentally modified by believing that my belief has any chance of being incorrigible. And then, if it is specified what the object of my belief is, it is, as we have seen, impossible for the belief I have and the belief I believe I have to be identical. It is only if this is not specified that my belief that I am mentally modified-by believing something or other-could possibly be incorrigible. And we have seen reason for doubting that, even in this case, what I believe can be incorrigible.

It must not be forgotten that the fact that, if I believe I am mentally modified in some way or other my belief must be true, provides no answer to scepticism, and has no tendency to show either that I know that I am mentally modified-because I am especially reliable on such matters-or how I know that I am.

That it does not show that I know that I am mentally modified can be further demonstrated by the following example. I might, after reading the first part of the Meditations (and not understanding all of it), come to think (mistakenly) that I had succeeded in doubting everything I formerly believed. If I had succeeded in doing this, of course, it would follow that I was mentally modified, since doubting is a kind of mental modification. Hence I might deduce, from the fact that I had (as I thought) succeeded in doubting everything, that I was mentally modified. If such beliefs can be about themselves, and are consequently incorrigible then this belief must be true. But even if it is a belief that must be true, this does not show that I know it to be true. Indeed, since I have inferred it from the false proposition that I have succeeded in bringing myself to doubt everything, I do not know it to be true. Hence, even though I do believe it, and my belief must be true, I have no good reason for believing it when I ought to have, and so cannot know it.

The same is also true of the first of the two arguments we have been considering, i.e., the one in which we took 'think' to mean 'believe'. Even conceding that the belief that I believe something or other can be about itself, and this belief is self-verifying and so incorrigible in consequence, it would not follow from the fact (if it is one), that if I believe that I believe something or other I must be right, that I know that I believe something or other. To return to my former example, I may believe that I believe something or other




because (believing myself to be a modest man) I believe that I believe that I am no better than my neighbour. That I should believe this, however, is a case of self-deception; I am in fact a conceited man, and do not believe I am no better than my neighbour. (Indeed, though I do not realise it, I believe I am better than my neighbour.) Since, again, I infer that I believe something or other from the false proposition that I believe I am no better than my neighbour, I have no reason whatsoever for believing that I believe something. Hence I do not know that I believe something.

Hence the fact, if it is one, that there are incorrigible beliefs which must be true does not provide any answer to scepticism by way of showing that there is at least one proposition that I must know. Still less would the fact, if it is a fact, that if I believe I believe something or believe that I am mentally modified, my belief must be true, show how I know that I believe something, or how I know I am mentally modified.

The same considerations also show that the fact that if I think I exist what I think must be true, does not show that I know that I exist. Let us suppose that the woman whom I mentioned earlier, who did not believe that she existed, went to a psychiatrist to be reassured on this important matter, and that, as a rather crude psychiatrist might do, he gave her the reassurance she needed. She would then have come to believe on this psychiatrist's testimony that she existed. He might, however, like many psychiatrists, have the reprehensible habit of reassuring his patients even when their fears were well gounded. In this case, he would not be a reliable authority, and her belief that she existed, accepted on his dubious word, would not amount to knowledge, in spite of its being the case that the very fact that she has it entails that it must be true.

Though, if I know something, what I know must be true

(D (Akp v p)) in the sense that my knowing it entails that it is true, and though, if I know something, my belief that it is true cannot be false (Akp vD D(Abp v p)) it would be a mistake to suppose that, whenever I believe something that cannot be false, this belief must amount to knowledge (D(Abp D p) v Akp or Abp iIp v Akp).

It is a mistake to supp6se that a small boy's belief that.Pythagoras' Theorem is true must amount to knowledge because this theorem cannot be false. Though Pythagoras' Theorem is necessarily true, its truth is not necessitated by the small boy's belief, and it is the




latter that would have to obtain, not the former, for this child's belief to be knowledge.2 (This, incidentally, is one of a number of examples which show that an impossibility of p's being true and q false is quite different from an entailment of q by p.)

To suppose that, if I believe that I exist, that I think, or that I am mentally modified, then my belief must be true, entails that I know that I exist, that I think, or that I am mentally modified would in one way be like supposing that if what someone believes cannot be false (because it is necessarily true), it follows that he knows that it is true. Though whenever someone knows something, it is impossible for him to be mistaken, it does not follow that, whenever it is impossible for him to be mistaken he knows that which it is impossible for him to be mistaken about.

In another way, however, the two cases are quite different. There is no impossibility of my not existing, or not thinking or not being mentally modified, as there is of Pythagoras' Theorem's not being true. It is impossible for these three propositions to be false only if they are believed by me. In the case of believing Pythagoras' Theorem, the mistake of supposing that I must know it, if I believe it, is the mistake of confusing the proposition that my belief that it is true cannot be false (because that proposition which is the object of my belief cannot be false) with the proposition that that my belief that it is true guarantees that it is true cannot be false. Only the latter entails that I know that Pythagoras's Theorem is true.

In the case of my inability to be mistaken when I believe that I exist, think or am mentally modified, the mistake of confusing these inabilities with that inability to be mistaken which is necessary for knowledge is that of supposing that because, in both cases, the hypothetical proposition that if I believe p then p is necessarily true, I must know its antecedent. The mistake involved in that of supposing that I must know these propositions if, if I believe them they must be true, is the mistake of confusing two different kinds of necessity. The necessity that obtains in the case of these three is logical necessity. The necessity which must obtain, if I am to know them, would be that kind of necessity which is the opposite of the possibility of my cognitive capacities leading me into error on matters such as this. This necessity cannot be logical for, of course, I may know many things; such as that my name is Harrison, where my belief that they are true does not logically guarantee its own

2 See my 'If I know I can't be wrong', P.A.S., 1978-9.




truth. Indeed, the arguments that, if I believe that I exist, think or am mentally modified, what I believe must be true, has nothing whatsoever to do with the reliability of the cognitive capacities of the person who believes these propositions. The arguments about existence rest on the twin principles (i) that whatever is modified in a certain way must exist, and (2) that if I believe so-and-so, and so- and-so, then my belief that so-and-so is true. The arguments about believing that I believe something and believing that I am mentally modified rested on the (questionable) assumption that some beliefs are self-verifying. Neither argument had anything to do with the cognitive capacities of the believer making it impossible for him to be mistaken on the subject in question; all they did, as we have seen, is to lead to the same conclusion that an argument resting on such a principle would have led to. Hence they do nothing whatsoever to show that I know that I exist, that I think, or that I am mentally modified. Still less do they have the slightest tendency to answer the important epistemological question about how I know these three things.

My argument to this conclusion is re-inforced by the fact that the truth of the three propositions, that if I think I exist, that I think, or am mentally modified, what I think must be true, does not even enable one to put the belief that I exist, think or am mentally modified into one or other of two major categories in the theory of knowledge, the category of beliefs that are inferred and that of beliefs that are not. (I shall assume, for the sake of argument, that there are some beliefs that are not inferred, though it is common these days to deny it.) Whether I infer that I exist, that I think, or am mentally modified, or know these things without inference, it is still true that, if I think that I- exist, think or am mentally modified, what I think must be true. Hence that these propositions are so would neither show that I know these things, nor how I know them-though that I do know them in fact it would be folly to dispute.

DEPARTMENT OF PHILOSOPHY,

UNIVERSITY OF NOTTINGHAM,

NOTTINGHAM NG7 2RD.



The Incorrigibility of the Cogito

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