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Descartes on the incorrigibility of mental events


To: Tony L.
From: Geoffrey Klempner
Subject: Descartes on the incorrigibility of mental events
Date: 15 September 2006 10:22

Dear Tony,

Thank you for your email of 6 September, with your essay for the University of London Introduction to Philosophy program in response to the question, ''I am now seeing light, hearing a noise, feeling heat. But I am asleep so all this is false. Yet I certainly seem to see, hear, be warmed. This cannot be false' (Descartes). Discuss.'

This is a very thorough examination of the claim, or rather claims which Descartes makes in the above quote. As you observe, there are two main questions: one concerning the 'I' and the other concerning the occurrence of mental events. Let's look at each of these in turn.

As many critics of Descartes have argued, the use of 'I' in the statement, 'I certainly seem to see...' is questionable, insofar as it presupposes an entity with an identity over time. If Descartes is seriously in the business of doubting everything that can be doubted, then it should be perfectly conceivable that the evil demon created him five seconds ago, along with set of false memories concerning 'his' past experiences.

However, we have to distinguish this from the more radical, Humean criticism which rejects the idea that one needs an 'I' as a container or subject of experiences in addition to the experiences themselves. You raise the worry of how one can assign a given experience to one bundle or another. In fact, it seems that the Humean has ample resources to do this. Just define 'co-presence' as a symmetrical, reflexive and transitive relation which can hold between any two perceptions at a given time. It follows that experiences will be neatly partitioned into non-overlapping bundles. Experiences belong to the GK bundle (at a given time) so long as they are co-present with, say, 'this coffee taste' (as I take a sip). So, on this view, one does not need 'I' at all.

Of course, if you were then to ask WHY co-presence must be symmetrical, reflexive and transitive that is a question which Hume does not address - but Kant does (in his notion of the formal 'I think' which 'accompanies all perceptions').

You are not expected to be able to quote from Hume and Kant. However, Strawson in the other reading has something relevant to say. We have seen that it is possible to doubt one's identity over time. In, fact, as Strawson would argue, there is NO DIFFERENCE in the Cartesian picture between identity and non-identity. Imagine that 'I' die at every moment and am replaced by a duplicate 'I'. This is not intended as a sceptical claim, but rather as attacking the very idea of 'identity' as applied to the Cartesian 'I'. (The original source of this criticism is Kant's 'Paralogisms of Transcendental Psychology' from the Critique of Pure Reason'.)

Even worse, there is no coherent meaning, Strawson claims, in the idea that there is one 'I' enjoying these momentary perceptions rather than a thousand 'I's. Take away body, and you take away the only thing that is capable of conferring identity on a subject of experience, either at a time or over time.

What about the perceptions themselves?

As you argue, Descartes draws a contrast between thoughts that can be false, where there is a gap between seeming and reality, and thoughts that can't be false because there is no gap. The question is, Is that a way of being necessarily true?

You cast doubt on this claim, on the ground that even if the experience as such cannot be doubted, as soon as I try to express the experience in words there arises the possibility of making an error, using the wrong words.

However, this still seems to give the Cartesian a last-ditch position which rejects discursive knowledge - there are no indubitable thoughts I can express in words which capture the 'this' of my present experience - yet manages to hold onto the thing that matters most, the hard nugget of metaphysical fact that there is 'this, now'.

Your comment on this position is that it is too slender a foundation on which to build a system of knowledge. Whether that is the case or not, however, the question is whether Descartes is ultimately right, there is a 'something that cannot be doubted'. If there is, then it looks like mind-body dualism (which is advertised in the full title of the Meditations as Descartes' goal) must be true in some form. If there is a 'something' that can exist in the absence of matter, then materialism must be false.

You might like to think about ways of attacking this final defence position of Cartesian philosophy.

I have written something relevant to this. See my paper, 'Truth and subjective knowledge' at

All the best,