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Descartes' argument for doubt in the First Meditation


To: James V.
From: Geoffrey Klempner
Subject: Descartes' argument for doubt in the First Meditation
Date: 3rd October 2008

Dear James,

Thank you for your email of 25 September, with your Introduction to Philosophy Introduction to Philosophy essay in response to the question, 'By what means does Descartes attempt to show that there is reason to doubt everything one believes?'

I enjoyed reading this essay. You have not only shown that you grasp the logical structure of Descartes' arguments in the First Meditation, but you also succeed in conveying a real sense of their urgency. Hard bitten examiners tend to ignore 'good writing' as such in philosophy. It is the arguments that matter. I agree with this to a large extent, but still something extra is conveyed by the way one puts across an argument apart from the bare logical structure.

Your use of 'she' as the default third person pronoun is quite rare amongst my students, although almost universal amongst philosophy lecturers these days.

The question does not invite you directly to criticize Descartes' argument, but obviously there is room to question the logic of the case he is putting forward, in order to arrive at the best interpretation, on the basis of the 'principle of charity' (an interpretation which makes a philosopher's argument look stronger rather than weaker is more likely to be correct).

In what follows, I will offer suggestions where you might have said more, or where questions arise which it would be useful to think about.

Descartes responds to the worry about false perceptual judgments by saying that it is indeed via our senses that we are able to correct incorrect judgements arrived at through sense perception. How, then, does the point about the possibility of false perceptual judgement advance his case? You say, 'So we are faced with the greater question, that, if our senses lie to us sometimes how can we trust them at all?'

Consider what one would say about a person who lies to you. 'I'm never going to believe anything you say, ever again.' Grown ups don't do this. We are prepared to forgive a lie and will trust someone who offers a sincere apology. But anyone can tell a lie. So why doesn't it follow, that 'if people sometimes lie to us how can we trust them at all?' Yet we do. You might reply that, whereas we totally rely on our senses for our empirical knowledge, knowledge by testimony is not the source of all our knowledge because we can investigate things directly for ourselves. Even so, it does seem a bit abrupt to conclude that we should mistrust our senses just because they sometimes deceive us.

An alternative reading would be that this first step is simply intended to convey the principle that it can seem to me, on the basis of sense perception, that P when in fact it is not the case that P. This is not yet sufficient grounds for doubt or scepticism. However, it is that principle which Descartes later relies on when he launches his dreaming and evil demon arguments. You can't logically deduce how things are in reality merely from how things seem. Inductive reasoning is involved. And that gives the sceptic all the room they need to launch their case.

I liked the fact that you focused on the question which Descartes dismisses fairly abruptly, concerning whether he might be insane. As you point out, one of the main symptoms of schizophrenia is visual and auditory illusions. The film 'A Beautiful Mind' (2001) based on the true story of mathematician John Forbes Nash conveys a vivid sense of a man battling with persistent illusions. The problem is that the conflict with reality does not stop there. A person who suffers from paranoia draws the 'wrong' conclusions from the evidence, creating a distorted reality which seems immune from empirical refutation, whether illusions are present or not. But if this is Descartes' worry, then his enterprise is scuppered before it can even start. If you can't trust the processes of your own reasoning, then there is no point attempting to go further. Harry Frankfurt, in his book 'Dreamers, Demons and Madmen' explores these issues.

One step that you appear to have overlooked is where Descartes considers that he is here 'by accident' rather than as a result of being created by God. What he says about this is very interesting: in that case there would be all the more reason for scepticism. If we just happened to be here, why should our knowledge be reliable? One answer would be that we have evolved to be creatures who rely on what they can discover about the world around them, so to this extent there is at least an empirical explanation of why there can be such a thing as 'knowledge'. In the absence of such an explanation, however, the atheist in Descartes' time was in a bit of a fix. That is because the possibility of knowledge implies a teleological dimension. Our cognitive apparatus has a purpose, and we need some explanation of how it comes about that it is sufficiently 'well designed' to fulfil that purpose.

I like the fact that you clearly distinguish the 'now dreaming' and the 'always dreaming' arguments. There is a point to be made here about the Matrix hypothesis. In the Matrix, there is such a thing as space. The dreamers are in pods which are located somewhere in the bowels of the earth. Whereas, on the evil demon hypothesis, 'space' is merely a concept which describes the experiences fed directly to us by the evil demon. In Berkeley's philosophy of idealism (or 'immaterialism'), this 'evil demon' is none other than God himself. From the point of view of idealism, there is nothing God can do to bring about the existence of 'matter' or 'space' in the Cartesian sense, no coherent concept which these words signify.

All the best,