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Descartes' case for doubt in the First Meditation


To: Gurdeep K.
From: Geoffrey Klempner
Subject: Descartes' case for doubt in the First Meditation
Date: 10th March 2011 12:42

Dear Gurdeep,

Thank you for your email of 26 February with your essay for the University of London Diploma Introduction to Philosophy module, in response to the question, 'What reasons does Descartes give us for doubting all our beliefs? Are they good reasons?'

This essay is not too bad, although I think you lost the thread a bit towards the end when you consider the evil demon argument. But more of that in a minute.

Descartes sets out, as you observe, to cast doubts on all our beliefs in order to discover whether there are any beliefs that cannot be doubted. For the purpose of this essay, however, we don't need to consider his ulterior purpose of 'finding secure foundations for knowledge'. We are only concerned with the strength of the reasons which Descartes gives for 'doubting all our beliefs'.

Why does he give three arguments? Don't you think that's a good question to ask? Imagine an evil demon who is all powerful, who has deliberately set out to create experiences in your mind which do not correspond with reality. If the scenario of an evil demon which I have just described is logically possible, and there is no way to defeat that hypothesis on the basis of sense experience, then surely in a single blow Descartes has cast doubts on all our beliefs based on experience! That's all he needs to do.

Imagine that you are considering buying a new computer. The model you are looking at is the only model that enables you to do all the work you want to do. That is a clinching argument, there's nothing more to say. Now imagine someone challenged your decision. The first thing you say is, 'I like the curvy lines and the colour scheme.' 'Maybe you do,' your friend replies, 'but that's not a good enough reason.' 'OK, then, well I've always wanted an Apple computer.' 'But that's not a good enough reason, if there is another computer which works better.' 'OK, then, the reason is that this is the only model that enables me to do all the work I want to do.'

Why did you bother giving the first two arguments, when the third one, the strongest one, would do? That's the same question we can ask about Descartes.

In the first argument, Descartes observes that our senses sometimes deceive us. You offer an interesting though questionable example of this. E.g. 'The sound of rock music is nerve wracking,' 'The sound of rock music is calming.' Two people can have such incompatible beliefs about rock music, based on the different effects that the sound has on their physical and mental constitution. However, there is no disagreement about the experience itself. Both you and your son, e.g., can agree that a particular rock tune lasts 2 minutes 33 seconds, that the speed is, 100 beats per minute, that it begins with four bars of heavy drum beats before the guitars come in and so on. So you are not in disagreement about the 'facts'. You differ in the effect that the sound has on you.

In order to meet the requirements of the argument from illusion, or the fallibility of the senses, we need examples where our experiences lead us to form false beliefs about how things are in the world. Whether we enjoy the experiences or find them irritating is besides the point. Descartes gives an example of seeing a round tower in the distance, which looks square. Your experience leads you to form a false belief, namely that you are looking at a square tower. But Descartes also offers a reply: we use our senses to correct initial impressions! If you get close enough to the tower, there can be no doubt that it is round.

So that isn't a good enough reason for doubting all our beliefs.

So, then, Descartes ups the ante and considers the case of dreaming. Sometimes we think we are awake when we are in fact dreaming. How can we ever be sure that we are not dreaming rather than awake? This is a stronger argument, but Descartes still finds fault with it. Even if I am dreaming, I know that I can use arithmetic, or describe my experiences in terms of concepts. In other words, even if the argument from dreaming casts doubt on some of my beliefs, it doesn't cast doubt on all my beliefs, e.g. that 2+3=5. The experiences we have in dreams are jumbled up assemblies of the experiences we have when we are awake.

Then, finally, he offers the evil demon argument. Doesn't that show that the first two arguments were superfluous? I don't think so. Because the purpose of the first argument is to draw attention to the difference between a subjective, mental perception and an objectively existing thing. The purpose of the second argument is to show that dreams and waking experience are exactly alike insofar as they are constituted by a sequence of subjective, mental perceptions.

Having established these two claims, Descartes is finally in a position to give the knock-out blow. A sufficiently powerful evil demon could produce these subjective, mental perceptions in us, such that we are led to believe in the existence of an external, spatial world when in reality no such world exists. All that exists is me and the evil demon.

I haven't said whether I think that this is a good enough reason to doubt all our beliefs. I leave that for you to think about!

All the best,