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Descartes' argument for mind-body dualism


To: Paul M

From: Geoffrey Klempner

Subject: Descartes' argument for mind-body dualism Date: 16 January 2004 10:07

Dear Paul,

Thank you for your e-mail of 4 January, with your first University of London timed essay, in response to the exam question, 'How does Descartes argue in the sixth meditation that mind and body are distinct substances? Does he succeed in establishing this conclusion?'

As an exam paper this is very well organized, clearly written and persuasive. Frankly, I never wrote an exam answer like this. Because of the quality of the writing, an examiner *might* assume that you were reproducing a previously memorized answer rather than thinking 'on your feet' - this would depend on the quality of your other answers. (There is no rule prohibiting this - but you need to be very lucky with your question.) Of course you had the opportunity to type it out, which would have involved some tidying. For example, I do not see any sentences or paragraphs crossed out!

You said in your afterthoughts that you were 'essentially concerned with the logical consistency of D's argument itself...'. However, my reading of the question is that there is scope - and indeed the necessity - of considering the truth of the premisses of D's argument, and not just whether the conclusion follows from the premisses. The crucial premiss concerns self-knowledge: that knowledge of my own subjective states is independent of my knowledge of the external world. Along with many contemporary philosophers I would regard Wittgenstein's private language argument as a fatal objection to that view. So I think that despite the quality of the essay, this omission would lose marks.

I fully agree with you that God is not required in order to account for the possibility separating mind and body. What is in question is simply whether they can be logically conceived as existing apart. (I did initially get the contrary impression from your statement 'This can only be done after the proof of God's existence...' in paragraph 1. When you go on to say, '...and that everything we clearly and distinctly understand is true...' this *reads* as a second point whereas what you mean is that according toDescartes God's existence is *required* in order for us to be fully confident that everything we clearly and distinctly understand etc. etc.)

AlthoughDescartes does not actually say this in so many words, the argument in Meditation 6 does depend on the claim, made back in Meditation 1, that my knowledge of my subjective states is such as could obtain even in a world where no physical objects existed. This is crucial for understanding Arnaud's objection. For what Descartes seems to be arguing is:

I can know that I exist even if I don't know that my body exists. Therefore, my mind can exist even if my body does not exist.

A better counter-example than Pythagoras would have been:

I can know that George Orwell exists even if I don't know that Eric Blair exists. Therefore, George Orwell can exist even if Eric Blair does not exist.

That is false because George Orwell *is* Eric Blair.

What this shows is that D's argument does not depend on non-substituitivity in opaque contexts, such as 'knows that'.

So, yes, for this reason it is relevant to mention Arnaud, although it would be fully acceptable to consider the point about opaque contexts without mentioning Arnaud as the source of the objection.

All the best,