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Descartes' argument for the mind-body distinction


To: Emelie G.
From: Geoffrey Klempner
Subject: Descartes' argument for the mind-body distinction
Date: 8th December 2011 11:55

Dear Emelie,

Thank you for your email of 4 December, with your essay for the University of London BA Modern Philosophy: Descartes, Locke, Berkeley and Hume module, in response to the question, 'What did Descartes mean when he said that there is a real distinction between the mind and the body? Describe and critically evaluate the arguments he gave for this thesis.'

This is an excellent piece of detective work, in which you make every effort to uncover the basis for Descartes' claim that there is a real distinction between the mind and the body, in order to evaluate the validity of his argument.

As you state, the matter is left open in Meditation 2 (or, at least, that is what Descartes concedes to Hobbes), and it is not until Meditation 6 that Descartes considers that he is in a position to offer a definitive argument. As you comment, 'And this must mean that God must be involved.' Yet, what Descartes actually says in the important passage is that two things are separate if it is possible in principle for them to be separated, 'if only by the power of God'.

The objection you raise to this is that if the eternal truths are 'products of God's will' then there are lots of things God can do, such as create 'a square apart from four sides'. In other words, if the connection between mind and body is as close as the connection between a square and four sides, that is as close as anyone would wish to get to a proof of monism, God notwithstanding.

Did Descartes think that God could create a square without four sides? Frankly, I don't know what this would mean and I don't think Descartes did either. However, this is missing the point in a sense. Two things which we cannot separate might yet be separate in reality, i.e. logically distinct, if they can, in principle be separated by an agency with greater powers; and perhaps only God fits that description (or perhaps not, maybe there is room for an evil demon in the actual world).

The reason a proof of God is needed is rather that we need assurance that what we perceive 'clearly and distinctly' is true. Excellent point. I don't think however that the Cartesian Circle is sufficient to rebut this claim. There is a difficulty, to be sure. However, the Cartesian Circle is not a knock-down argument. And I don't think that an essay on the real distinction between mind and body should require you to defend your view on the Cartesian Circle. That would be a suitable topic for another essay.

I also liked your point about Descartes' claim that his essence as a mental substance is thinking, on the grounds that he cannot conceive of himself as not thinking. Why not run the very same argument substituting 'existing' for 'thinking'?!

It is relevant here to point out that Descartes himself raised the question, what exactly does happen to the soul when you are asleep? To my recollection, he doesn't have a definitive answer to this. The soul, as a unitary substance, cannot just go out of existence and come back again.

Your introduction of the idea of a 'third-person' perspective is crucial, because nowhere in the Meditations (or in any of his other writings, to my knowledge) does Descartes consider the sceptical hypothesis that there might be *nothing* besides myself, not even an evil demon giving me my experiences. There is something, which is my essence, which manifests itself as various modes of thinking (when I am awake) that also exists for the 'third-person perspective' of God, or an evil demon. This can be used to give sense to the idea that I still exist while I am asleep. The question of 'other minds' (hence, the 'third-person' perspective of materialism, cf. Nagel's criticism of this view in 'What is it Like to be a Bat?') doesn't come into it.

It is because Descartes never doubts the existence of an 'objective' view of the mind as essentially thinking substance that it is difficult or impossible to deploy Wittgenstein's argument against a private language, which (in my view, also Daniel Dennett's) is lethal against contemporary varieties of dualism that assume the existence of 'private objects' having a subjective side but no objective side. Something with the power of God (or an evil demon) could create me and 'my world' in the absence of a world of extended matter.

Berkeley was sufficiently impressed by that argument to conclude that idealism is the only coherent metaphysical theory. Because if 'what God has to do' to create me and my world includes creating other subjects of experience, and all the objects of our experience, then there simply is no extra task which consists in 'creating extended substance'. The job has already been done.

Whereas Descartes would say that in that case we *are* deceived. We think, talk and act 'as if' there is an external world (just as Kant argues we must in his 'Refutation of Idealism') but there is nothing 'out there' corresponding to our beliefs, just more of the same ('ideas').

If this is correct, then Descartes' real argument is with Berkeleian idealism, not with materialism. Arguably, the dualism this leads to is not a dualism of mind and body, but rather the Kantian dualism of phenomena and noumena. But that's another story.

All the best,



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