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What does Descartes' Cogito establish exactly?


To: Neil G.
From: Geoffrey Klempner
Subject: What does Descartes' Cogito establish exactly?
Date: 24th September 2008

Dear Neil,

Thank you for your email of 16 September, with your essay in response to the University of London Modern Philosophy question, 'What exactly did Descartes suppose that the Cogito established? Does it succeed?'

This is another very good essay. I like the clear and articulate way in which you detail the different claims involved in the Cogito, and also succeed in highlighting the subtle difference between the formulations of the Cogito in the Discourse and in the Meditations.

The question whether Descartes is essentially a thinking thing and only contingently a physical thing is one that Descartes returns to in the sixth Meditation. I agree with you that the argument as it stands looks like a non-sequitur. And in fact not much is added in the sixth Meditation. However, Descartes does insist there that whatever can be conceived as separate can be created separately by God, which a non-theist can interpret as the claim that what can be conceived as separate can exist separately in reality.

This suggests that it might be a worth while exercise to look for an additional premiss or premisses which would make the three line argument you have given more convincing.

Let's look at the argument again:

1. It is possible to doubt the existence of my body.

2. The Cogito has demonstrated that I exist for certain, whenever I think.


3. I am essentially a thinking thing and do not depend on the body for my existence.

Let's try interpolating the following step between 1. and 2:

1a. There exists (therefore) a possible world in which I do not have a body.

This does not follow logically from 1. Descartes still needs to show that my doubt that I have a body is a propositional attitude directed towards a consistent, coherent content, a state of affairs which can be realized in some possible world.

However, let's assume for the sake of argument that Descartes has done enough to show this. It seems that a critic could still argue that the fact that, *in some possible world* I do not have a body still does not entail non-identity of my self and my body. In this world, my self and my body are one and the same.

This is the thesis notoriously held by the Australian materialists, Armstrong and Smart and attacked by Saul Kripke in his 1972 paper 'Naming and Necessity' (Blackwell 1980). Kripke is defending a theorem in modal logic according to which from A=B we can infer that necessarily (A=B), i.e. A=B in all possible worlds. Armstrong and Smart argued, on the other hand, that materialism is simply a consequence of Occam's Razor. It is conceivable that mind and body are not identical, but that hypothesis multiplies entities unnecessarily.

My own view (for what it's worth) is that Kripke was right about this, in which case all our efforts have to be focused on attacking 1a.

Let's move on to the question whether Descartes has succeeded in proving that he is a 'being that thinks'.

I agree with your conclusions here, which have been echoed by many philosophers. Perhaps the most interesting angle comes from Kant, in the 'Paralogisms of Transcendental Psychology' from the second part of his 'Critique of Pure Reason', where Kant accuses Descartes of mistaking the 'perception of unity' for the transcendental 'unity of apperception'. Kant considers a scenario where 'my' thoughts are shared by a succession of momentary selves, each of which transmits its states to the next like a line of colliding billiard balls.

What this argument shows, or claims to show, is that contra Descartes the self or I does not denote a substance. However, Kant accepts and endorses the idea of the 'I think' which accompanies all perceptions. We cannot even talk of perceptions or mental contents without referring them to a notional subject, the 'transcendental ego'.

This agrees with your conclusion that, 'the Cogito stated in the Second Meditation is more resistant to Russell's criticisms.' Thoughts are not entities that can exist except as 'I-thinks'. What still needs to be said, however, is how the reference to a subject is even possible, a task which for Kant involves proving the very thing that Descartes held in doubt: the existence of a world outside my subjective experiences.

All the best,