(3) Cogito Ergo Sum
(A) Descartes First Principle
There are three main passages where Descartes enunciates his first principle:
(a) . . . I noticed that while I was trying . . . to think everything false, it was necessary that I, who was thinking this, was something. And observing that this truth I am thinking, therefore I exist was so firm and sure that all the most extravagant suppositions of the sceptics were incapable of shaking it, I decided that I could accept it without scruple as the first principle of the philosophy I was seeking. [Discourse IV, para. 1; CSM, I, p. 127.]
(b) But [on the most radical sceptical hypothesis] there is a deceiver of supreme power and cunning who is deliberately and constantly deceiving me. In that case I too undoubtedly exist, if he is deceiving me; and let him deceive me as much as he can, he will never bring it about that I am nothing so long as I think that I am something. So after considering everything very thoroughly, I must finally conclude that this proposition, I am, I exist, is necessarily true whenever it is put forward by me or conceived in my mind. [Meditations II, para. 3; CSM, II, p. 17.]
(c) . . . we cannot for all that [we might doubt] suppose that we, who are having such thoughts, are nothing. For it is a contradiction to suppose that what thinks does not, at the very time when it is thinking, exist. Accordingly, this piece of knowledge - I am thinking, therefore I exist is the first and most certain of all to occur to anyone who philosophizes in an orderly way. [Principles I, section 7; CSM, I, pp. 194-5.]
(B) Interpretations and Issues
(1) Intuition or deduction?
The famous proposition Cogito ergo sum does not occur in the Meditations passage, suggesting that it is not, at least, a straightforward inference. Descartes himself denies that it is a syllogism (with a suppressed premiss):
Yet there is clearly some argument involved, I exist being some kind of conclusion, arrived at as a result of Descartes sceptical considerations. By intuition here, Descartes doesnt just mean a recognition of something as true, but a recognition of something as certain; so that we can say that what is being intuited is the certainty of ones own existence, on the basis of the sceptical argumentation.
(2) Implicit knowledge
The passage from the 2nd Replies also raises a problem about the role of general principles. Elsewhere, Descartes states:
Descartes is not denying that, in some sense, we know the general principle; what he wants to argue is that it is not our knowledge of this that makes us certain of our own existence. However, there does seem to be a tension between this view and the implications of Descartes initial sceptical considerations, where it seems to be suggested that such general propositions can indeed be doubted. Such a view also seems in conflict with the transparency doctrine noted below.
(3) What kind of thinking?
Thinking, according to Descartes, covers any kind of mental activity, so would any kind of thought do as a premiss for the Cogito? There are passages that seem to suggest this, a view that emerges naturally out of his so-called doctrine of the perfect transparency of the mind, thoughts being whatever we are aware of as happening within us (see Principles, I, 9). But this seems to make the emergence of the Cogito conclusion out of the sceptical considerations problematic, it being the specific process of doubting that makes us certain of our own existence. There may thus again be a certain tension between proving the truth of the Cogito conclusion, and demonstrating its certainty.
(4) Inference or performance?
Hintikka has argued that there are two lines of thought involved in the Cogito. The first amounts to an inference that I exist from the premisses that if I am right in thinking something, I must exist, and that if I am wrong in thinking something, I must still nevertheless exist (to be wrong). But, he writes:
However, it is open to us to simply deny the initial premiss of this argument (if there was no Homer, the premiss is neither true nor false); and to the general charge of petitio principii, Descartes might respond that he is making explicit our knowledge of our own existence, so that we can be certain of it.
On Hintikkas second interpretation, the Cogito is construed as a performance, the very act of thinking that I exist (or wondering whether I exist) demonstrating its truth. It is the existential self-verifiability of I exist that provides the required indubitability when I follow the Cogito line of thought (cf. ibid., pp. 121-2). However, it is hard to reconcile this interpretation with Descartes texts. In particular, it is not the thought that I exist that is pivotal in his reasoning, and the relationship to his sceptical considerations is rendered unclear.
(5) What am I?
If Cogito ergo sum is some kind of argument, then Cogito is its premiss. But what exactly does this involve? It has often been argued that all Descartes is entitled to is the premiss there is some thinking going on. Lichtenberg, for example, wrote: We should say it thinks, just as we say it lightens. To say cogito is already to say too much as soon as we translate it I think. To assume, to postulate the I is a practical requirement. [Aphorisms, tr. R.J. Hollingdale, Penguin, 1990, p. 168.] To conclude I am, then, might seem of little content; yet Descartes wants to move from Cogito ergo sum immediately to Sum res cogitans, which arguably provides a significant addition to Sum. Here the move is supported by appeal to the principle nihili nulla sunt attributa (nothing can be predicated of nothing; cf. e.g. Principles, I, 11), resting on the Aristotelian doctrine of substance and attribute. If there is a thought, then there must be a thinker having it. But what is it to be a thinker?
© Mike Beaney
Early Modern Philosophy