KNOWLEDGE thinking, therefore I exist’ is undoubtedly a valid argument, whose validity can be taken in at a single mental glance But so too is ‘I am walking, therefore I exist’: so what is special abut the Cogito? Descartes responded that the premiss ‘I am walking’ could be doubted (perhaps I have no body), but the premiss ‘I am thinking’ cannot be doubted, for to doubt is itself to think On the other hand, ‘I think I am walking, therefore I exist’ is a perfectly acceptable form of the cogito: the thinking referred to in the premiss can be a thought of any kind, not just the self-reXexive thought that I exist A more serious question concerns the ‘I’ in ‘I am thinking’ In ordinary life the Wrst-person pronoun gets its meaning in connection with the body that gives its utterance Is someone who doubts whether he has a body entitled to use ‘I’ in soliloquy? Perhaps Descartes was entitled only to say: ‘There is thinking going on.’ Similar questions can be raised about the ‘I’ in ‘I exist’ Perhaps the conclusion should only have been ‘Existing is going on.’ Critics have argued that the doubting Descartes has no right to draw the conclusion that there is an enduring, substantial self Perhaps he should have concluded rather to a Xeeting subject for a transient thought, or perhaps even that there can be thoughts with no owners Is it certain that the ‘I’ revealed by the methodical doubt is the same person who, unpuriWed by doubt, answered to the name ‘Rene´ Descartes’? Even on its own terms, the Cogito does not prove the existence of Descartes as a whole human being By itself, it proves only the existence of his mind After the Cogito Descartes continues to doubt whether he has a body, and it is only after considerable further reasoning that he concludes that he does indeed possess one What he is aware of at all times are the contents of his mind, and it is from these that he must rebuild science From the Cogito, Decartes derives much else besides his own existence: his own essence; the existence of God; the criterion of truth But for our present purposes what is important is to see how he proceeds from this Archimidean point to re-establish the cognitive system that the sceptical arguments appear to have overthrown Cartesian Consciousness The contents of our minds are thoughts ‘Thought’ is used by Descartes very widely: a piece of mental arithmetic, a sexual fantasy, a severe toothache, a 121