4. Cogito Ergo Sum
4.1 The First Item of Knowledge
Famously, Descartes puts forward a very simple candidate as the first item of knowledge. The candidate is suggested by methodic doubtby the very effort at thinking all my thoughts might be mistaken. Early in the Second Meditation, Descartes has his meditator observe:
I have convinced myself that there is absolutely nothing in the world, no sky, no earth, no minds, no bodies. Does it now follow that I too do not exist? No: if I convinced myself of something then I certainly existed. But 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. (Med. 2, AT 7:25)
As the canonical formulation has it,
I think therefore I am (Latin:
cogito ergo sum; French:
je pense,
donc je suis)a formulation which does not expressly arise in the
Meditations.
Descartes regards the
cogito (as I shall refer to it) as the first and most certain of all to occur to anyone who philosophizes in an orderly way (
Prin. 1:7, AT 8a:7). Testing the
cogito with methodic doubt is supposed to help me appreciate its certainty. For the existence of my body is subject to doubts that the existence of my thinking resist. Indeed, the very attempt at thinking away my thinking is self-stultifying.
The
cogito raises numerous philosophical questions and has generated an enormous literature. In summary fashion, I'll try to clarify a few central points.
First, a first-person formulation is essential to the certainty of the
cogito. Third-person claims, such as Icarus thinks, or Descartes thinks, are not unshakably certainnot for
me, at any rate; only the occurrence of
my thought has a chance of resisting hyperbolic doubt. There are a number of passages in which Descartes refers to a third-person version of the
cogito. But none of these occurs in the context of trying to establish categorically the existence of a particular thinker (as opposed merely to the conditional existence of whatever thinks).
Second, a present tense formulation is essential to the certainty of the
cogito. It's no good to reason that I existed since I recall I was thinking, because methodic doubt calls into question whether I'm having veridical memories. (Maybe I'm merely dreaming that I was thinking, or maybe an evil genius is feeding me false memories.) Nor does it work to reason that I shall continue to exist since I am now thinking. As the meditator remarks, it could be that were I totally to cease from thinking, I should totally cease to exist (Med. 2, AT 7:27). The privileged certainty of the
cogito is grounded in the manifest contradiction (cf. AT 7:36) of thinking away my occurrent thinking.
Third, the certainty of the
cogito depends on being formulated in terms of my
cogitatioi.e., my thinking, or awareness/consciousness more generally. Any mode of my thinking is sufficient: doubt, understanding, affirmation, denial, volition, imagination, sensation, or the like (cf. Med. 2, AT 7:28). My non-thinking activities, on the other hand, are insufficient. For instance, it's no good to reason that I exist since I am walking, because methodic doubt calls into question the existence of my legs. (Maybe I'm just dreaming that I have legs.) A simple revision, such as I exist since it
seems I'm walking, restores the anti-sceptical potency (cf. Replies 5, AT 7:352;
Prin. 1:9).
(btw, I make a keen distinction between common sense and logic and so do not use the two interchangeably like most people I know do.)
