Cogito ergo sum

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Cogito ergo sum

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The Latin phrase cogito ergo sum ( "I think, therefore I am") is a philosophical proposition by René Descartes.


Interpretation

The phrase cogito ergo sum is not used in Descartes' Meditations on First Philosophy but the term "the cogito" is used to refer to an argument from it. In the Meditations, Descartes phrases the conclusion of the argument as "that the proposition, I am, I exist, is necessarily true whenever it is put forward by me or conceived in my mind." (Meditation II)

At the beginning of the second meditation, having reached what he considers to be the ultimate level of doubt — his argument from the existence of a deceiving god — Descartes examines his beliefs to see if any have survived the doubt. In his belief in his own existence, he finds that it is impossible to doubt that he exists. Even if there were a deceiving god (or an evil demon), one's belief in their own existence would be secure, for there is no way one could be deceived unless one existed in order to be deceived.

But 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 [or thought anything at all], then I certainly existed. But there is a deceiver of supreme power and cunning who deliberately and constantly deceives me. In that case, I, too, undoubtedly exist, if he deceives 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 the proposition, I am, I exist, is necessarily true whenever it is put forward by me or conceived in my mind. (AT VII 25; CSM II 16–17)

There are three important notes to keep in mind here. First, he claims only the certainty of his own existence from the first-person point of view — he has not proved the existence of other minds at this point. This is something that has to be thought through by each of us for ourselves, as we follow the course of the meditations. Second, he does not say that his existence is necessary; he says that if he thinks, then necessarily he exists (see the instantiation principle). Third, this proposition "I am, I exist" is held true not based on a deduction (as mentioned above) or on empirical induction but on the clarity and self-evidence of the proposition. Descartes does not use this first certainty, the cogito, as a foundation upon which to build further knowledge; rather, it is the firm ground upon which he can stand as he works to restore his beliefs. As he puts it:

Archimedes used to demand just one firm and immovable point in order to shift the entire earth; so I too can hope for great things if I manage to find just one thing, however slight, that is certain and unshakable.



- posted by H.V.O.M - Kerry Wayne Burgess 2:13 PM Pacific Time near Seattle Washington State USA Monday 05 August 2013