Cogito ergo sum: Encyclopedia II - Cogito ergo sum - Introduction

Cogito ergo sum - Introduction

The phrase "cogito ergo sum" is not used in Descartes' most important work, the Meditations on First Philosophy, but the term "the cogito" is (often confusingly) used to refer to it. Descartes felt that this phrase, which he had used in his earlier Discourse, had been misleading in its implication that he was appealing to an inference, so he changed it to "I am, I exist" (also often called "the first certainty") in order to avoid the term "cogito".

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 has survived the doubt. In his belief in his own existence he finds it: it is impossible to doubt that he exists. Even if there were a deceiving god (or an evil demon, the tool he uses to stop himself sliding back into ungrounded beliefs), his belief in his own existence would be secure, for how could he be deceived unless he existed in order to be deceived?

There are two important notes to keep in mind here. First, he only claims 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. Secondly, he is not saying that his existence is necessary; he is saying that if he's thinking, then he necessarily exists (see the instantiation principle).

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:

Perhaps what Descartes meant, simply put is "I am vividly aware of my existence".

Adapted from the Wikipedia article "Introduction", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki