Cogito Ergo Sum

Cogito ergo sum (French: "Je pense donc je suis"; English: "I think, therefore I am") is a philosophical Latin statement proposed by René Descartes. The simple meaning of the phrase is that someone wondering whether or not he or she exists is, in and of itself, proof that something, an "I", exists to do the thinking. However, this "I" is not the more or less permanent person we call "I". It may be that the something that thinks is purely momentary, and not the same as the something which has a different thought the next moment.

The phrase became a fundamental element of Western philosophy, as it was perceived to form a foundation for all knowledge. While other knowledge could be a figment of imagination, deception or mistake, the very act of doubting one's own existence serves to some people as proof of the reality of one's own existence, or at least that of one's thought.

The statement is sometimes given as Dubito, ergo cogito, ergo sum (English: "I doubt, therefore I think, therefore I am").

Descartes's original statement was "Je pense donc je suis", from his Discourse on Method (1637). He wrote it in French, not in Latin and thereby reached a wider audience in his country than that of scholars. He uses the Latin "Cogito ergo sum" in the later Principles of Philosophy (1644), Part 1, article 7:

"Ac proinde hæc cognitio, ego cogito, ergo sum, est omnium prima & certissima, quæ cuilibet ordine philosophanti occurrat."

English: "This proposition, I think, therefore I am, is the first and the most certain which presents itself to whoever conducts his thoughts in order."

At that time, the argument had become popularly known in the English speaking world as "the 'Cogito Ergo Sum' argument", which is usually shortened to "Cogito" when referring to the principle virtually everywhere else.