Cogito, ergo sum Cogito, ergo sum This proposition became a fundamental element of Western philosophy, as it purported to form a secure foundation for knowledge in the face of radical doubt. While other knowledge could be a figment of imagination, deception, or mistake, Descartes asserted that the very act of doubting one's own existence served—at minimum—as proof of the reality of one's own mind; there must be a thinking entity—in this case the self—for there to be a thought. Descartes first wrote the phrase in French in his 1637 "Discourse on the Method". He referred to it in Latin without explicitly stating the
Cogito, ergo sum further knowledge; rather, it is the firm ground upon which he can stand as he works to discover further truths 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. (AT VII 24; CSM II 16) According to many Descartes specialists, including Étienne Gilson, the goal of Descartes in establishing this first truth is to demonstrate the capacity of his criterion — the immediate clarity and