<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> Cogito ergo sum is a Latin philosophical proposition by René Descartes usually translated into English as "I think, therefore I am". The phrase originally appeared in French as je pense, donc je suis in his Discourse on the Method, so as to reach a wider audience than Latin would have allowed . It appeared in Latin in his later Principles of Philosophy . As Descartes explained, "we cannot doubt of our existence while we doubt ..." A fuller form, penned by Antoine Léonard Thomas, aptly captures Descartes's intent: dubito, ergo cogito, ergo sum ("I doubt, therefore I think, therefore I am"). The concept is also sometimes known as the cogito . </P> <P> 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 . </P>

Who said i think therefore i am quote