Source
Discourse on the Method
René Descartes's short work, published in French in 1637, describing how he sought certain knowledge by doubting everything that could be doubted. Part IV contains the famous 'I think, therefore I am'.
References
Quotes (2)
“My third maxim was to endeavor always to conquer myself rather than fortune, and change my desires rather than the order of the world.”
— René Descartes, Discourse on Method (1637), Part III, tr. John Veitch“I think, therefore I am (COGITO ERGO SUM).”
— René Descartes, Discourse on Method (1637), Part IV, tr. John Veitch