Discourse on the Method of Rightly Conducting One's Reason and of Seeking Truth in the Sciences is a philosophical and autobiographical treatise published by René Descartes in 1637. It is best known as the source of the famous quotation "Je pense, donc je suis" ("I think, therefore I am", or "I am thinking, therefore I exist"), which occurs in Part IV of the work. A similar argument without this precise wording is found in Meditations on First Philosophy, and a Latin version of the same statement, "Cogito, ergo sum", is found in Principles of Philosophy. (Wikipedia, CC BY-SA 4.0)