Discourse on the Method which I did not clearly know to be such." This method of pro-foundational skepticism is considered to be the start of modern philosophy. Discourse on the Method 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"" (English: "I think, therefore I am", or "I am thinking, therefore I exist"), which occurs in Part IV of the work. The similar Latin statement, "Cogito, ergo sum",
Cogito, ergo sum familiar form of the phrase in his 1641 "Meditations on First Philosophy". The earliest written record of the phrase in Latin is in his 1644 "Principles of Philosophy", where, in a margin note (see below), he provides a clear explanation of his intent: "[W]e cannot doubt of our existence while we doubt". Fuller forms of the phrase are attributable to other authors. The phrase first appeared (in French) in Descartes's 1637 "Discourse on the Method" in the first paragraph of its fourth part: In 1641, Descartes published (in Latin) "Meditations on first philosophy" in which he referred to the proposition,