Descartes: Discourse on Method Notes by Dr. Honora M. Finkelstein René Descartes developed a four-part method of deductive reasoning. The four steps in the Cartesian series are as follows: 1. To accept nothing as true except that which by reason or direct knowledge he could be assured of without doubt 2. To divide each problem into parts 3. To solve each part in an orderly fashion, moving form the simplest to the more complex 4. To check the results to be sure nothing has been left out The first principle of Cartesian philosophy developed as follows: while he was attempting to think everything false, it occurred to him that he, as the thinker, must exist, or as the premise is often stated, "Cogito, ergo sum"—"I think, therefore I am." From this first premise, which could not be refuted, he had the first principle he needed to derive the existence of the rest of the universe, and even of God. Made with Xara Website by Susan Smily