René Descartes

Descartes, René (1596–1650), French mathematician, scientist, and philosopher, often referred to as “the father of modern philosophy.” A dualist who believed the world was composed of 2 basic substances (matter and spirit), he ignored accepted scholastic philosophy and stated a person should doubt all sense experiences; but if a person can think and doubt, he or she therefore exists. Descartes stated this belief in his famous phrase, cogito, ergo sum (“I think, therefore I am.”) This skeptical philosophy is called Cartesianism and is detailed in Descartes's Meditations on First Philosophy (1641). His other major works include the Discourse on Method (1637) and Principles of Philosophy (1644). Descartes also attempted to explain the universe in terms of matter and motion and invented analytic geometry.

See also: Philosophy.