René Descartes (AD 1596-1650) René Descartes is the father of modern philosophy. His famous cogito ergo sum turned the philosophical world on its head, by starting with the individual human subject, rather than with the sensible world. His mathematical approach to philosophy sought clear and distinct ideas and inaugurated a period of great scientific discovery, but did so at the expense of making a definitive break between philosophy and theology. Descartes’ writings are studied by our freshmen in Modern Philosophy, by our sophomores in Philosophy of Nature, and by our juniors in Epistemology.