René Descartes

René Descartes (1596–1650) was a French philosopher, mathematician, and scientist whose work shaped both modern philosophy and the study of geometry. His best-known books are Discourse on Method and Meditations on First Philosophy, which set out his approach to systematic doubt and reason. He joined geometry and algebra into analytic geometry, and the Cartesian coordinate system is named after him. Descartes also wrote the Passions of the Soul, a treatise on the emotions.