René Descartes

René Descartes René Descartes was a French philosopher, mathematician, and scientist who founded modern rationalist philosophy with his Meditations on First Philosophy (1641), in which his famous declaration Cogito, ergo sum ("I think, therefore I am") established subjective consciousness as the bedrock of certainty. He also invented analytic geometry, bridging algebra and Euclidean geometry, and made significant contributions to optics and physiology. Cartesian dualism — the separation of mind and matter — dominated philosophical and scientific discourse for centuries.