René Descartes (1596-1650) was a French philosopher, mathematician, and scientist who is often referred to as the 'Father of Modern Philosophy.' His work laid the foundation for 17th-century continental rationalism, later advocated by Spinoza and Leibniz, and his influence in mathematics is equally profound, particularly with the Cartesian coordinate system that precipitated the development of calculus and analytical geometry. Descartes is best known philosophically for his cogito argument, encapsulated by the famous dictum 'Cogito, ergo sum' ('I think, therefore I am'), found in his 'Discourse on the Method' (1637). His seminal work, 'Meditations on First Philosophy' (1641), continues to be a standard text at most university philosophy departments. Renowned for its methodical and skeptical approach to epistemology, it introduces his method of doubt and the notion of the evil demon as he searches for indubitable truth. In addition to his contributions to philosophy, Descartes' work in mathematics and science, such as 'La Géométrie' (1637), is still integral in academic studies. His correspondences with other intellectuals of his day also provide deep insight into his thought-a man devoted to the pursuit of knowledge through rigorous reasoning and empirical evidence. Descartes' vast literary output and intellectual legacy have immortalized him as a preeminent figure in Western thought.