[dey-kahrt; Fr. dey-kart] 
| Re⋅né [ruh-ney; Fr. ruh-ney] , 1596–1650, French philosopher and mathematician. |
| Des·cartes (dā-kärt') French mathematician, philosopher, and scientist who is considered the father of analytic geometry and the founder of modern rationalism. His main works, Meditations on First Philosophy (1641) and Principles of Philosophy (1644), include the famous dictum "I think, therefore I am." |