Descartes, RenéDes‧cartes, Re‧né /ˈdeɪkɑːt $ deɪˈkɑːrt, reˈneɪ/ 
(1596–1650) a French mathematician and philosopher famous for establishing the principle of ‘cogito ergo sum’ (=I think, therefore I am), that is, I know that I exist because I know that I think
(1596–1650) a French mathematician and philosopher famous for establishing the principle of ‘cogito ergo sum’ (=I think, therefore I am), that is, I know that I exist because I know that I think