Des ‧ cartes, Re ‧ né /ˈdeɪkɑːt $ deɪˈkɑːrt, reˈneɪ/ BrE AmE
(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