Anselm of Canterbury (1033-1109) was one of the originators of medieval scholastic philosophy. This collection of his best-known philosophical works contains, among other things, the Proslogian, in which Anselm first put forward argument for the existence of God. Also included are Gaunilo of Marmoutier's criticism of Anselm's argument and Anselm's argument and Anselm's reply to Gaunilo.