Anselm of Canterbury (1033–1109) was a Benedictine monk and teacher who ultimately became the Archbishop of Canterbury, the highest religious office in England. He is the most significant philosopher of his century. He sought to distinguish between philosophy and theology. The famous maxim of Anselm was “Credo ut intelligam,” which means “I believe that I may understand.” Faith comes first; understanding the world around you is secondary and must be infused with faith in order to truly get to the bottom of things.

Anselm continued the faith-based philosophy of Augustine and took it to the next level. He is most famous for his argument which “proves” the existence of God. This argument has fascinated the philosophers that followed Anselm. It is called Anselm's Ontological Argument. The word “ontological” is defined as “Of or relating to the argument for the existence of God holding that the existence of the concept of God entails the existence of God.” In other words, thinking about it makes it so.

Anselm starts off with a quote from Psalm 14: “Fools say in their hearts, ‘There is no god.’” Anselm then says that even a fool can conceive of the notion of something “than which nothing greater can be conceived.” If it can be conceived in the mind of man, it can exist. Even a fool, or a heretic, has some conception of what God might be like. Naturally, for the sake of argument, they called God the most perfect being that could possibly exist. Anselm is suggesting that there is an inherent contradiction in denying the existence of God. In order to deny the existence of God, we must have a conception of what God is. If the limited mind of man can speculate on the existence of so perfect a being, then that said being must in fact exist.