Anselm of Canterbury

Anselm of Canterbury was a Benedictine monk, Archbishop of Canterbury, and one of the most important philosopher-theologians of the early medieval period. He is best known for his ontological argument for the existence of God, set out in the Proslogion: if God is "that than which nothing greater can be conceived", then God must exist in reality as well as in the understanding, since a God who existed in reality would be greater than one who existed only as a concept.