In the Proslogion, St. Anselm presents a philosophical argument for the existence of God. Anselm's proof, known since the time of Kant as the ontological argument for the existence of God, has played an important role in the history of philosophy and has been incorporated in various forms into the systems of Descartes, Leibniz, Hegel, and others. Included in this edition of the Proslogion are Gaunilo's "A Reply on Behalf of the Fool" and...