The Ontological Argument

Abstract The term “ontological argument” was Kant's name for one member of a family of arguments that began with Anselm of Canterbury. These arguments all try to prove God's existence a priori, via reasoning about the entailments of a particular description of God. The description almost always involves God's greatness or perfection. Where it does not, the argument has a premise justified by God's greatness or perfection. So these arguments might better be called arguments from perfection. This article deals with the main arguments from perfection and criticisms thereof in historical order. It first explicates Anselm's key phrase “something than which no greater can be thought” and then takes up his reasoning, then the question of whether its premises are true.