Latest version of my SEP entry on ontological arguments, which first appeared in 1996. General discussion of ontological arguments. Includes a brief historical overview, a taxonomy of different kinds of ontological arguments, a brief survey of objections to the different kinds of ontological arguments identified in the taxonomy, and more extended discussions of Anselm's ontological argument (Proslogion 2), Godel's ontological argument, and Plantinga's ontological argument.

This paper is a defense of the view that existence is a perfection. Anselm’s First Ontological Argument is referred to throughout. Two major objections are advanced: the ‘perfect island’ objection and the ‘perfect devil’ objection. A rebuttal of both, based on Anselm’s reply to Gaunilo, is tendered, but itself faces a major objection. Two lines of defense against this objection are possible. The first is sympathetically explained but it is argued that it ultimately fails. The second, which focuses on the (...) idea of a perfection and a perfect being, is elaborated and defended against a seemingly powerful objection. It is concluded that there is a reasonable interpretation of the claim that existence is a perfection. (shrink)

This paper reconstructs and discusses a proof of God’s existence by Anselm of Canterbury’s friend Ralph of Battle, developed in his recently edited De nesciente, a fictitious dialogue between a Christian and an atheist. Without precedent in antiquity and the Middle Ages, Ralph’s proof has never been examined in detail. It combines a “cogito” argument with a two-part cosmological argument. The paper first presents the textual basis and an exegetical interpretation of Ralph’s reasoning, classifies the parts of the proof historically (...) and systematically, and then compares these with the proofs of God’s existence as well as other arguments in Anselm’s Proslogion and Monologion. Finally, it points out some similarities between Ralph’s “cogito” argument and a passage in the Liber pro insipiente, which may suggest that this anonymous critique of Anselm’s Proslogion proof was authored not by Gaunilo, as traditionally thought, but by Ralph. (shrink)