Anselm's Proof provides a new analysis and a thorough defence of the first "ontological" argument for God's existence, given by Anselm in his Proslogion. It shows that Anselm's background ontology is Meinongian, how to read the argument in light of this, and that Anselm's argument is logically valid. It also demonstrates that one can retool the argument without its Meinongian ontology and preserve its validity. The volume then rebuts all extant objections to the argument. Many accuse the argument of begging the question, but Anselm's Proof considers a wide variety of views of what it is to beg the question, and shows that Anselm's argument does not do so on any good understanding of this fallacy. Many dismiss Anselm's argument by offering parodies which "prove" the existence of various entities. Anselm's Proof provides a detailed, thorough discussion of parody objections, contending that no parody of the Proslogion argument succeeds in showing it to be a bad one. Many have thought that Kant's dictum that "existence is not a predicate" is the death-knell of all "ontological" arguments, but Anselm's Proof shows that Kant's claim is just irrelevant to Proslogion. The volume also acquits the Proslogion argument of charges by Aquinas and current Meinongians. The upshot is that no objection so far brought defeats the Proslogion argument. Anselm's Proof also provides support for two of the Proslogion argument's three premises. Thus if Anselm's Proof is correct, the success of Anselm's project hinges entirely on how well one can support the final premise.