Gaunilo’s Lost Island Objection to Anselm’s Ontological Argument aims to show that if Anselm’s argument can establish the existence of a greatest conceivable being then a very similar argument can establish the existence of a greatest conceivable island. The challenge for the defender of Anselm is to identify the relevant disanalogy between Anselm’s argument and Gaunilo’s, in order to explain why Anselm’s can succeed while Gaunilo’s fails. In this essay I take up this challenge. Reflection on the differences between the (...) nature of islands and the nature of being yields the relevant disanalogy. (shrink)