Medieval Philosophy

by Peter S. Adamson

which a greater cannot be thought to be eternal, because if it were not eternal, we could think of something better: we need just think of something that is eternal. In the same way, it is implied by the formula that the thing in question must exist, because if it didn’t exist, we could conceive of something better than it. The Fool must therefore admit that God exists, on pain of contradicting himself. Like Mr T, Gaunilo pitied the Fool, and argued on his behalf that Anselm’s argument fails. He devised a number of objections, including his famous island analogy (On Behalf of the Fool §6). Consider, says Gaunilo, an island than which no better island can be conceived. If we supposed that this island didn’t exist in reality, we would fall into the same contradiction, because a non-existing island clearly isn’t one than which no better island can be conceived. Therefore, such an island in fact exists. Gaunilo’s objection is a powerful one. If you can use a pattern of reasoning to prove something false, then you know there is something wrong with that pattern of reasoning.