(This cartoon, while cute, doesn't understand the Ontological Argument. For why Gaunilo's criticism of Anselm's OA does not work, see below.)
For my Philosophy of Religion classes:
The two best philosophical websites are:
We're now studying the Ontological Argument for the existence of God. Go to these websites to the "Ontological Argument" essays.
Note: They are academic essays, not watered down.
NOW... why Gaunilo does not refute Anselm's OA. I quote from the Internet Encyclopedia of Philosophy essay on "Ontological Argument."
"Gaunilo's argument is incoherent. The problem here is that the qualities that make an island great are not the sort of qualities that admit of conceptually maximal qualities. No matter how great any island is in some respect, it is always possible to imagine an island greater than that island in that very respect. For example, if one thinks that abundant fruit is a great-making property for an island, then, no matter how great a particular island might be, it will always be possible to imagine a greater island because there is no intrinsic maximum for fruit-abundance. For this reason, the very concept of a piland is incoherent.
But this is not true of the concept of God as Anselm conceives it. Properties like knowledge, power, and moral goodness, which comprise the concept of a maximally great being, do have intrinsic maximums. For example, perfect knowledge requires knowing all and only true propositions; it is conceptually impossible to know more than this. Likewise, perfect power means being able to do everything that it is possible to do; it is conceptually impossible for a being to be able to do more than this.
The general point here, then, is this: Anselm's argument works, if at all, only for concepts that are entirely defined in terms of properties that admit of some sort of intrinsic maximum. As C.D. Broad puts this important point:
'[The notion of a greatest possible being imaginable assumes that] each positive property is to be present in the highest possible degree. Now this will be meaningless verbiage unless there is some intrinsic maximum or upper limit to the possible intensity of every positive property which is capable of degrees. With some magnitudes this condition is fulfilled. It is, e.g., logically impossible that any proper fraction should exceed the ratio 1/1; and again, on a certain definition of "angle," it is logically impossible for any angle to exceed four right angles. But it seems quite clear that there are other properties, such as length or temperature or pain, to which there is no intrinsic maximum or upper limit of degree.'
If any of the properties that are conceptually essential to the notion of God do not admit of an intrinsic maximum, then Anselm's argument strategy will not work because, like Guanilo's concept of a piland, the relevant concept of God is incoherent. But insofar as the relevant great-making properties are limited to omnipotence, omniscience, and moral perfection (which do admit of intrinsic maximums), Anselm's notion of a greatest possible being seems to avoid the worry expressed by Broad and Guanilo."