I argued here that it is possible that a perfect being exists. The argument is as follows (for a defense of the argument, see the above link):
(1) It is false that being perfect entails being evil.
Assume for reductio that
(2) Being perfect is necessarily uninstantiated.
Since a necessarily uninstantiated property trivially entails any property,
(3) Then being perfect entails being evil.
Since (1) and (3) are incompossible, we must reject our assumption. Hence,
(4) Therefore, it is false that being perfect is necessarily uninstantiated.
Gaunilo famously rejected St. Anselm’s ontological argument on the basis of his island parody. Perhaps he might have similarly argued against the above argument. Let us say that an island-perfection (IP) is one whose instantiation adds to, but does not subtract from, the greatness of any island in which it inheres, and let us say that being a perfect island just is the conjunction of all IPs. The parody is as follows.
(1*) It is false that being a perfect island entails P, where P is an island-imperfection.
Assume, for reductio, that
(2*) Being a perfect island is necessarily uninstantiated.
(3*) Being a perfect island entails P.
(1*) and (3*) are incompossible, so we must reject our assumption. Hence,
(4*) It is false that being a perfect island is necessarily uninstantiated.
Does this parody successfully refute the argument for the possibility of the existence of a perfect being? It seems to me that it does not. Perhaps it is possible that a perfect island exists. Possibility claims are very usually innocuous, so it seems to me that one can reasonably admit that both arguments are sound. A problem arises only when the person who advances the parody attempts to argue from (4*) to
(5*) A perfect island exists.
But the inference from (4*) to (5*) is valid only if
(6*) Being a perfect island entails being necessarily existent
is a necessary truth. But I see no good reason whatever to grant (6*) and very good reason to grant (7*):
(7*) Being an island entails being contingent.
Several reasons can be given to prefer (7*) over (6*) that do not at all apply to perfect beings, which, if right, entails that the parody fails, for we have reasons to reject it that do not apply to the parodied argument. First, following Plantinga, let us say that a state of affairs S includes a state of affairs S* just in case it is impossible that S obtain and S* fail to obtain. Now, being an island entails being a material being. This strongly suggests that (7*) is true, for it is certainly possible that nothing material exists, in which case there is at least one possible world in which there are no islands, which is enough to falsify (6*). Interestingly, there is good scientific evidence to suppose that space and time began to exist. Since the existence of space and time are necessary conditions of the existence of material things, including islands, this entails that there is a possible state of affair that does not include the state of affair consisting in the existence of an island, or anything material. So there is a world W in which no islands exist.
Moreover, if (6*) is true and being a perfect island is possibly instantiated, then it follows that, in the actual world, a perfect island exists in a timeless state. For its having the property being necessary entails that it is impossible that it fail to exist and, given that time began to exist, the island would have to exist sans time. But clearly this is impossible. So the conclusion is that (6*) is false and that (7*) is true.
It seems to me, therefore, that this parody fails. The reasons for supposing that the parody is unsound do not at all apply to perfect beings.
*Thanks to the blogger at Vexing Questions for his helpful suggestions. You can find his blog here. I also wish to thank someone whose name shall remain anonymous for bringing this parody to my attention.