So far we’ve tried two attempts to show that theism is theoretically rational. Our first attempt required that we assume that the only pos-sible explanation of the complexity and apparent design in the world is that it was made by an intelligent, sentient designer. This assumption
seems questionable because there is another possible explanation: the theory of evolution by natural selection. We then noticed that for ENS to be so much as possible, matter would have to exist. Where could that matter come from? That question forms the basis of the cosmological argument. We’ve found that this argument runs into trouble once we consider the possibility that the chain of events forms an infinite causal regression.That may seem unlikely, but it is possible, and the proponent of the cosmological argument has no way of rul-ing it out. Samuel Clarke makes an rul-ingenious attempt to show that even if there is an infinite causal regression, there still has to be an independent being. However, we found no reason to think his argu-ment sound.
Might there be another way to show that theism is theoretically rational? Here is an argument attempting to show that from the very concept of the GCB we may infer that God exists. We know that by definition God is the GCB. Being the greatest conceivable implies that one has all possible perfections: If there is a perfection that a being lacks, then that being is not the greatest conceivable.
Furthermore, at least for things that are good, it would seem that they are more perfect if they exist than if they don’t. For instance, imagine your dream date, the most wonderful person you can imagine going out with.You get to pick the person’s gender, hairstyle, hobbies, musi-cal tastes, and so forth. Now suppose someone tells you,“There’s only one little problem.To the best of our knowledge that person does not exist.” You’d be disappointed. You would probably think that dream dates would be even more wonderful if they existed. If so, then haps this is enough to get you to see that good things are more per-fect if they exist than if they do not exist.3 Now we have all the premises that we need for the ontological argument:
1. God is the GCB.
2. God has all possible perfections.
3. Existence is a perfection.
4. God has the property of existence, 5. God exists.
Premise 1 just states a definition. It does not assume that “God” refers to anything. In fact, none of premises 1–4 assumes that “‘God” refers to
The Greatest Conceivable Being 43
ergo,
3I owe this example to Richard Gale.
anything at all. Those lines of the argument just spell out the defini-tion of the GCB and the consequences of that definidefini-tion.We owe this argument to Saint Anselm (1033–1109), a theologian and philosopher who was also Archbishop of Canterbury. Anselm summarizes this line of thought by saying that so long as the GCB exists in your under-standing, that is, so long as you can form a coherent idea of the GCB, you must acknowledge that the GCB exists in reality as well.
A monk who was a contemporary of Anselm’s, Gaunilo, held that this argument must have gone wrong somewhere. Gaunilo’s point was that if the argument was a good one, it could just as easily be used to prove the existence of a Greatest Conceivable Island. After all, a GCI has all possible islandly perfections, such as maximally white sand, per-fect surfing waves, delicious coconuts, and so forth. So too, it would be better for that island to exist than for it not to exist. It is easy to see how the conclusion would follow. Gaunilo’s point, then, is that if Anselm’s argument were any good, it would also prove the existence of the GCI; but of course there is no such GCI. Hence, Gaunilo con-cludes, Anselm’s argument is no good.
Gaunilo in effect lampoons Anselm’s argument without quite put-ting his finger on where Anselm’s argument goes wrong. Moreover, Anselm eventually found a reply to Gaunilo by pointing out that unlike the concept of a GCB, the concept of a GCI is in fact not well defined. Let’s return to that island. Unlike God, the island is a physi-cal object with quantitative, not just qualitative features. However, maximal perfection does not seem to make sense for something with quantitative features. To see why, notice that for any number N of grains of sand on the imagined island, for instance, the island would be even greater if it had just one more, N+1; likewise for palm trees, coconuts, and surfable waves. Anselm’s point is that the GCI is not well defined, just as the concept of the largest integer is not well defined. By contrast, we have, at least thus far, no reason to doubt that the concept of the GCB is well defined. (Later in this chapter we dis-cuss the paradox of the stone, which does raise this doubt.)
Anselm, then, seems to fend off Gaunilo’s challenge. Should we be convinced, therefore, by his argument? Many people have been con-vinced of it. I suggest that we do well to scrutinize the idea that existence is a perfection. After all, the “dream date” example might be challenged. While it might be better for you if your dream date exists, that does not show that existing makes the person in question more perfect. (Consider this case: A Goth-rock Satan-worshiper
might justifiably feel that it would be better for them if Satan existed. However, this wouldn’t prove the existence of the Greatest Conceivable Evil Being.)
Perhaps, then, it is not so clear that existence is a perfection.
Instead, another way of formulating an ontological argument begins with the thought that the GCB is possible. Most nontheists will be happy to agree that it is possible that the GCB exists.Yet, the theist will now point out, a GCB couldn’t just exist in some possible situa-tion. If the GCB were to be merely possible, it would then be con-tingent, subject to outrageous fortune—thus not the greatest conceivable. Instead, to be the Greatest Conceivable, the GCB would have to exist not just possibly, but necessarily. But, of course, if a being exists necessarily, then we can be quite sure that it exists. Hence, if the GCB is possible, then it is necessary and thus actual.
That’s a big “if.”A skeptic might have reasons for doubting that the GCB really is possible. Perhaps contradiction lurks in the very con-cept of the GCB—a question we shall address momentarily. Again, even if you grant that the GCB is possible, you might point out that this new line of reasoning replaces the premise that existence is a per-fection with the weaker premise that necessary existence is a perper-fection.
Though weaker, it might still be doubted along lines similar to those that raised our doubts about the stronger premise. Nonetheless, I hope you’ll agree that the project of formulating a persuasive ontological argument is a tantalizing one.