The ontological argument in brief

In this post, I’m going to try to do something I’ve never done before: attempt write a statement on the ontological argument for inclusion in the book, and make it concise. Here it goes:

The ontological argument is the epitome of an argument that essentially no one actually uses as argument for existence of God, but is instead used to show how sophisticated religious thought supposedly is. These days, it’s even hard to find a philosopher who thinks the argument is good for anything except tormenting philosophy students.

Yet some people think it’s terribly important that atheists deal with the argument properly. Scott Aikin and Robert Talisse (two philosophers at Vanderbilt), go so far as call the ontological argument “the litmus test for intellectual seriousness.” They don’t say why this is, as opposed to the cosmological or design argument being the litmus test of intellectual seriousness. Because of this, I’m going to comment on the ontological argument, but I’m going to keep it very brief.

What is the ontological argument? In reality, there’s more than one ontological argument, but the original one given by St. Anselm (1033-1109) was based on claiming that it’s better to exist in reality than only in the understanding, and therefore it would be contradictory God (defined as the greatest being than can be conceived) to exist only in the understanding. Therefore God exists!

That was just a brief summary, and of course philosophers disagree about how exactly to interpret Anselm’s argument. For our purposes, I just want to mention one of the most famous objections to the ontological argument, made by Anselm’s fellow monk Gaunilo: if the argument works, it would seem to also prove the existence of the greatest conceivable island.

Now an island isn’t the best example for making this point. You might think there’s a limit to how good a god can be, but no limit to how good an island could be. Or you might wonder if the perfect island might exist after all (in heaven, perhaps?) But if you have to, replace “perfect island” with “perfect demon”: analogous to God in every way except for being as evil as possible. Any time anyone tries to tell you anything good about the ontological argument, ask if they have a good answer to that question. If not, you’re safe ignoring them.

In The God Delusion (p. 84), Dawkins claims:

I once piqued a gathering of theologians and philosophers by adapting the ontological argument to prove that pigs can fly. They felt the need to resort to Modal Logic to prove that I was wrong.

Now, philosophers may be a bit annoyed with this story, as it implies that modal logic is just obviously ridiculous. However, while modal logic may or may not be ridiculous, the modal ontological argument is even more vulnerable to parody than Anselm’s argument. For example:

  1. It’s possible that it’s a necessary truth that pigs can fly.
  2. If it’s possible that something is a necessary truth, it’s a necessary truth.
  3. Therefore it’s a necessary truth that pigs can fly.
  4. If something’s a necessary truth, then it’s true.
  5. Therefore, pigs can fly.

I won’t attempt to give a lesson modal logic here, but if you’ve studied it (or are inspired to go study it by reading this), you’ll realize that this argument that pigs can fly is just as logically valid as the modal ontological argument.

I should note that Alvin Plantinga, the most famous proponent of the modal ontological argument, doesn’t claim it proves the existence of God. Instead, he claims it shows that it’s reasonable to believe in God. I think this claim is wrong, but rather than explain why, I’ll just say that I think Graham Oppy gets this issue exactly right in his Stanford Encyclopedia of Philosophy article on ontological arguments, and you should read that if you care about the issue.

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