The Ontological Argument

There are a variety of ontological arguments, and while none of them are any good, I’ll talk about one version that William Lane Craig (among many others) have talked about. William Lane Craig describes this curious fact of the ontological argument: if God’s existence is even possible, then it follows that God exists. In some cases he mentions it in a debate without providing much further context, which I think delivers a false impression upon many who hear it.

At reasonable faith, William Lane Craig describes the argument thusly, borrowing largely from Christian philosopher Alvin Plantinga:

1. It is possible that a maximally great being (God) exists.
2. If it is possible that a maximally great being exists, then a maximally great being exists in some possible world.
3. If a maximally great being exists in some possible world, then it exists in every possible world.
4. If a maximally great being exists in every possible world, then it exists in the actual world.
5. Therefore, a maximally great being exists in the actual world.
6. Therefore, a maximally great being exists.
7. Therefore, God exists.

For those unfamiliar with the argument, let me explain. A maximally excellent being entails being omnipotent, omniscient, and perfectly good. A maximally great being is one that has maximal excellence in every possible world (where a possible world is a complete description of the way reality is or could have been like). Thus, a maximally great being by definition exists in all possible worlds, if such a being exists at all.

Here’s how it works. As an analogy, suppose you know that all the balls are in the bucket, making the bucket full, or none of the balls are in the bucket. You get a peek at the bucket and see that there is at least one ball in the bucket. In that case, you rightly deduce that all the balls are in the bucket. Similarly, God is defined as a necessary being, which means he exists in all possible worlds if he exists at all. Thus God exists either in all possible worlds (if he exists) or none of them (if he does not exist). If God is possible (as premise 1 claims), then he exists in at least one possible world, but if he exists in at least one possible world, then he exists in all of them.

The main problem with this argument is that it cuts both ways. If God’s nonexistence is possible, then we know “God does not exist” is true in at least one possible world. But since God exists in all possible worlds or none of them, it follows that if God does not exist in a possible world, then he exists in none of them. It would be like getting a peek at the bucket and finding that at least one of the balls isn’t in there (as by seeing that the bucket is at least half empty). Thus “It is possible for God to not exist” entails “God does not exist.” That is, if we switch premise 1 with “It is possible that a maximally great being (God) does not exist” we wind up with the opposite conclusion! As such, the ontological argument is hardly a convincing one for a person who isn’t already a theist.