In the year 1078, a monk named Anselm of Canterbury astonished the world by arguing that if it is even possible that God exists then it follows logically that God does exist. Anselm’s argument came to be called the ontological argument, and it has sharply divided philosophers ever since. The 19th century German philosopher Arthur Schopenhauer called it a charming joke, but many prominent twentieth century philosophers such as Charles Hartshorne, Norman Malcolm, and Alvin Plantinga think that it is sound. Here it is. Theologians define God as a maximally great being. If something were greater than God, then that being would be God. In addition, in order to be maximally great, a maximally great being would have to be all-powerful, all knowing, and morally perfect in every possible world. Possible worlds are simply ways the world could have been. To say that something exists in a possible world is just to say that if the world were that way, then the thing would have existed.

For example, even though unicorns do not exist in the actual world, it seems at least possible that they could have, so we can say that unicorns exist in some possible world. On the other hand, a married bachelor does not exist in any possible world because the idea of a married bachelor is logically incoherent. It could not possibly exist. Therefore, if it is possible that a maximally great being exists, then we can say that he exists in some possible world. However, wait; a maximally great being would not really be maximally great if it existed in only some possible worlds. To be maximally great it has to be all-powerful, all knowing, and morally perfect in every possible world. So think about it, if a maximally great being exists in any possible world, then it exists in every possible world, and if it exists in every possible world, then it exists in the actual world. That is, a maximally great being actually exists. Thus, the atheist has to maintain not simply that God does not exist, but that it is impossible that God exists.

Here is a summary of the ontological argument. Steps two through six are straightforward and largely uncontroversial, but what about point number one? Clearly if theologians can show that the idea of a God is logically incoherent, then the argument fails, but is the idea of a maximally great being absurd, like a married bachelor or a square circle or the smell of blue? This does not seem to be the case. The notion of the all-powerful, all-knowing, morally perfect being that exists in every possible world seems to be a perfectly coherent idea. However, could we parody this argument and make it work for anything? Why not say it’s logically possible that a maximally great pizza exists, therefore a maximally Great pizza does exist. However, the idea of a maximally great pizza is not like the idea of a maximally great being. In the first place, there are not intrinsic maximal values that make pizzas great. There could always be one more pepperoni to increase its greatness. It is not even obvious what properties make a pizza great: thin crust or thick crust, extra cheese, anchovies? It is relative to the taste of the consumer. In the

second place, a maximally great pizza would have to exist in every logical possible world, but that would mean people could eat it. Therefore, it would not really be a pizza because a pizza is something you can eat. The idea of a maximally great pizza turns out not to be a coherent idea. The idea of God, on the other hand, is an intuitively coherent idea. Therefore, his existence is a possibility. In addition, the ontological argument shows that if God possibly exists, then God actually exists.

PRIMARY SOURCE: Dr. Craig Videos; Ontological Argument