The Ontological Argument for the Existence of God

The ontological argument has always been one of my favorites. While it’s a little esoteric, it’s truly one of the most fascinating attempts to prove the existence of God.

It dates all the way back to the 11th century, originating with Saint Anselm of Canterbury—an Italian monk, philosopher, and theologian. In the centuries since its conception, it has garnered the attention of some of history’s greatest minds, enduring many critiques and proving itself to be worthy of serious consideration. It takes a little work to wrap your mind around, but I think it’s worth it.

Possible World Semantics

The argument relies on a concept used in modal logic called possible world semantics. It sounds confusing, but it’s pretty straightforward. 

We all spend time thinking about things that could have happened but didn’t. Like what if I studied more for that test? What would my life be like if I chose a different job? What would the world look like if the US never dropped a bomb on Japan? Decisions both big and small create an unavoidable ripple effect that changes the course of history.

Any complete description of how the world would have been, given a different set of circumstances, is a “possible world.” For example, there is a possible world where I didn’t write this article, a possible world where Mitt Romney beat Barrack Obama for president in 2012, and a possible world where baseball was fun to watch (to be honest I’m not entirely sure on this last one). The idea of possible worlds helps to differentiate between the actual world and the near-infinite number of ways things could have been if people chose to act differently. Understanding this is crucial to understanding the argument. 

One more thing before we get there though. You’ll notice the phrase “maximally great being” is used in the argument, which can be a little confusing. But it is simply what we mean by “God.” By definition, God is the greatest conceivable being, or, as Anselm put it, “a being than which no greater can be conceived.” If you could conceive of a being greater than God then that would in fact be God. Note that this says nothing about whether such a being actually exists, it’s just a functional definition of the concept of God.

The Argument

So with all that out of the way, the following is a formal version of the argument derived from the contemporary philosopher Alvin Plantinga.

  1. It is possible that a maximally great being 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 a maximally great being exists in every possible world
  4. If a maximally great being exists in every possible world, then a maximally great being exists in the actual world

I remember being lost the first time I heard this. The first two premises seem fairly straight forward—that if it is even possible that God exists, then He must exist in some possible world. Premise 3 is what really tripped me up. How do you make the jump from a maximally great being existing in some possible worlds to all possible worlds?

This is the crux of the argument and it has to do with what it means to be “maximally great.” Most people agree that a perfect being would have characteristics such as omniscience (all-knowing), omnipotence (all-powerful), and omnibenevolence (all-loving). But in addition to these qualities, wouldn’t a being that existed in every possible world be better than a being that only existed in some possible worlds? In other words, existing in all possible worlds, and not just some possible worlds, is part of what it means to be “maximally great.” Therefore, if a maximally great being exists in some possible worlds, it logically follows that He exists in all possible worlds and thus exists in the actual world.

I know that this will seem like a rather cold and abstract way to prove the existence of God to most people. But the implications of this argument are quite astounding. 

Most philosophers agree that the argument is valid, meaning that if the premises are true, then it is impossible for the conclusion to be false. Premises 2, 3, and 4 are uncontroversially true, so the only way to disprove the argument is to show that premise 1 is false.

But remember that premise 1 just states that it is possible that a maximally great being exists. So in order to avoid the conclusion that God exists, the skeptic would have to show that it is logically impossible for God to exist. They couldn’t merely say that there’s no good evidence to believe in God or that it is extremely unlikely that God exists, they would have to prove that the very concept of God is incoherent—like a square circle or a single married person.

Most atheists would not make such bold claims. Even Richard Dawkins—probably the world’s most famous living atheist—admits that he can’t be certain that God doesn’t exist, he just finds it very improbable. But Richard Dawkins, along with many other atheists like him, don’t recognize the logical implications of their views given the ontological argument—that if it is even possible that God exists, then it follows that He does, in fact, exist.

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