Proving the existence of God: the Ontological Argument

There is one argument for the existence of God that is revered and loved by atheists and theists alike: the Ontological Argument for God’s existence. This is not to say that it is loved and revered by all. This argument has certainly had its enemies along the way. However, many, even those who don’t believe the conclusion, think it’s an exceedingly interesting argument. Ironically, it is also, by far, the least used argument in Christian apologetics. In this post, I try to show why it’s so terrific while attempting to make it (somewhat) more accessible.

The Greatest Conceivable Being

The ontological argument is an old argument. It was first developed by Anselm of Canterbury in the 11^th Century.

One thing I love about Anselm is that he couches the discussion in a devotional exercise. In reflecting on and praying to God, Anselm comes to see that his concept of God is a being “that than which nothing greater can be conceived.” What he means by this is that God is perfect in every way, in every aspect. As a matter of concept, God, in all of his properties, is the greatest in every conceivable way.

Now I think that this already is an extraordinary accomplishment. What Anselm has done is clarified a proper understanding of the term God. In other words, one could call Zeus a god. But Zeus is clearly not the greatest conceivable being. Though he was very powerful, he had limits of all sorts, both in power and in moral shortcomings. Or an ancient Egyptian can think of the Pharaoh as a god. But clearly he is not God in this rich sense. I mean he’s really just some dude with a fancy headdress. When we reflect on this, we see that these limited gods are really more like super-humans than they are gods.

Anselm clarifies that something limited is quite simply not what he and many others mean by the term “God.” Anselm (and I) is not really all that interested in something finite or a God with limits. The God of interest (and our devotion) is the God who could not possibly be greater.

I actually think this is the very conception a typical (informed) Christian has in mind when the Christian affirms God’s existence. It also therefore informs Bible study, as well as theology and apologetics. For example, when an unbeliever argues that for God to wipe out whole people groups at a few points in the Old Testament as a problem, the Christian doesn’t simply concede. By contrast, if one claimed that Zeus does evil things, from time to time, a follower of Zeus would presumably simply agree and say that’s why one should make sacrifice to Zues. However, the Christian will argue that God is good even in light of these passages of extreme judgment and bloodshed (see Paul Copans excellent book for a defense of this).

Or, for an example from theology, many Christians reject open theism (the idea that, given human freedom, God does not know the future) precisely because it seems to make God limited. God doesn’t know (i.e., has a limited view of) what free creatures will do in the future. But how can God have this sort of limit, this sort of lack?[1]

The Argument

Okay, with this conception of God in hand, Anselm considers what he takes to be some logical implications. One sort of rough and ready way to interpret what Anselm claims in this argument is that God as the greatest conceivable being (the GCB for short) must have all great-making properties. That is, the GCB must be greatest in every respect. If there is a property that makes a being great, then the GCB must have it. So, for example, if it is greater to be all powerful than being limited in power, then the GGCB must be all powerful. If it is greater to be all knowing rather than limited in knowledge, then the GCB must be all knowing.

Now ask yourself this question: is it greater to exist or not exist? Is it greater to be a figment of one’s imagination or actually existing in reality? Anselm seemed to think that existence itself is a great-making property. If that’s right, then God as the GCB must have the property of existence because if he didn’t there would be something greater than the greatest conceivable being and this is a contradiction. Thus, we’ve got ourselves an argument for the existence of God on the basis of understanding him as the GCB. Here is Anselm:

Even a fool, when he hears of … a being than which nothing greater can be conceived … understands what he hears, and what he understands is in his understanding.… And assuredly that, than which nothing greater can be conceived, cannot exist in the understanding alone. For suppose it exists in the understanding alone: then it can be conceived to exist in reality; which is greater.… Therefore, if that, than which nothing greater can be conceived, exists in the understanding alone, the very being, than which nothing greater can be conceived, is one, than which a greater can be conceived. But obviously this is impossible. Hence, there is no doubt that there exists a being, than which nothing greater can be conceived, and it exists both in the understanding and in reality (Proslogium as quoted here) .

Let’s try to formalize this:

1. Everyone can understand God as the greatest conceivable being
2. If God exists as only a figment of the imagination, then I can conceive of something greater than the greatest conceivable being, namely, things that exist in reality.
3. But it is a contradiction to think I can conceive of something greater than the greatest conceivable being.
4. Therefore, God cannot be simply a figment of the imagination.
5. Therefore, God exists in reality.

Here’s another formulation that’s a bit simpler:

6. God is the greatest conceivable being (by definition)
7. The greatest conceivable being must have all great-making properties (by definition)
8. Existence is a great-making property. (premise)
9. Therefore, God has existence.

Gaunilo’s Objection

The immediate push back for Anselm was a Benedictine monk named Gaunilo. He was a contemporary of Anselm. Gaunilo argued that if this works for God, it can work for anything so long as we understand it as the greatest conceivable x. But it is absurd to think that we can argue the existence of anything so long as we prefix it with the greatest conceivable x. And therefore, by parody, the argument for God must be flawed as well. He gives an argument for the greatest conceivable Island. If we map it onto the argument above it might go something like:

10. Atlantis (a hypothetical island conceived in our minds) is the greatest conceivable island.
11. The greatest conceivable island must have all great-making properties.
12. Existence is a great-making property.
13. Therefore, Atlantis exists.

Now the problem with this argument is that premise 5 looks to be logically incoherent. More specifically, the notion of a greatest conceivable island seems to be incoherent. Plantinga has said:

…it’s impossible that there be such an island. The idea of an island than which it’s not possible that there be a greater is like the idea of a natural number than which it’s not possible that there be a greater, or the idea of a line than which none more crooked is possible. And the same goes for islands. No matter how great an island is, no matter how many Nubian maidens and dancing girls adorn it, there could always be a greater—one with twice as many, for example. The qualities that make for greatness in islands—number of palm trees, amount and quality of coconuts, for example—most of these qualities have no intrinsic maximum…So the idea of a greatest possible island is an inconsistent or incoherent idea; it’s not possible that there be such a thing.[2]

But what about the notion of a greatest conceivable being? Here it looks as if, unlike an island, a being can be genuinely the greatest—especially in the sense of being maximal. So a being can be maximal in knowledge. That is, the being can know all truths. A being can be maximally powerful. That is, the being can have the power to realize all logical possibilities. A being can be maximally good where all of the being’s actions are morally righteous.

So when it comes to things like islands, there is no maximal properties that constitute great making properties. But not so, when it comes to beings whose properties can be had maximally.

Kant’s Objection

The second historical and much more persuasive (at least for many) objection that is often brought up in connection with Anselm’s argument comes from Immanuel Kant. Kant says:

“Being” is obviously not a real predicate; that is, it is not a concept of something which could be added to the concept of a thing…Logically, it is merely the copula of a judgment. The proposition “God is omnipotent” contains two concepts, each of which has its object—God and omnipotence. The small word “is” adds no new predicate, but only serves to posit the predicate in its relation to the subject. If, now, we take the subject (God) with all its predicates (among which is omnipotence), and say “God is,” or “There is a God,” we attach no new predicate to the concept of God, but only posit it as an object that stand in relation to my concept (Critique of Pure Reason).

Kant’s push back then is that existence is not a predicate or a property. Why? Kant thinks that saying that something exists doesn’t further fill out a concept of something (i.e., doesn’t provide a genuine property of that thing). Imagine conceptually what it is to be a unicorn. If I know my unicorns, it is for a thing to be a horse with a single horn (and perhaps rainbow colored and whatever else). Though I believe that unicorns do not exist, it doesn’t seem the concept includes nonexistence as a property. If you were to be in the woods and a unicorn ran by you, you wouldn’t think that you now have to change the concept you previously had in mind. There’s the concept of a unicorn, on one hand, and then the question of existence, on the other. Or let’s say squirrels suddenly went extinct (i.e., squirrels no longer exist). You wouldn’t think that the concept of a squirrel has now changed. Rather we would simply believe that there are no instances of the squirrel concept (or something less nerdy).

If existence is not a property, then it can’t be a great-making property. That is, premise 7 of Anselm’s argument is false.

The Modal Version

Now this does seem to be a problem for the way the argument is stated above.[3] But contemporary defenders of the argument have given a fuller expression to thinking of God as maximal. That is, so far all we have talked about is God’s being maximal in properties. But there is, in a way, a richer sense of God as the greatest conceivable being. This is where we turn to a modal version of the argument (i.e., one that talks in terms of possibility and necessity). The crucial piece, it seems, of the modal version is to say that maximal greatness would be to exist as maximally great in all possible worlds. That is truly the greatest conceivable being. If this notion of a maximally great being that exists in all possible worlds is possible, then it follows that the maximally great being exists in the actual world (if that just blew your circuits, take the formal version slowly).

Here is one formalized version of the modal argument:

1. A being is maximally great in any possible world only if it is maximally great in every possible world.
2. It is possible that a maximally great being exists.
3. If it is possible that a maximally great being exists, then a maximally great being exists in some possible world.
4. If a maximally great being exists in some possible world, then it exists in every possible world. (Given 1, 2 and 3)
5. If it is possible that a maximally great being exists in every possible world, then it exists in the actual world.
6. Therefore, a maximally great being exists in the actual world.

Notice that this is formulated without making existence a property. So Kant’s objection is, in a way, sidestepped.

The most controversial premise here (at least in my mind) is premise 1. But when I ask myself what it would mean for a being to be perfectly maximal, then I find it very plausible that this being must be maximal in all possible worlds, not just some possible world or the actual world.

There’s of course a lot more that needs to be said but, at minimum, this makes an interesting case for the existence of the maximally great being.

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[1] Open theists have of course answered this sort of objection and the discussion is far more sophisticated than what I’m presenting here. However, I’m suggesting that OT has, for many, this intuitive drawback.

[2] Alvin Plantinga (God, Freedom and Evil), 90-91.

[3] Plantinga doesn’t think it is a problem for the way he formulates Anselm’s argument. This is because Plantinga does not construe it in terms of great-making properties.