What is the ontological argument?

Question 60102.

The ontological argument is the most demanding of the classical arguments for God’s existence and easily the most disputed. Unlike the cosmological or teleological arguments, which move from features of the world to a conclusion about God, this one attempts to establish God’s existence from the concept of God alone, without any appeal to observation.

That sounds like a conjuring trick, and a good many people have said so. It has also been defended by some of the sharpest minds in the history of philosophy across nearly a thousand years, which suggests there is more to it than sleight of hand. Let me set it out and then give my own assessment.

Anselm’s Original Ontological Argument

Anselm of Canterbury set out the ontological argument in his Proslogion around 1078, in the spirit of Psalm 90:2, and it is worth noting that he wrote it as a prayer rather than a debating brief. He defines God as that than which nothing greater can be conceived, a formulation of some subtlety, since it does not require you to grasp God but only to grasp that nothing greater could be thought.

The argument then proceeds. Even the fool who says in his heart there is no God understands this definition, so the concept exists in his understanding. But existing in reality is greater than existing in the understanding alone. So if that than which nothing greater can be conceived existed only in the understanding, we could conceive of something greater, namely the same being existing in reality.

That would be a contradiction, since we would then have conceived of something greater than that than which nothing greater can be conceived. Therefore, Anselm concludes, that being must exist in reality as well as in the understanding.

Gaunilo’s Perfect Island

The first objection came almost immediately, from a monk named Gaunilo, and it is still the one most people reach for. Imagine, he said, the most perfect island conceivable. By Anselm’s reasoning, since existing is greater than not existing, this island must exist. Since it obviously does not, something has gone wrong with the argument.

Anselm’s reply was that the parody fails because an island has no intrinsic maximum. There is no such thing as the greatest possible number of palm trees; you can always add one. Greatness for an island is a matter of degree with no upper limit, so the concept of a maximally great island is incoherent.

The attributes traditionally ascribed to God are different in kind. Maximal knowledge, maximal power and maximal goodness do have upper bounds: knowing everything true, being able to do everything possible, being wholly good. Whether that reply succeeds is still argued, but it is not the evasion it is sometimes taken for.

Kant’s Objection

The most serious blow came from Immanuel Kant, who argued that existence is not a predicate. When I list the properties of a hundred thalers, adding that they exist tells you nothing further about them; it tells you that something answering to the description is instantiated in the world.

On Kant’s account the ontological argument confuses a statement about a concept with a statement about reality. Defining a being as existing does not make it exist any more than defining a unicorn as horned makes unicorns real. For a long stretch of philosophical history that was taken as the end of the matter.

It is a strong objection and I think it disposes of Anselm’s version as he stated it. What it does not dispose of is the modern reformulation, which does not treat existence as a property in the way Kant assumed.

The Modal Revival

In the twentieth century Charles Hartshorne, Norman Malcolm and later Alvin Plantinga restated the ontological argument using the logic of possibility and necessity, and it has proved considerably more resilient in that form.

The reasoning runs like this. It is possible that a maximally great being exists. If it is possible, then such a being exists in some possible world. But a maximally great being would possess necessary existence, and a being that exists necessarily in one possible world exists in every possible world. Our world is a possible world. Therefore a maximally great being exists.

The logic here is valid, and that is not in dispute. Everything rests on the first premise. If it is genuinely possible that a maximally great being exists, the conclusion follows. And the person who wishes to deny the conclusion must claim that such a being is not only absent but impossible, which is a much stronger claim than most atheists want to defend.

Why the Argument Feels Like a Trick

Even people who cannot fault the logic usually feel that something illegitimate has happened, and I share the discomfort. The sensation is that you cannot get a universe out of a definition, and no amount of formal validity quite removes it.

Part of the difficulty is that possibility in the technical sense is doing heavy work. Saying that a maximally great being is possible sounds modest, but in modal logic it amounts to saying that such a being exists in at least one possible world, and given necessary existence that is very nearly the conclusion already.

So the argument may be valid without being persuasive, because anyone who doubts the conclusion will doubt the premise for the same reasons. That is not a fatal criticism; a great many philosophical arguments are in that position. It does mean the ontological argument is unlikely to move anyone who was not already halfway there.

What It Is Actually Good For

Here is where I think the argument earns its keep, and it is not in evangelism. Its value is conceptual. It clarifies what we mean by God, and it rules out a whole class of confused ideas. The God of Christian theism is not a very large and impressive being among other beings; He is the greatest conceivable being, existing necessarily rather than contingently.

That distinction matters when people ask who made God, or picture the Almighty as an old man somewhere in the sky. A necessary being is not the sort of thing that has an origin, and the ontological argument makes that clear in a way ordinary description often does not.

It also connects with what God says of Himself. When Moses asks for a name in Exodus 3:14 the answer is I AM WHO I AM, which is as close as language gets to the assertion of self-existent being. Anselm was not inventing a concept; he was trying to think clearly about one Scripture had already given him.

Faith Seeking Understanding

Anselm’s own motto, fides quaerens intellectum, describes what he was doing better than any label we could attach. He was not attempting to argue himself into belief. He was a believer trying to understand what he already held, and the Proslogion ends in praise rather than in a conclusion.

That is the right order, and it applies to all the arguments. The cosmological, teleological and ontological arguments are best understood as a Christian thinking hard about what he believes and finding that it holds together, not as a ladder by which an unbeliever climbs to God.

Scripture nowhere argues for God’s existence. It opens with in the beginning God, and it says in Psalm 14:1 that the fool says in his heart there is no God, which is the very sentence Anselm took as his starting point. See the cosmological argument, the teleological argument and the moral argument.

My Own Verdict

I find the ontological argument fascinating and I would not lead with it. In a conversation over coffee it will sound like a word game, and the person you are talking to will suspect they have been manoeuvred rather than persuaded. That suspicion does more damage than the argument does good.

Where it does help is with Christians who have absorbed the idea that faith is intellectually shabby. Discovering that Anselm, Descartes, Leibniz, Gödel and Plantinga have all worked seriously on this is a useful corrective to the notion that thinking people gave up on God some time in the nineteenth century.

And there is something fitting about an argument that ends where it does. If God exists at all, He does not exist the way tables and galaxies exist, dependent and contingent. He exists necessarily, and everything else exists because He does. That is worth taking a long time over.

Descartes and the Later History

The ontological argument did not stop with Anselm. Rene Descartes restated it in the fifth of his Meditations, arguing that existence belongs to the idea of a supremely perfect being as necessarily as the equality of its angles to two right angles belongs to the idea of a triangle.

Leibniz noticed a gap in Descartes and tried to close it, arguing that one must first show the concept of a supremely perfect being to be coherent, since an argument from an incoherent concept proves nothing. He believed he had done so, and the point remains a live one in the modern debate.

In the twentieth century Kurt Godel, one of the greatest logicians who ever lived, left behind a formal version of the argument in modal logic which has been checked by automated theorem provers and found valid. Whether the premises are true is another matter, but nobody can any longer dismiss the ontological argument as obviously fallacious.

So, now what?

If philosophy is your thing, read the Proslogion; it is short and it is beautiful, and it will take an evening. If it is not your thing, take from the ontological argument the one point that matters pastorally: the God of the Bible is not a big thing in the universe but the reason there is a universe at all.

Then let that reshape how you pray. Most of our prayers are addressed, if we are honest, to a slightly enlarged version of ourselves. Anselm was reaching for a God greater than anything he could think, and he ended up on his knees. Where do your prayers end up?

God said to Moses, I AM WHO I AM. And he said, Say this to the people of Israel: I AM has sent me to you.

Exodus 3:14 (ESV)