10 Apologetic Arguments - The Ontological Argument

The ontological argument is a traditional Christian argument, but it is probably the least understood and least practical of all them all, the ultimate acquired taste. It requires a keen philosophical sense to grasp. I’ll lean heavily here on others to explain this argument, because of its complexity. I believe it is an argument that a person should ponder, but I don’t expect it to sweep most people off their feet.

From Anselm, Descartes, and Kant

Anselm’s approach (11th century) to this argument is beautiful. He writes his argument, not as an appeal to man, but as a prayer to God:

And so, Lord, do you, who gives understanding to faith, give me, so far as you know it to be profitable, to understand that you are as we believe and that you are that which we believe. And indeed, we believe that you are a being than which nothing greater can be conceived. … Even the fool is convinced that something exists in the understanding, at least, than which nothing greater can be conceived. For, when he hears of this, he understands it. And whatever is understood, exists in the 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.1

Got it? Rene Descartes (17th century) explains,

Certainly, the idea of God, or a supremely perfect being, is one which I find within me just as surely as the idea of any shape or number. … God can be thought of as not existing. But when I concentrate more carefully, it is quite evident that existence can no more be separated from the essence of God than … the idea of a mountain can be separated from the idea of a valley. Hence it is just as much of a contradiction to think of God (that is, a supremely perfect being) lacking existence (that is, lacking a perfection), as it is to think of a mountain without a valley.2

The basic idea seems to be that the existence of the idea of a maximally great being such as God has its own implications. If the being that you have conceived of does not actually exist, then he is not a maximally great being, as existence is a better quality to have than nonexistence. Thus, for the maximally great being to exist as an idea, he must also exist in reality.

Immanuel Kant is credited with undermining the classic ontological argument. He does so on two grounds. First, he claims that it is not exactly fair to speculate about the existence of a being or fact that by definition cannot be denied. Second, Kant claims, “‘Being’ is obviously not a real predicate.”3 In other words, you cannot ascribe to a thing “existence” as a quality in the same way that you would ascribe to it “omnipotence” or appearing “red.” For Kant, a thing can be red, but a thing cannot be “being.”

Plantinga’s Revision

However, this medieval argument has been rescued of late by none other than Alvin Plantinga. He has restated the argument in terminology that has revitalized the debate over this approach. It goes something like this:4

It is possible that God exists. By possible, we simply mean that it is conceivable. It is an idea that can be had that is not contradictory to itself. In contrast, a married bachelor cannot exist either in idea or reality.

If it is possible that God exists, then God exists in some possible worlds. Here, possible worlds mean hypothetical scenarios. The only way that something can be possible (the truth affirmed by premise 1) is if there is a hypothetical scenario where the fact is true. If there is no hypothetical scenario where a thing exists, then the thing cannot possibly exist, as with the married bachelor.

If God exists in some possible worlds, then God exists in all possible worlds. By definition, God is what is called “necessary” (kind of like a definition). If God is the something-than-which-nothing-greater-can-be-thought, then there can be no definition of God that makes him “contingent,” something that either could or could not exist. If God is not necessary, then he is not a maximally great being, as being necessary is greater than being contingent.

If God exists in all possible worlds, then God exists in the actual world. This follows because the actual world must be one of the hypothetical, possible worlds. Stated negatively, the actual world cannot be an impossible world. If God exists in every possible world, then he must exist in this one, the one that is real.

If God exists in the actual world, then God exists. Defenders of this argument see it as a decisive logical and even mathematical proof of God’s existence. Skeptics see it as a word game. I personally believe the conclusion is valid, but I also doubt very many skeptics will ever be persuaded by it because it is so very complicated.

Here's a helpful video on Plantinga's version of the argument.

Ben Williams is the Preaching Minister at the Glenpool Church of Christ and a regular writer at So We Speak. Check out his new book Why We Stayed or follow him on Twitter, @Benpreachin.