5. The Ontological Argument from the Possibility of God’s Existence to His Actuality

The last argument I wish to discuss is the famous ontological argument, originally discovered by St. Anselm. This argument has been reformulated and defended by Alvin Plantinga, Robert Maydole, Brian Leftow, and others.⁴⁵ I’ll present the version of the argument as stated by Plantinga, one of its most respected contemporary proponents.

Plantinga’s version is formulated in terms of possible worlds semantics. For those who are unfamiliar with the semantics of possible worlds, let me explain that by “a possible world” I do not mean a planet or even a universe, but rather a complete description of reality, or a way reality might be. Perhaps the best way to think of a possible world is as a huge conjunction p & q & r & s . . . , whose individual conjuncts are the propositions p, q, r, s, . . . . A possible world is a conjunction that comprises every proposition or its contradictory, so that it yields a complete description of reality—nothing is left out of such a description. By negating different conjuncts in a complete description we arrive at different possible worlds:

W₁: p & q & r & s . . .
W₂: p & not-q & r & not-s . . .
W₃: not-p & not-q & r & s . . .
W₄: p & q & not-r & s . . .
Etc.

Only one of these descriptions will be composed entirely of true propositions and so will be the way reality actually is, that is to say, the actual world.

Since we’re talking about possible worlds, the various conjuncts that a possible world comprises must be capable of being true both individually and together. For example, the proposition “The Prime Minister is a prime number” is not even possibly true, for numbers are abstract objects that could not conceivably be identical with a concrete object like the Prime Minister. Therefore, no possible world will have that proposition as one of its conjuncts; rather its negation will be a conjunct of every possible world. Such a proposition is necessarily false, that is to say, it is false in every possible world. By contrast, the proposition “George McGovern is the President of the United States” is false in the actual world but could be true and so is a conjunct of some possible worlds. To say that George McGovern is the President of the United States in some possible world is to say that there is a possible complete description of reality having the relevant proposition as one of its conjuncts. Similarly, to say that God exists in some possible world is to say that the proposition “God exists” is true in some complete description of reality.

Now in his version of the argument, Plantinga conceives of God as a being that is “maximally excellent” in every possible world. Plantinga takes maximal excellence to include such properties as omniscience, omnipotence, and moral perfection. A being that has maximal excellence in every possible world would have what Plantinga calls “maximal greatness.” Now Plantinga argues,

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 it exists in every possible world.
4. If a maximally great being exists in every possible world, then it exists in the actual world.
5. If a maximally great being exists in the actual world, then a maximally great being exists.
6. Therefore, a maximally great being exists.

5.1. Premise 1

It might surprise you to learn that steps (2)–(6) of this argument are relatively uncontroversial. Most philosophers would agree that if God’s existence is even possible, then he must exist. The principal issue to be settled with respect to Plantinga’s ontological argument is what warrant exists for thinking the key premise “It is possible that a maximally great being exists” to be true.

The idea of a maximally great being is intuitively a coherent idea, and so it seems plausible that such a being could exist. In order for the ontological argument to fail, the concept of a maximally great being must be incoherent, like the concept of a married bachelor. The concept of a married bachelor is not a strictly self-contradictory concept (as is the concept of a married unmarried man), and yet it is obvious, once one understands the meaning of the words “married” and “bachelor,” that nothing corresponding to that concept can exist. By contrast, the concept of a maximally great being doesn’t seem even remotely incoherent. This provides some prima facie warrant for thinking that it is possible that a maximally great being exists.

5.2. Dawkins’s Response

Dawkins devotes six full pages, brimming with ridicule and invective, to the ontological argument, without raising any serious objection to Plantinga’s argument. He notes in passing Immanuel Kant’s objection that existence is not a perfection; but since Plantinga’s argument doesn’t presuppose that it is, we can leave that irrelevance aside. He reiterates a parody of the argument designed to show that God does not exist because a God “who created everything while not existing” is greater than one who exists and creates everything.⁴⁶ Ironically, this parody, far from undermining the ontological argument, actually reinforces it. For a being who creates everything while not existing is a logical incoherence and is therefore impossible: there is no possible world that includes a non-existent being that creates the world. If the atheist is to maintain—as he must—that God’s existence is impossible, the concept of God would have to be similarly incoherent. But it’s not. That supports the plausibility of premise (1).

Dawkins also chortles, “I’ve forgotten the details, but I once piqued a gathering of theologians and philosophers by adapting the ontological argument to prove that pigs can fly. They felt the need to resort to Modal Logic to prove that I was wrong.”⁴⁷ This is just embarrassing. The ontological argument just is an exercise in modal logic—the logic of the possible and the necessary. I can just imagine Dawkins making a spectacle of himself at this professional conference with his spurious parody, just as he similarly embarrassed himself at the Templeton Foundation conference in Cambridge with his flyweight objection to the teleological argument!

6. Conclusion

We’ve examined five traditional arguments for the existence of God in light of modern philosophy, science, and mathematics:

1. the cosmological argument from contingency
2. the kalam cosmological argument based on the beginning of the universe
3. the moral argument based upon objective moral values and duties
4. the teleological argument from fine-tuning
5. the ontological argument from the possibility of God’s existence to his actuality

These are, I believe, good arguments for God’s existence. That is to say, they are logically valid; their premises are true; and their premises are more plausible in light of the evidence than their negations. Therefore, insofar as we are rational people, we should embrace their conclusions. Much more remains to be said and has been said.⁴⁸ I refer you to the works cited in the footnotes and bibliography, should you wish to explore further. But I trust that enough has been said here to show that the traditional theistic arguments remain unscathed by the objections raised by the likes of New Atheists such as Richard Dawkins.