Alvin Plantinga’s ontological argument, does the multiverse prove God?

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Does the multiverse prove that God exists?

April 24, 2023 -

Professor teaching at class, pointing to a white board © By Sidekick/

Professor teaching at class, pointing to a white board

Professor teaching at class, pointing to a white board © By Sidekick/

Countless new blockbuster movies tout the “multiverse” theory, an idea that allows the characters to travel to other parallel realities. The original scientific theory was given by Dr. Hugh Everett in 1957 as an interpretation of quantum physics (don’t worry, we won’t go there). As I’ve written about elsewhere, some scientists believe infinite parallel universes exist.

Humans couldn’t physically access these other universes, so we can’t test the theory with experiments. Some scientists believe in the multiverse theory to avoid the “anthropic principle,” which asks, “Why is the universe so perfectly fine-tuned for humans?” Christians have an answer readily available: God created the universe. That argument for God is called the design argument, and it’s a good argument.

I want to discuss another, more controversial proposition: the ontological argument.

It comes from a medieval philosopher named St. Anselm of Canterbury (1033–1109) and was lately resurrected by several philosophers, including modern Christian philosopher Alvin Plantinga. (I talk more about him in “Does evolution prove God? Alvin Plantinga’s Christian philosophy).”

Let’s get into the argument.

What is the “possible worlds” theory?

Philosophers have an idea like the multiverse: “possible worlds.” Instead of believing the other worlds actually exist, we use possible worlds as a thought experiment.

Let’s run one now. In the real world, humans traveled to the moon in 1969. Let’s imagine a scenario where some of the top scientists in the US were never born and the US had to fake the moon landing to compete with Russia. That situation seems possible because we could imagine a world where it would have happened, even though it didn’t in our reality.

So, in one possible world, the US faked the moon landing.

Now, try to imagine another world where 2 + 2 = 5; for that reason, NASA could never get a spaceship on the moon. We can’t imagine that because it’s impossible. Therefore, of all the worlds that could possibly exist, none exist where 2 + 2 = 5. In every possible world, including our world, 2 + 2 = 4.

What does the possible world thought experiment show?

Some things are necessarily true, but some things might or might not have been true.

In one possible world, unicorns exist, even though in our world, they don’t. However, in no universe does a triangle have four sides; a world where that’s true is impossible.

We can boil it down even further: Some things are possible, some things are impossible, and for some things, it’s impossible for it not to be true (like 2 + 2 = 4). These kinds of things are necessarily true—remember that phrase.

This is an introduction to what’s called “modal logic,” the study of the logic “of the expressions ‘it is necessary that’’ and ‘’it is possible that.’”

Congratulations! You made it this far.

Now, we’ll look at Plantinga’s version of the ontological argument for God.

Plantinga’s “victorious” ontological argument

We can think of God as a maximally great being—the best being possible. This means God is omniscient (all-knowing), omnipresent (not constrained to any one place), omnipotent (all-powerful), and perfectly good.

Do you think it’s possible for a “maximally great being” to exist? Put another way, could you imagine a world in which God exists? Yes?

OK, now let’s examine that possible world.

In that reality, God would necessarily exist; in that possible world, he must exist. Why? Because he’s maximally great—he created everything and acts as the foundation for the world’s existence. In that possible world, he wouldn’t be dependent on anything else. In other words, being necessary would be a part of his greatness.

In that possible world where he exists, he would necessarily exist.

Here’s where the “modal logic” comes into play. If God is necessary in one possible world, he must exist in all possible worlds—including the actual world, our world. Remember 2+2=4, that truth is necessary in our world and must be true in all possible worlds.

So the “victorious” ontological argument goes: if God exists in a possible world, he will exist in every possible world, including the real one. Or, God possibly exists. Therefore, he must exist.

The logic in Plantinga’s technical wording of the argument makes it airtight.

What are the responses to the ontological argument?

For this argument to make sense to someone, the idea of God must first make sense to them. The argument doesn’t get off the ground if the notion of a maximally great being doesn’t track in their minds.

Of course, we can take other arguments for God’s existence as evidence for God’s possibility. If we do that, we make the argument less than a slam-dunk “proof” of God’s existence and turn it into another argument. Plantinga agrees with the limitation, but his line of reasoning is still persuasive.

We’ve shown something quite substantial: If someone agrees God could exist, they must admit he does exist. If the idea of a maximally great being seems consistent to us, we should accept that God necessarily exists in all possible worlds, including our own.

So, where do atheists and agnostics disagree?

They might say that necessarily existing doesn’t make a maximally great being any greater. Most don’t appear to go that route, but it’s worth mentioning. Others might deny the idea of “modal logic” from the get-go, but few do.

How else? Well, if we restate the argument in its simplest form, “God possibly exists; therefore he must exist,” it becomes obvious: Deniers of the argument argue God cannot possibly exist. If the idea of God is inconsistent or suspect, he does not necessarily exist.

What about a maximally great pizza?

However, many more pseudo-philosophers deny the ontological argument with a wry, dismissive scoff: “My believing in an all-perfect pizza doesn’t make it exist! How can it be so for God?” From the argument’s beginnings in St. Anselm’s Proslogion, a fellow priest named Guanilo responded with a similar argument (using an island as an example instead of pizza).

The main response to this objection is quite simple: The idea of a maximally great pizza, or island, is incoherent. It’s a bit like an infinitely small pizza, an eternally repeating island, or the babbling of a toddler—incoherent. What makes a maximally great pizza?

Certainly not pineapples, but some might disagree.

See, there’s no objective way to consider the “greatest” pizza.

Arguably, we can objectively consider greatness in the idea of God, unlike pizza or an island.

Is the argument convincing?

Many laypeople hear the argument and believe a semantic sleight of hand has tricked them; alas, that’s one of the argument’s weaknesses. Nevertheless, the argument could compel a few kinds of people, such as a particularly logical individual who has deconstructed their faith and now lives as an agnostic, not an atheist. They might see the logic of the argument, realize they can’t flat-out deny God’s existence, conclude he must be possible, and then come out the other end realizing God must exist.

For many, the ontological argument best serves to strengthen one’s faith. Throughout the centuries, the argument acts primarily to strengthen the resolve of doubting believers. If they think God likely exists, they can be assured he certainly exists.

Dr. William Lane Craig and Dr. J. P. Moreland, two preeminent philosophers and Christian apologists, call this argument a link in the “chainmail” of reasons for belief in God.

The wonders of creation witness to us that God is our all-powerful creator. The ontological argument reflects God’s pure greatness—a commendable, excellent, and praiseworthy thing to meditate on (Philippians 4:8).

Pray with St. Anselm, “Teach me to seek thee, and reveal thyself to me . . . Let me seek thee in longing, let me long for thee in seeking; let me find thee in love and love thee in finding.”

If you seek God, you will find him in every world imaginable.

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