Imagine your perfect house. Maybe it has a built-in movie theatre or indoor swimming pool. Maybe it’s on a ski slope in the Rocky Mountains or a beach in the Caribbean. Certainly, there’s some optimal combination of location, number of bedrooms, basement features, and kitchen layout that will make you think, “That’s the perfect house.” However, your perfect house is missing one thing – it doesn’t exist. Wouldn’t it be even more perfect if it did?

The Explanation

If your perfect house would be more perfect if it actually existed and you could live in it, then it must exist. After all, if it did not exist, then it would not be your perfect house. Imagine there are two dream houses side-by-side that are identical in every way from the number of windows to the type of roof to the color of the convertible parked outside. There is only one difference between them – Dream House #1 actually exists in real life, and Dream House #2 is only in your head. This one difference, the difference in their existence, makes Dream House #1 better than Dream House #2.

This kind of reasoning motivates what is called the ontological argument – except instead of your perfect house, it serves as an argument for the existence of God, or a perfect being. The ontological argument says that if you can imagine a perfect being, it would be more perfect if it existed; therefore, it must exist.

Definition of the Ontological Argument

The ontological argument claims that God exists because if he did not exist, he would not be the most perfect being, and if he were not the most perfect being, then he would not be God. What makes the ontological argument unique as an argument for God’s existence is that it is entirely a priori, or an argument from reasoning, and requires no empirical evidence about our world.

The History

Saint Anselm of Canterbury first posed the ontological argument in 1078. Anselm’s argument asks us to imagine a being superior to all. Therefore, this being must be all-knowing, all-powerful, and completely good. However, if this being only exists in our mind, we can then imagine another being, as great as the first, that exists in reality. It follows that the first being is, therefore, not a being greater than all since the same being existing in reality would be greater than the one that only exists in our minds. Anselm concludes that this greatest being must exist, and this being is God.

Anselm’s ontological argument has come under criticism since it was first proposed. One of his first and greatest critics was a fellow monk and contemporary named Gaunilo. Gaunilo denied the very basis of Anselm’s reasoning, that it is possible to imagine a being than which nothing is greater. After all, unlike the concept of our perfect house, where it would be possible to define the perfect proportion of rooms to windows, the properties of a perfect being have no bounds. There is no perfect amount of power to have; this being must have an infinite amount of power. Just as we may not have a concept of the largest number, we also may not have a concept of the most perfect being. 

Further, Gaunilo pressed, the ontological argument proves the existence of too much. Like the perfect house example, it can be used to prove the existence of anything, including perfect islands, soulmates, or even worlds. To avoid this problem, a contemporary defender of the ontological argument must explain why it should only apply to God and not to other perfect things.

18th-century German philosopher Immanuel Kant levied another kind of objection against the ontological argument. Notice that when explaining a perfect being, the things that make it perfect are all predicates, or words that reflectively describe the being. For example, I might say, “God is completely good.” “Completely good” describes God. However, Kant argued that existence does not operate as a predicate because it does nothing to explain or describe what God essentially is. Saying God exists in reality or only in our mind does not add to or detract from our concept of a perfect being. Thus, existence cannot be used as a predicate to make a being than which nothing is greater more or less great since existence does not change its concept.

So What?

Arguments for God’s existence are important because throughout history, wars have been fought and friendships broken in the name of religion. God is central to many people’s moral and political values, yet the existence or nonexistence of God is often taken as an assumption rather than needing evidence itself. The ontological argument has been and continues to be one of the most debated and discussed arguments in the history of philosophy. It’s one that theists and atheists alike must confront and respond to if they are to back up their claims with solid reasoning and evidence. Many philosophers have attempted to amend and revise Anselm’s ontological argument in light of historical objections. Specifically, contemporary philosopher Alvin Plantinga offers an ontological argument that uses modal logic and the language of possibility.

If you find the ontological argument convincing, consider what you are committed to when using this reasoning. Does this mean your dream house exists, or does the ontological argument apply to God exclusively? Why?

If you find the ontological argument unconvincing, this does not mean you are committed to atheism. Several other arguments attempt to prove God’s existence, including Thomas Aquinas’ argument for God (the cosmological argument) and the argument from intelligent design (the teleological argument). Both of these use empirical evidence from our world to argue for God. Keep in mind that when someone uses faulty reasoning as evidence for their view, this does not mean their conclusion must be false. The proof may not be compelling, but there may be a sound argument that leads to the same conclusion. You may find that even if you reject the reasoning of the ontological argument, you can be convinced of God’s existence in another way.

    Learn More

    1. Crashcourse. “Anselm & the Argument for God: Crash Course Philosophy #9.” Youtube, 4 April 2016,
    2. Haight, David and Marjorie. “An Ontological Argument for the Devil.” The Monist, vol 54, no. 2, 1970, pp. 218-220.
    3. Oppy, Graham. “Ontological Arguments.” The Stanford Encyclopedia of Philosophy, Spring 2020.
    4. Plantinga, Alvin. The Ontological Argument. MacMillian, 1968.

    Think Further

    1. Do you think that something existing always makes it better or greater? Why?
    2. Can you think of how Anselm might respond to Gaunilo or Kant’s objections?
    3. Why is it important for religious people to provide arguments for the existence of God if they already believe in him?

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