Most people immediately recognize Ludwig van Beethoven’s famous “Fur Elise.” As a young piano student, a much-simplified version of this classic piece was a core element of piano lessons. I ask you this question: Would Beethoven’s “Fur Elise” have been greater if Beethoven had only heard the melody in his imagination, or is “Fur Elise” made greater by the fact that Beethoven wrote the notes on a musical staff thus enabling later generations to enjoy his masterpiece? That is, if “Fur Elise” greater because it exists in reality instead of existing in Beethoven’s understanding alone?
Anselm of Canterbury seized this distinction between something that exists in the understanding alone and something that exists in reality to argue for God’s existence in his Proslogion. According to Anselm’s famous Ontological Argument, God is so great that if we can think of him, then it follows that God exists in reality. To understand this argument, we’ll need to understand a few concepts: First, we’ll examine what it means for God to be great. Then, we’ll examine what it means for God to exist in reality as opposed to in the understanding alone. According to Anselm, once we understand God’s greatness, we will see that to think that God exists in our understanding alone is to believe a contradiction.
God is great. For Christians, that phrase is so axiomatic that it borders on banality: In some places, when a Christians says “God is great,” they expect someone else to respond, “all the time.” However, when we claim that God is great, what exactly are we saying?
“Great” is one of those multivalent terms with too many meanings: I ate a great slice of pizza for lunch, heard a great song on the radio, and went to a great football game last weekend. Used in this way, the term “great” means that the noun it modifies—the pizza, the laptop, and the football game—pleases me in some way.
When I say that God is great, I don’t mean that God pleases me and is thus great; in fact, God’s greatness is independent of how I feel about him. When I say that God is great, I’m making a claim about his personality that I believe is true regardless of anyone’s opinion on the topic—including my own. As I understand it, greatness is a summary word for God’s various personality traits. Imagine “greatness” as an umbrella that covers multiple elements of God’s character, and you’ll see what I’m aiming for.
When I call God great, I mean that God has certain properties and characteristics which together constitute greatness. For example, God is great because he is loving. Leaving aside the important issue of whether or not this definition of divine greatness begs the question, we can all agree that the property of being loving makes something great. Imagine having an extremely annoying neighbor: Regardless of what you think would be more satisfying, would you be a greater person if you were loving toward them or if you killed their flowers while they slept? Obviously, you are a greater person if you show them love and kindness—especially if you don’t think they deserve it.
Similarly, God is great because he is patient: The property of being patient makes something greater. If I have a reputation for exacting vengeance on those who offend me, I would become a greater human being if, after a heart change, I began to show patience towards those who offend me.
Thus, when I say, “God is great,” I mean that he has many characteristics which, considered together, constitute greatness. Greatness is thus somewhat of a shorthand way of speaking about God and his characteristics.
Anselm seized this idea of greatness when defining the term “God.” According to Anselm, when we say “God,” we mean a being—perhaps I should say a Being—who is that “than which nothing greater can be thought.” In other words, we mean that God is that Being who holds all great-making qualities—such as being loving, merciful, kind, wise, compassionate, knowledgeable, fair, holy, logical, eternal etc.—to their greatest possible extent. Not only is this what Christians mean by God, everyone, even an atheist, whom Anselm calls the fool after Psalm 14.1 and 53.1, understands this definition.
With his definition of God as the greatest conceivable being in hand, Anselm switches gears and discusses whether this greatest being exists in reality or in the understanding alone.
Existing in Reality vs. Existing in the Understanding
To help you get a grasp on the idea of existing in the understanding, imagine writing a paper on your favorite book. Like any good writer, you know exactly what you want the paper to say before you write it. You understand the paper’s argument and form, premises and conclusions prior to writing. In a sense, then, the paper exists in your understanding prior to the writing process.
Another example of something that exists in the understanding would be a painting existing in the mind of an artist. Before she paints her picture, the painter has an idea of how the finished product will look. Thus, prior to painting, the painting exists in the artist’s understanding; once she paints it, however, the painting now exists in reality to be enjoyed by everyone.
With this distinction in mind, Anselm takes a crucial step: Anselm argues that if the atheist understands what Christians mean by God, then God exists at least in their understanding. That is, they have an idea of who God is.
The Atheist’s Problem
However, Anselm says that the atheist now has a problem. By definition, God is the greatest being. However, it seems that God would be greater if he existed in reality than existing only in the understanding. The reason is that things that are objectively good—such as God, love, mercy, compassion, patience, etc.—are greater in reality than in thought. For example, I would a greater person if I were kind to my wife than if I only thought about being kind to my wife. Similarly, Anselm argues that if God existed in reality, he would be greater than if he existed in the understanding alone.
This idea seems convincing: If God existed in my understanding alone, he would not be very great. He would, for example, lack the great-making qualities of independence, self-existence, and free will, to name but a few. However, if God exists in reality, he is independent, exists by necessity of his own nature, and can do anything he wants, even if he chooses to do things that we don’t like. This picture of God certainly seems to be greater than the one that exists in my understanding alone.
Now back to the atheist’s problem: If the atheist understands that God is the greatest being while also believing that God exists only in her understanding, the atheist is saying that the greatest being is not the greatest being, which is a contradiction. Since it would be greater for him to exist in reality than in the understanding, God, who is the greatest being, must, by definition, exist in reality.
Thus, according to Anselm, if we understand the definition of God as the greatest conceivable being, we must admit that God exists in reality.
Notes & Sources
 So that I don’t have to footnote the entire article, know that this argument appears in Anselm’s “Proslogion,” in Proslogion: With the Replies of Gaunilo and Anselm, trans. Thomas Williams (Indianapolis, IN: Hackett Publishing Company, 2001).
 Anselm, 7.