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What Is Divine Simplicity?

The doctrine of divine simplicity can be an asset in defending the existence of God to a secular world

Trent Horn

What is God’s most fundamental attribute? You might say it’s his goodness, or his power, or his knowledge. But there is one thing about God that makes him “God” and not just another creature: his simplicity.

I don’t mean that God is simple to understand, but that God is the most fundamental aspect of reality. There is nothing beyond God that serves as the foundation for all existence, and in order to be that foundation for all of reality, God must be simple, or not composed of parts. St. Anselm of Canterbury put it this way: “[T]here are no parts in you, Lord: neither are you many, but you are so much one and the same with yourself that in nothing are you dissimilar with yourself.” Almost a century later the Fourth Lateran council began its confession of faith by saying:

We firmly believe and simply confess that there is only one true God, eternal and immeasurable, almighty, unchangeable, incomprehensible and ineffable, Father, Son and holy Spirit, three persons but one absolutely simple essence, substance or nature.

All of the attributes we are familiar with, like God’s unlimited knowledge, goodness, and power, flow from the fact of his simplicity. The contemporary Eastern Orthodox theologian David Bentley Hart says of divine simplicity:

There is an ancient metaphysical doctrine that the source of all things—God, that is—must be essentially simple; that is, God cannot possess distinct parts, or even distinct properties, and in himself does not allow even of a distinction between essence and existence . . . if one believes that God stands at the end of reason’s journey toward the truth of all things; it seems obvious to me that a denial of divine simplicity is tantamount to atheism. (The Experience of God, 128)

Many of the classical arguments for the existence of God naturally lead to the conclusion that God is not composed of parts. For example, if God is necessary then he cannot depend on anything else in order to exist, including anything that unites his parts into a single whole. If God is pure act and the source of all change, as the proofs of St. Thomas Aquinas show, then God cannot possess any potential within parts that can be actualized.

Many modern theologians and philosophers are, however, skeptical of this doctrine. They claim that if God is not composed of parts then all of his properties like omniscience and omnipotence could not be separate from one another. This would mean God’s knowledge is identical to his power, which doesn’t seem to make sense.

But the problem with this objection is that when we talk about God’s nature we always speak in analogies because God is so unlike us. Saying God has “properties” of being “all-knowing” or “all-powerful” doesn’t mean he has concrete things like “omnipotence” that we don’t; it is a way of saying God isn’t limited in knowledge or ability. Catholic philosopher Edward Feser puts it this way:

When we say that God has power and knowledge (for example) we don’t mean that He instantiates the properties having power and having knowledge, just as we do. We mean that there is something in Him that is analogous to what we call “power” and “knowledge” in us, but that whatever this amounts to, it does not amount to his “having” just the same thing we do, or instantiating “properties,” or being a substance in which various distinct attributes inhere, etc.

But wouldn’t God be divided into parts based on all the different truths he knows? No, because God knows all truths as a unified whole. To make an analogy, you could write down pages of truths about a chair: its height, weight color, sturdiness, etc. But you could also know these truths by just beholding an image of the same chair. God’s knowledge is similar in that it isn’t divided into parts but exists as a perfect whole.

Another objection is that divine simplicity contradicts the Trinity, or the belief that God exists as three persons. But God is not divided into three persons—the Father, Son, and Holy Spirit all fully possess the one infinite divine nature. They differ from each other only in their relations, not in their being or essence. God who is pure being itself is made fully known through each member of the Trinity.

Understanding God’s simplicity helps us understand God’s other fundamental attributes. For example, God’s simplicity entails his attribute of being infinite. Now, when we say that God is infinite, we don’t mean that God has an infinite number of thoughts or that he extends over an infinitely long cosmic distance like an infinite series of numbers. Instead, something is infinite if it doesn’t have any limits. God is the absolutely simple ground of being itself, and so nothing limits him or his attributes. Instead, God determines the limits of everything else.

It follows from God’s simplicity and his infinity that there is only one God. Think about it: if what makes God “God” is the fact that he is not divided or limited in any way, then there could not be more than one God. If there were more than one God, then both of those beings would have to limit each other in some way, thereby negating each of their claims to being infinite. Each of them would have to lack something the other had in order to distinguish between them as separate beings.

Finally, divine simplicity helps us understand God’s goodness. The atheistic philosopher Stephen Law has argued that there is no way to know if God is good based on the universe God created. From Law’s perspective, the world could be the product of a good god that tolerates evil in order maximize goodness or the product of an evil god that tolerates goodness in order maximize evil (e.g. evil people are more evil when they afflict especially virtuous people).

But God’s goodness isn’t an arbitrary quality, it is an essential aspect of what it means to be God precisely because of his simplicity. Since evil is not a thing itself but is rather an absence of being (like cold is just the absence of heat), and because God exists without limit or deficiency, it follows that God must be good because infinite being cannot lack anything. The Catechism of the Catholic Church cites St. Thomas Aquinas in teaching that “God’s almighty power is in no way arbitrary: ‘In God, power, essence, will, intellect, wisdom, and justice are all identical. Nothing therefore can be in God’s power which could not be in his just will or his wise intellect’” (271).

Like God himself, God’s simplicity can be difficult to comprehend, but it makes sense if we believe God is not merely a being with unlimited powers, but is infinite being itself. It’s false to say God is “this kind of being” or “that kind of being.” God just is being or he simply “is.” If God had distinct parts, then we would wonder what unites his parts together into a single whole. For example, the different parts of our bodies are unified by our souls. If God had parts that would mean there is something more fundamental than God that allows him to exist. But if God needed something else in order to exist then he wouldn’t be God.

Therefore, the doctrine of divine simplicity should not be seen as a medieval belief that is a liability for Christians, but one of our best assets in defending the existence of God to an increasingly secular world.

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