Mormons and Catholics believe in two different Gods. Both call God the Father, the Son, and the Holy Spirit, but each means a totally different thing from the other.

In Catholicism, God is three persons in one divine nature. God is immaterial and absolutely simple. In Mormonism, the three persons are distinct in substance and essence. They are made of material and exist in a material world.

There are many issues we could focus on, like the “three gods or one God” issue, or how Christ must be equal to the Father, but if we did, we would simply be talking past Mormons. The differences are not semantic. If we want to break any ground with Mormons, we must look to the roots of reality; Catholicism and Mormonism explain existence in completely different ways.

In Catholicism, God created everything ex nihilo (from nothing). He brings everything into existence, and all existence is contingent on him. God is the uncaused cause—the ultimate explanation of all things.

In Mormonism, God does not bring all things into existence from nothing. Instead, he organizes eternally existing matter. This matter has existed forever, and all things, including god, are made by it (Abraham 3). This view, Mormons argue, gives us a more realistic grasp on reality. It is concrete. It avoids the confusing idea of creation from nothing and explains reality in a way we can more easily understand.

Regardless of how concrete an idea is, the question remains: is the Mormon view a sufficient explanation for why anything exists at all? It is not. Eternal matter cannot explain its own reason for existence, let alone existence itself. Only a theology where God is the very act of being can explain reality fully.

Existence as Act

This is precisely what the Thomistic framework describes. It begins with the distinction between essence (what a thing is) and existence (that a thing is). A circle has a definable nature—it’s a circle. A human being has an essence. But neither must exist; their existence does not explain itself.

St. Thomas Aquinas teaches that whatever does not have existence of itself must receive it from another. Thus, if everything has a finite essence distinct from its existence, then something else must be the cause of its existence (Summa Theologica, Prima Pars Q2). A causal chain cannot regress infinitely while providing any satisfactory answers about existence. There must be a being whose essence is the same as its existence—a being that is existence itself.

This, Aquinas says, is actus purus, pure act. This is the trinitarian God, a being without composition, limitation, or dependency. He is the cause of all existence, not merely one being among others. All existence ultimately depends on him.

Thus, creation from nothing is necessary. All things are radically dependent on God for their existence. He didn’t create us, then forget about us or let things happen. He is the source of all things.

This means, when compared to Mormon theology, something like matter cannot be uncreated. It must receive existence from somewhere.

Mormon Material

Mormons disagree. They posit an entirely different system of reality. Matter is eternal and does not depend on anything for its existence (D&C 131). God does not create or sustain matter, but organizes and structures it.

From an Aristotelian standpoint, eternal matter is the material cause, whereas God is the efficient cause, shaping pre-existing matter into the forms we see today.

Mormons tout this as a far more understandable and realistic explanation for existence. Afterall, Mormons are right to say that creation from nothing and a God without parts or passions is difficult to comprehend. We cannot comprehend a being who exists outside time and has no parts or passions, but we can comprehend a sculptor who forms David out of marble.

But comprehensibility does not mean likelihood. Mormonism’s explanatory adequacy is dependent on whether organization from eternal material can suffice as the ultimate explanation for existence.

Insufficient Explanation

From a Catholic perspective, eternal matter does not explain existence, but postpones the question of why this material exists at all. Mormonism’s answer is that it is necessary.

But simply declaring something material as necessary does not make it so. Since material cannot explain its own existence, an explanatory demand persists.

This is what’s known as the principle of sufficient reason: whatever exists must have a sufficient explanation for its existence. Mormon theology rejects this, and ultimately looks toward brute facts (facts that exist without further explanation) at the foundation of existence.

The problem with allowing brute facts to be the fundamental answer for existence is that explanation itself becomes arbitrary. If reality is at bottom unexplained, why do any explanations matter at all? Why bother looking for answers?

Although brute facts give Mormonism internal consistency, it is an insufficient explanation for existence. It leaves many questions unanswered. It also opens the door for worrying consequences: if God is ultimately not the source of all existence, how can we trust that he will sustain ours?

We can’t—at least not in the same way we can in Catholic theology. If we accept the brute fact that matter must exist without further explanation, we must blindly trust that existence will continue in that substrate. There is no real explanation for why it must.

The Trinity Is True

Catholic theology leaves no such door open. Since God is existence itself—and is all good—we have fully explained reasons to trust him to continue our existence.

Ironically, the lengths to which Mormons go to make God knowable create a less succinct and less understandable existence.

Though we can’t say Mormonism is impossible, just as many strange ideas aren’t, we can ask which explanation of reality is more likely: a fully material existence where one must accept the brute fact that that’s simply how things are, or a God who is the cause of all creation and the ultimate explanation for all things?

The Trinity is far more likely. It requires far fewer assumptions to accept, and it results in a God we can absolutely trust without deferring blindly to brute facts. All existence must be accounted for. If there is to be a complete answer to the question of why there is something rather than nothing, it can be found only in that which is existence itself.