One of the most popular criticisms of many proofs for God’s existence, and especially Aquinas’ five ways, are that they prove that a God exists, they do not prove that THE God of the Bible exists. Moreover, many think that these proofs do not prove that the God of Classical theism, i.e. an all-powerful, all-good, etc. God, exists.
The first criticism is correct, kind of. Any thoughtful Christian would tell you that proving that God exists does not prove that Jesus is that God. For that, we need to rely on historical, Scriptural, miraculous and prophetic evidence, among other things. But Aquinas’ arguments were not meant to prove the truth of Christianity. Rather, they were meant to establish the reality of God so that natural theology could get off the ground in the first place.
Now, the second objection, that Aquinas’ arguments do not even prove that the God of Classical theism exists, is at best a half-truth. While on their own they do not establish God’s goodness, power, or other divine attributes, they do provide us with the conceptual materials to do so. In fact, Aquinas used the definitions he proved in the five ways to get to the divine attributes of Classical theism.
Today, I am going to show a brief road-map for how the God of the Five Ways is also the God of Classical Theism, as outlined by St. Thomas Aquinas. This will obviously be cursory; I am going very broad brush-strokes on these arguments. But you will get the idea, and that is my goal today.
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Step 1: How the Five Ways Describe God
The five ways use a few different terms to describe God, each of which is compatible with one another. They are best described as aspects of God: they describe God in relation to one particular viewpoint, like according to how he actualizes all things, or how he is the explanation for all contingent things. Here is the short list of the descriptions of God from the Five Ways:
First Mover
First Efficient Cause
A Necessary Being
The cause of being, goodness, and every other perfection
Some intelligent being by whom all natural things are directed to their end.
While not explicitly listed in the five ways, Aquinas also argues that God is pure act,1 which is to say he is not just a being but being itself.
Step 2: God cannot change (Immutable)
The first three ways all posit God as the resolution to various infinite regresses. Since the infinite regresses described in Aquinas’ five ways cannot be resolved except by a being that does not pass from potency to act, and that passing just is the definition of change, God cannot change, which is to say that God is immutable.
Step 3: God is immaterial
But if God cannot change, then he cannot have a material body.2 This is because material bodies, by their very nature, are subject to all kinds of change. They can be divided. They can grow and shrink. They can move through space. All of these things are, in case you had not noticed, changes. So, if God cannot change, then he must be immaterial.
Step 4: God has no parts (simplicity)
When classical theists say God is simple, they do not mean that he is easy to understand, or unintelligent, but that he is not composite. He has no parts.
Aquinas shows this by pointing out that all composite beings are a) dependent in some way to their composing parts. If the parts separate or are destroyed, so is the composite being. But God is not dependent on anything, because he is the first being. Therefore, he has no parts.
Moreover, every composite being has a cause, because something had to compose those parts before (or at least logically before) the being itself existed. But God has no cause. Therefore, he has no parts.
Furthermore, there is act and potency in any composite being, because the parts are potentially separated. Moreover, if the composite being was composed in time, then the parts were at one time potentially combined. But there is no potentiality in God because he is the First Mover. Therefore, God has no parts.
Step 5: God is all-good (perfect or omnibenevolent)
Since God has no potency, then he has no privation. But all evil is a privation in a being that should not be there.
Moreover, since God is the cause all perfections in creation, he must be most perfect as the cause of those perfections that exist in creation.
Furthermore, God is pure act, which is to say that he is existence itself. And since, as Aquinas argues in Prima Pars Question 4 and I have argued elsewhere, existence and goodness are the same thing, God is all-good because he contains all of existence in himself.
Step 6: God is infinite
All limits are traits that a being has potentially. But since God has no potency, but is pure act, he must also be infinite.
Step 7: God is Everywhere (Omnipresent)
God holds all things in existence at every moment because he is the source of their existence. Therefore, as God is present in his work to all things because he is the source of their existence, he is present in all places.
Step 8: God is Eternal (Timeless)
God cannot change; he is immutable. But to move through time is to change. Therefore, God exists eternally, which is to say that he possess all of his existence at once in an eternal present.
You can read more about God’s eternity here in my series on God’s knowledge and Free Will.
Step 9: God is Omniscient (All-Knowing)
Since God holds all things in existence, is everywhere, and exists at all times at once in eternity, God knows all things in the Divine mind, including all things that could be.
Step 10: God is One (Unity)
God has no potency. But if there were more than one god, then it would necessarily be the case that there was something that one of the gods possessed in act that the other god only possessed in potency, otherwise there would be nothing upon which to ground the difference. In that case, either one would be God and the other(s) would not, or both (all) would fail to be God. But there can only be one God.
Thus ends my speed-run of the divine attributes. Thus, while it is the case that the five ways do not prove everything classical theists claim about God on their own, they provide the conceptual framework for all of the attributes of God. Indeed, Aquinas moves to proving these attributes immediately after proving God’s existence in the Summa Theologiae.
My point is not necessarily that these arguments are watertight as presented. But the criticism that arguments for God’s existence do not, at least, provide the materials to go further in understanding God’s nature is misplaced. The scholastics had an investigation into God’s nature explicitly in mind when they proved God’s existence. They were not added in later ad hoc.
Moreover, this shows that God’s attributes are not arbitrarily picked as cool things to think about God or even plausible theories. Rather, they hang together as parts of a full metaphysical system by which we can know quite a bit about God. To deny one is tricky, because it requires the denial of some important fact about God’s existence. It should not be done lightly. Those models that deny one or more of these traits are commonly called theistic personalism, and I tend to think they are reckless to hold. But that is for another post.
Looking to ground your thought in the Catholic Intellectual Tradition? Not sure where to start? You are not alone. I built a reading plan to get you from “beginner” to “Amateur Catholic Philosopher” in just a year. Check it out here:
For an introduction to the act/potency distinction, read this: The Sense in Which You Are Purple
Save your “what about Jesus?” questions for another post. It is a good question, but it is a matter of Christology, which is too far afield for this post.
I’m grateful for the clarity of your roadmap here — it’s helpful to see how the Five Ways connect to the attributes of classical theism.
As I was reading, I kept turning over the phrase "natural theology." When Augustine speaks of creation bearing witness, or when Aquinas begins from motion and causation, I sometimes wonder whether they mean something more integral by “nature” than we tend to mean today. Not simply the abstraction “the created world,” but a reality already experienced as beautiful, intelligible, ordered, and speaking.
I find myself asking whether we modern readers even fully share that sense of what “creation” is. Do we still perceive the world as something given and meaningful in itself, prior to analysis? Or do we begin from abstraction and move outward?
Your post stirred that question for me in a good way. I’d love to keep thinking along these lines — these are conversations worth having.
I like how clearly you walked through this, Alex. It felt simplistic enough yet also very insightful. I especially liked your explanation of simplicity. The point about composite beings depending on their parts, and how that would undermine God being first, made the idea much more concrete. The section on goodness also stood out to me. Tying goodness to existence itself, rather than treating it as just one trait among others, really clarifies why omnibenevolence is not just added on later.