Proof for the Existence of God: An argument from a blog. - Part 2
Apologetics · Advanced
The Five Ways and the Divine Esse
Part Two: What Kind of Demonstration Is This?
Part 2 of 2 · AdvancedIn Part One we cleared away the usual misreadings and stated the Five Ways properly. They conclude to an Unmoved Mover, a First Cause, a Necessary Being, a Maximal Perfection, and a Supreme Intelligence.
But Aquinas ends each Way with a strikingly modest phrase: "and this all men call God." Not "and therefore the Blessed Trinity." Why the restraint? And does it leave him vulnerable?
There is a serious objection in the literature that says it does. Answering it requires understanding what kind of argument the Five Ways are. That turns out to be the most important question in the whole discussion.
Almost nobody reads Question 2 in order. They jump to Article 3 for the famous Five Ways and skip the two articles before it. But Articles 1 and 2 are where Aquinas decides what kind of proof is even possible, and everything downstream depends on it.
Is God's existence self-evident? Aquinas answers with a distinction. It is self-evident in itself (per se nota secundum se), because in God essence and existence are the same. But it is not self-evident to us (per se nota quoad nos), because we do not have access to the divine essence.
This is why Aquinas rejects St. Anselm's ontological argument. You cannot reason outward from what God is, because you do not have that to start from.
Can God's existence be demonstrated at all? Yes, says Aquinas, but only in one direction. There are two kinds of demonstration:
Propter quid — from cause to effect, from the nature of a thing to its properties. This requires knowing the essence first.
Quia — from effect back to cause. From what is better known to us toward what is prior in itself.
Since we lack access to the divine essence, demonstration of God must be quia. From effects. Always and only from effects.
Hold on to that, because it is about to do a great deal of work. Aquinas rules out reasoning from the divine essence before he states a single one of the Five Ways. It is not a concession. It is the architecture of the entire project.
Follow the Third Way one step further than it goes. It concludes to a being that exists necessarily. But ask the next question: why does it exist necessarily?
If this necessary being merely has existence, the way you and I have it, then existence is something it receives, something added to what it is. And whatever receives existence needs something to give it. We would be back in the very regress the Ways just closed.
So the being at the end of the Ways cannot merely have existence. Its existence must not be received at all. In it, essence and existence cannot be two things at all. It does not have existence. It is existence, subsistent being itself, Ipsum Esse Subsistens (ST I, Q.3, A.4; SCG I, c.22).
Here is where a genuinely serious challenge arrives, and it is worth stating in its strongest form rather than a convenient one. Some readers of Aquinas argue that the Five Ways only escape the regress problem because the essence/existence distinction is silently doing the work. On that reading, esse/essentia functions as a premise. And that sets up a dilemma.
If so, the Five Ways are not five independent arguments at all. They are five presentations of one argument, all resting on a single metaphysical claim.
The cost: one successful attack on that premise defeats all five simultaneously. Every egg is in one basket.
If so, they are exposed to the standard objections raised against each Way taken on its own, and they never actually reach the God of classical theism, only a first mover, a first cause, and so on.
The cost: the Ways prove less than the theist needs.
The dilemma looks tight. But it rests on an assumption that Aquinas himself has already ruled out.
The Five Ways do not presuppose that in God essence is existence. They arrive at a being of which that must be true. The identity is the destination, not the road.
Why must this be right? Because Horn 1 requires something Aquinas has explicitly forbidden.
If esse/essentia functions as a premise, then the argument reasons from the divine nature outward. But that is a propter quid demonstration, and Aquinas ruled it impossible in Q.2, A.1: we have no access to the divine essence.
A premise drawn from what God is would violate the epistemological constraint Aquinas imposes before he states the Ways at all. Horn 1 quietly asks Aquinas to do the one thing he says cannot be done.
So the difference between the readings is not merely presentational. It is a difference about what kind of demonstration the Five Ways are, and Aquinas answers that question two articles before he gives them.
And now the second half of the reply, which shows the Ways lose nothing by this.
Take the being the Ways establish: uncaused, unmoved, necessary of itself. Now suppose it merely has necessary existence rather than being existence.
Then its existence is something received. And whatever is received requires a giver, a prior cause of its existence-having. But the Ways have just established that this being is uncaused.
Contradiction. Therefore the being at the terminus of the Five Ways must be one whose essence is its existence. The esse/essentia analysis does not add a premise from outside; it makes explicit what the Ways had already implicitly reached.
If esse/essentia is a consequence of the Five Ways rather than a premise, then attacking it attacks a conclusion.
And you cannot undermine a demonstration by attacking its consequences. You must attack its premises. The dilemma dissolves because its first horn was never a real option for Aquinas in the first place.
- ST I, Q.2, A.1 — God's existence is not self-evident to us; we lack access to the divine essence.
- ST I, Q.2, A.2 — therefore demonstration must be quia, from effects to cause. The methodological anchor.
- SCG I, c.9 — the order of demonstration: from what is known to us toward what is known in itself.
- ST I, Q.44, A.1 — participation: whatever has being by participation is caused by Him who is being essentially.
- SCG I, c.22 — in God, essence and existence are identical. Stated as a conclusion reached after the demonstrations, not a premise assumed before them.
Notice the shape of the whole project. The Five Ways are the rational mind doing what natural philosophy always does: analyzing observable effects to press back toward the first principle. Each Way is one angle of that refinement. The esse/essentia analysis is the next stage of the ascent, not the ground floor.
This is the most common objection and it is a category error. The Ways do not conclude "everything has a cause, therefore God." They conclude that caused things require an uncaused cause; that things in potency require something in pure act.
God is not the biggest item in the series. He is what the series requires in order to be a series at all. Asking who made the Uncaused Cause is like asking what the bachelor's wife is called.
In an accidentally ordered chain, it can, and Aquinas says so. But the Ways concern essentially ordered series, operating right now, where the intermediate members have no causal power of their own.
Adding boxcars does not produce a locomotive. An infinite series of instruments, with nothing actually wielding them, explains nothing. The problem was never the length of the chain; it was the absence of a source.
Because the universe is exactly the sort of thing the argument is about. It changes, which means it has potency. It is composed of parts, and whatever is composed depends on its parts and on whatever unites them.
A necessary being in Aquinas's sense must be Pure Act with no potency and no composition whatsoever. The universe fails on both counts, on every page of physics.
The Ways are not a rival cosmology, and they never were. Aquinas denies that reason can prove the universe began. He would have been serenely untroubled by an eternal universe.
The question is not how the universe got started. It is why anything exists or changes at all, at this instant, and physics does not answer that; it presupposes it. Every equation in physics describes how things that already exist and already behave lawfully do so. The Ways ask why there is any such thing to describe.
It destroys Paley's watchmaker. It does not touch Aquinas. The Fifth Way is not an argument from complexity or improbability; it is an argument from the fact that unintelligent things behave lawfully and toward ends at all.
Natural selection is itself a beautifully end-directed, lawlike process. To invoke it is to supply another instance of exactly the phenomenon the Fifth Way is asking about, not to explain it away.
Correct, and Aquinas says so himself. That is precisely why each Way ends with the careful "and this all men call God" rather than a triumphant flourish.
Natural reason takes you to Pure Act, subsistent Being, the source of all perfection. It does not take you to the Trinity, to Sinai, or to an empty tomb. Those come by revelation. But this is not a failure; it is a foundation. Reason clears the ground and shows that the God who reveals Himself is not an irrational postulate but the very One that reason, pressed hard enough, was already pointing toward. Faith does not contradict what reason reaches. It goes beyond it.
- John F. Wippel, The Metaphysical Thought of Thomas Aquinas: From Finite Being to Uncreated Being. The standard scholarly treatment of the esse/essentia question. If you read one book on this, read this one.
- Reginald Garrigou-Lagrange, O.P., God: His Existence and His Nature. The classic Thomistic defense, and unsparing with objections.
- Aquinas, De Ente et Essentia, ch. 4 — the essence/existence argument in its own right, written early and stated with startling economy.
- Aquinas, Summa Contra Gentiles I, cc. 9–22 — the same terrain worked at greater length than the Summa Theologiae allows.
- Edward Feser, Aquinas: A Beginner's Guide and Five Proofs of the Existence of God — contemporary, analytically rigorous, and very good on the per se / per accidens distinction.
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