Thomas draws on a key insight from Plotinus: an uncausable entity must not just be simple—the fact of its existence must also be simple. Any compounding of elements in this fact creates the potentiality for causation. For something to be uncausable in the relevant sense, there must be a metaphysical explanation for its lack of a cause in any possible world. Obviously, this explanation cannot consist in something else’s causing it to be uncaused, so the source of uncausability must be intrinsic to the nature or essence of the uncausable thing. If the thing’s nature is such that the fact of its existence is complex, then we have failed to explain its uncausability, since a complex fact is a fact that could be caused: there could always be a cause of the unity of the elements that make up the fact.
We’ve already argued that neither strict actualism nor Lewis’s parallel-universe model is compatible with Thomas’s broadly Aristotelian commitment. In addition, neither model of actuality is compatible with the something’s whose actual existence is uncausable and per se necessary. In Lewis’s model, a thing might be uncaused in one world, but it will always have duplicates that are caused in other worlds. Similarly, for the strict actualist, there is no reason why something uncaused in the actual world couldn’t have a qualitative duplicate in some other world that is caused there.
Two of the five versions of inegalitarian possibilism are also incompatible with the existence of an uncausable, per se necessary entity, namely, the ostrich possibilist and the ostrich existential Platonist.
For the ostrich possibilist (the Ostrich Nominalist existentialist) account, we can always ask: what caused this or that thing to satisfy the primitive predicate actually exists? There is no way to single out certain things that are such that by their verry nature this fact could not be caused.
Similarly, the existential Platonic account, when combined with an ostrich-nominalist, primitively natural relation of instantiation, leaves us with no uncausable entity, since we can ask what caused the universal to stand in this primitive relation to itself. Moreover, this would seem to require the universal to cause its own existence, which we’ve seen to involve an objectionable kind of circularity.
That leaves us with just three remaining theories: the instantial-tie and state-of-affairs versions of existential Platonism and the act-of-existence theory.
There are only two plausible candidates for uncausability on the Platonic account with instantial ties: the universal of Actual Existence, or the instantial tie that links the universal of Actual Existence to itself. This results in an embarrassment of riches. It seems that the universal and the instantial tie are inter-dependent: the tie couldn’t exist without the universal, and the universal couldn’t exist with the tie. There doesn’t seem to be any plausible answer as to which is metaphysically prior to the other. So, neither is per se necessary.
The Platonic account with existential states of affairs is a somewhat more complicated case. The obvious candidate for uncausability would be the universal of Actual Existence. The fact of its actual existence would have to be a state of affairs that consists of the universal alone. This leads to a dilemma: either the AE universal by itself constitutes an existential state of affairs, or the existential state of affairs is some distinct entity that somehow contains the AE universal as its sole constituent. Neither horn of the dilemma can succeed. First, it’s impossible for something to be both a universal and a state of affairs. States of affairs are particulars. If the AE universal were itself a state of affairs, then it can’t also be a universal, something which, when combined with particulars, constitutes existential states of affairs.
But, second, if the AE universal and the state of affairs of its existence are distinct entities, then we can ask: what causes the AE universal to be a constituent of an existential state of affairs?
There is an additional problem with all of the Platonic accounts. The first three Ways establish the existence not just of an uncausable thing but of an uncausable efficient cause. A Platonic universal is not well-suited to play the role of the first efficient cause of particular phenomena.[1] This is precisely because a Platonic Form of existence must be the formal cause of all existing things, while the Thomistic First Cause must be the efficient cause of all other existing things. This is made especially clear by the First Way. Only something concrete and particular can be the cause of motion and change. A Platonic form of existence could be the formal cause of something’s existing, but it couldn’t be the efficient cause of its beginning to exist or ceasing to exist.
Therefore, only Thomas’s act-of-existence models offers a plausible candidate for intrinsic uncausability: namely, an isolated act of existence, one that does not formally actualize any distinct form, nature, or essence. If such an entity belongs to our domain of discourse, it cannot be contingent, since it is an act of existence, and (on the hybrid account) acts of existence have no counterparts in any merely possible world. An act of existence can be contingent only derivatively—by being the act of existence of a contingent substance or accident. Thus, a pure or absolute act of existence can’t be merely possible. If it exists, it must be necessary. It is uncausable because there is no further fact about the absolute act of existence responsible for making it actual. An efficient cause must actualize a thing’s potentiality to exist, but a pure act of existence has no such potentiality.
But how can an act of existence be absolute, without actualizing any form or essence? How can such a thing be an act of existence at all, if acts-of-existence are defined as those things which stand in the formal-causal relation to forms? We have to say that the act of existence which is the First Cause is an act-of-existence because it has the active potentiality to be the act of any essence or form whatsoever. In fact, it is not the act of any essence, but this does not deprive it of its character as an act of existence.
How does this argument compare with Anselm’s ontological argument? They are radically different. We can’t know by definition or stipulation that an absolute act of existence is even possible. For this we need the first three of the Five Ways, starting from the existence of finite things as a contingent fact. We can know that such a thing is even possible only by knowing that it is actual, because we infer the existence of an uncausable, per se necessary First Cause, and from the First Cause’s causal power and intrinsic uncausability, we infer that there is something identical to a bare, absolute act of existence.
In Summa Theologiae I, Q3, a4, Thomas offers the following argument for the identity between God and His act of existence:
Whatever a thing has besides its essence must be caused either by the principles of that essence (like a proper accident that necessarily accompanies the species—as the faculty of laughing is proper to a man—and is caused by the essential principles of the species), or by some exterior agent—as heat is caused in water by fire. Therefore, if the existence of a thing is distinct from its essence, this existence must be caused either by some exterior agent or by its essential principles. Now it is impossible for a thing’s existence to be caused by its essential principles, for nothing can be the sufficient cause of its own existence, if its existence has a cause. Therefore, that thing, whose existence is other than its essence, must have its existence caused by another. But this cannot be true of God; because we call God the first efficient cause. Therefore, it is impossible that in God His existence should differ from His essence.
He made a similar argument in De Ente et Essentia, paragraph 80:
But it cannot be that the existence of a thing is caused by the form or quiddity of that thing ─ I say caused as by an efficient cause ─ because then something would be its own cause and would bring itself into existence [in esse produceret], which is impossible.
If a thing has something beyond its essence, then this thing must be caused either by that essence or by something else. So, if God has existence as something “beyond” His essence, then either that existence is caused by the essence or by something else. However, God’s existence is absolutely uncaused. So, God’s existence cannot be “beyond” his essence. As Norman Kretzmann pointed out (Kretzmann 1997), this argument doesn’t show that God’s existence must be identical to His essence. It could be something entailed by His essence without being identical to it or caused by it.
Thomas goes on in article 4 to argue that the existence of a thing cannot be caused by its essence, since this would mean that the thing had caused itself to exist. For the essence to do any causing, the thing would have to already exist. Hence, the essence of a thing cannot cause the existence of that very thing.
But could the essence “entail” the existence without causing it? Aquinas is assuming (reasonably) that something can explain or entail the existence of a concrete thing with causal power only by causing it to exist. Hence, the essence of a thing cannot be the ultimate explanation for its existence.
- Assume for contradiction that God’s nature and God’s act of existence are distinct.
- If God’s nature and God’s act of existence are distinct, then they cannot be metaphysically independent of each other.
- If they are not independent of each other, then either the nature depends on the fact, or the fact depends on the nature, or both depend on some third thing.
- God’s existence cannot depend on anything.
- So, God’s nature must depend on the fact of God’s existence (i.e., on God’s act of existence).
- It is impossible for the existence of something to be metaphysically prior to its nature.
- So, God’s nature and God’s act of existence are identical.
- God is identical to His nature (from article 3).
- So, God is identical to God’s act of existence.
Thomas takes this identification of God with His act of existence to be confirmed by the Scripture, specifically, by Exodus 3:14, in which God reveals His name to be “I am that I am” or simply “I am” (in Latin: ego sum qui sum).
[1] In fact, these Platonic accounts are precisely the theory that Thomas rejects in Summa Contra Gentiles I, chapter 26: “That God is not the Formal Being of All Things.”
The Analytic Thomist 