Does the God of classical theism exist? The principal reason for thinking that God fits the profile defined by classical theism is this: we have good metaphysical grounds for believing both that some entity that fits this profile exist, and we have good theological grounds for believing that, if such an entity exists, it must be identical to God, that is, to the God of the Bible, the God of Abraham, Isaac, and Jacob. 
 
So, what is the profile of the God of classical theism? There are four crucial characteristics:
 
1.God is absolutely the first cause of all causable things.
2.God is atemporal.
3.God lacks any intrinsic, passive potentiality.
4.God has no distinct nature and no distinct act of existence: He is identical to His own act of existence, which is also His nature or essence.
 
It is noteworthy that this list does not contain any of the traditional omnis: omniscience, omnipotence, or omnibenevolence. I haven’t included personality on the list, nor such properties as having knowledge or will. I haven’t included God’s infinity or perfection or uniqueness. This is not because classical theism is silent on any of these points, but because, in the classical-theist tradition, all these divine characteristics follow from the four that I have listed. They are, from an epistemological point of view (that is, in the order of human understanding), secondary characteristics of the God of classical theism. These secondary characteristics are not points of controversy between classical and non-classical theists; in contrast, all of the primary characteristics on the list are quite controversial.
 
There are, therefore, two tasks which the classical theologian must complete: first, to argue successfully that some entity satisfies the four primary characteristics, and, second, to demonstrate that any being with the primary characteristics must also have the familiar secondary characteristics.

A central thesis of Thomas’s natural theology is the claim that God is a being of pure actuality—meaning that God is utterly lacking in passive potentiality. This follows quickly from the fact that God is absolutely the first cause, in the sense of being the cause even of other necessities. God is the only being that is necessary in Himself. In order to act as first cause, God must be in His very essence fully equipped with a complete complement of intrinsic properties. If He were not, then there would be a component of contingency or at most conditional necessity in His intrinsic state as the first cause, but any such component would require a still more primary cause, contradicting God’s status as absolutely first.
 
God lacks only passive potentialities: He possesses active potentialities (i.e., active powers) to the greatest possible degree. God can cause anything that is metaphysically causable—His active power is without limit. If it were limited, then this limit would require some cause, again contradicting God’s status as first cause.
 
God is, moreover, maximally free. He was free, in particular, to create nothing at all, or to create any cosmos that would be a fitting expression of His nature. There are many such possible cosmoses. Ours is just one. Hence, our cosmos is thoroughly contingent.
 
How is the contingent exercise of active power on God’s part consistent with His lack of passive potentiality? In Aristotelian metaphysics, there is no conflict, since the exercise of active power is an action, and an action takes place in the patient, not in the agent. God does not have to modify Himself in order to exercise His active power. He does not have to deliberate or plan, and His intentional action requires no internal representation in His mind. The truthmaker for God’s intentionally creating creature x is simply the existence of x itself. No difference internal to God is required to differentiate worlds in which God creates x from worlds in which He does not.
 
But, a critic may respond, isn’t God identical to His own action, given Thomas’s strong doctrine of divine simplicity? If so, the objection goes, since God exists necessarily, His action must exist necessarily, in which case everything that God creates must also exist necessarily.
 
It is true that Thomas embraces the thesis that God is identical to His own action. In Summa Contra Gentiles, I, chapter 45 and in Summa Theologiae I, Q14, article 4, Thomas argues that God’s act of understanding is identical to His essence. Since He is identical to His own essence, God is identical to His act of understanding. In Part II of the Summa Contra Gentiles, Thomas claims both that God’s power is identical to His own substance, and that His action is identical to His power.
 
Ordinarily, the act of a power is distinct from that power. So, if I whistle a tune, my particular act of whistling is obviously distinct from my power of whistling. However, in God’s case, His act of understanding is identical to His power of understanding, and both are identical to God Himself.
 
The act of a power is the perfection of the power. A power that isn’t exercised is imperfect. So, if God’s act were distinct from His power of understanding, then that act would perfect His power. Furthermore, the perfecting of this power would be the perfecting of God’s essence. Hence, God’s perfection would depend on something other than God, which would contradict the fact that God is infinitely perfect. God’s act must be identical to God, so that it is God who perfects Himself.
 
An act stands to a power as actuality to potentiality. So, if God were not identical to His act, then His power of understanding would have a potentiality that is actualized by His act. But God has no passive potentiality. He doesn’t stand as potential to anything else. So, He must be identical to His own act.
 
The Modal Collapse Argument
 
Many critics of Thomas argue that he is committed to God’s willing necessarily everything that He wills, because of Thomas’s strong doctrine of divine simplicity. The argument typically goes something like this:
 

1. God exists necessarily (Third Way)
2. God is identical to His act of willing (Divine simplicity – SCG I.45 and II.9)
3. God’s act of willing is identical to His act of willing to create this universe.
4. So, God’s act of willing to create this universe exists necessarily. (From 1, 2, 3 by the law of identity)
5. So, God necessarily wills to create this universe. (From 4?)

 
The argument is guilty of a fallacy of equivocation. Understood in one way, the term “God’s act of willing to create this world” picks out something that exists necessarily, namely, God Himself. Understood in a second way, the term picks out something that exists only if this world exists. On either meaning, conclusion 5 does not follow from sub-conclusion 4. On the second meaning, the phrase “God’s act of willing to create this universe” is actually a kind of quantifier: “There is something that is uniquely an act of willing by God to create this universe and…”
 
To make clear why 5 does not follow from 4 using the first meaning, the inference to 5 on that reading requires an additional assumption:
 
4b. God’s act of willing to create this universe is essentially God’s act of willing to create this universe.
 
On the first reading, assumption 4b is false. God’s actual act of willing (which is in fact an act of willing that He create this world) could have been an act of willing that He create a different world, or no world at all. Consider, for example, a parallel proposition:
 
BD. Ben’s father is essentially Ben’s father.
 
Not true—although I am in fact Ben’s father, there are possible worlds in which I have no children at all.
 
Critics of Thomas will complain that the cases are not parallel. Assumption 4b just must be true, because every act of willing has its own object essentially. My choosing a chocolate cookie for a snack could not have been my choosing an oatmeal cookie. Different objects necessarily imply different acts of will. However, this is wrong, for two reasons. First, because God is different from creatures. God does not have to undergo any kind of process of deliberation in order to make a choice. Hence, He and His act of will are exactly the same in every possible world. They have different objects in different worlds, but this difference is merely a Cambridge difference in God—it doesn’t require any internal modification. The objects of God’s choosing are immediately present to God as chosen by Him—they don’t have to be re-presented within God as chosen.
 
Second, even in the case of human actions, it is possible for the same act of human willing to have different objects in different worlds. I’m thinking of a case of spontaneous but voluntary action—acts taken without any prior deliberation, but which are nonetheless guided by the human will. Consider, for example a musician who is improvising as he plays, or a speaker who is speaking very rapidly. The notes or words that are chosen are chosen by will, and yet there need be no prior mental event guiding the action. The action has “voluntariness”, as Elizabeth Anscombe puts it, without being the product of some internal volitional event. In a different possible world in which the person chooses a different note or different word, there may be no internal difference despite the fact that a different choice was made. Consequently, there is no reason to deny that the very same act of will could exist in both worlds.
 
Let’s return to the argument and consider using the second meaning. On that interpretation, steps 4 and 5 look like this:
 
4c. There is something that is uniquely an act of willing by God to create this universe, and that thing exists necessarily.
5c. There necessarily exists something that is uniquely an act of willing by God to create this universe.
 
Again, 5c does not follow from 4c, unless we assume that anything that is in this world an act of willing by God to create a certain universe must be an act of God to create that same universe in every possible world in which it exists. Again, we have to assume that God’s act of willing is essentially an act of willing to create this universe specifically. And that Thomas will deny.

This is the crux of Thomas’s whole natural theology—it is the main conclusion toward which the first Four Ways point, and it is the fulcrum from which Aquinas moves our theology toward God’s perfection and infinity. In this respect, Aquinas’s natural theology is unique. I don’t know of anyone, earlier or later, who proceeds in the same way. Duns Scotus, for example, drops the First Way entirely and relies primarily on God’s infinity, deduced from his version of the Second, Third, and Fourth Ways.
 
In his masterful The Metaphysics of Theism, Norman Kretzmann elucidates Thomas’s arguments in Book I of the Summa Contra Gentiles. In the chapter on simplicity, Kretzmann distinguishes two “interpretations” of Thomas’s claim that God’s essence is His existence: the cautious and the bold. On the cautious interpretation, we claim only that God’s essence entails (all by itself) that God exists. On the bold interpretation, we claim that God’s essence is identical to His act of existence. Kretzmann recognizes that Aquinas clearly endorses the bold interpretation. The only question is whether his arguments support this bolder and stronger claim.
 
Kretzmann begins with the argument that he calls G6, which is a version of Aquinas’s Third Way. So, let’s assume that God is that thing which is necessary per se and not through another. Kretzmann suggests that a being whose essence entailed its existence would qualify as necessary per se. He compares the existence of God with the existence of certain mathematical entities, like the number zero or the empty set, whose nature seems to guarantee that they “exist” in some sense in every world. Yet clearly in none of these cases are the essences identical to their act of existence.
 
Kretzmann thinks that Aquinas’s strongest argument for the bolder claim is the argument from potentiality and actuality. That is, if we think of essences as representing the potential existence of something, and the act of existence as the actuality of that potential, then essences must be thought of as passively receiving existence from something else. Since a thing can’t exist until its essence has received such existence, nothing of this sort could be uncaused. Therefore, since God is uncaused, His essence cannot receive existence. So, He could exist only if His essence already was an act of existence.
 
Of course, this presupposes that we have accepted the essence/existence to potentiality/actuality correspondence. This turns, I think, on seeing Thomas’s theory as a theory of actuality. It is acts of existence that actualize possibilities. Mere essences, sans such acts, are thus mere potentialities for existence.
 
In addition, one could question Kretzmann’s claim that something could be necessary per se by having an existence that is “entailed by” but not identical to its essence. His examples are mathematical, and one could argue that such mathematical things derive their necessary existence from God. If God were not the ultimate, necessarily existing Mathematician, could things like numbers or sets really exist?
 
And, in fact, do numbers and sets exist at all, in the relevant sense. We are looking for something exists necessarily and without cause, and which exists with the causal power to create other things. Mathematical objects are causally inert. Alexius Meinong suggested that they merely “subsist” in a shadowy realm of mental objects, in contrast to the full-bored existence of God and concrete creatures. Arguably, the existence of something could be explained by an essence only by being caused by it. So, if God is uncaused, His existence cannot be explained or “entailed” by His essence, unless they are one and the same thing.
 
1. God is identical to His own Essence (SCG I.21 and STh Q3 a3)
 
The first step in Aquinas’s argument is to suggest that God is, in a way, identical to His own form, as are angels. In fact, this already follows from the fact that God contains no matter, as Thomas argues in the Summa Theologiae. Without matter, there is nothing in God to individuate Him from other things with the same kind of form. Hence, God must be identical to His form simpliciter.
 
In the SCG, Thomas also appeals to the fact that God lacks composition. If God were not identical to His own essence, then there would have to be something (matter or accidents) that have been added to His essence, resulting in His having “parts” of a kind (i.e., metaphysical parts).
 
He also argues (in par. 5) that, if something is not identical to its form, then that form is a kind of cause of the thing. The thing would then depend for its existence on the form. Since God depends on nothing, He must be identical to His own form, and so to His own essence.
 
In par. 6, he appeals to the potency/act distinction, arguing that whatever is outside an essence is a mere potentiality that is actualized by the essence (or form). I think the picture is that the parts of things (matter, accidents) that are not identical to a form receive their existence through the form. But, since God contains no passive potentialities (chapter 16), He must be pure form/essence.
 
2. God is identical to His own act of Existence (SCG I.22, STh Q3 a4, De Ente par. 80-3)
 
In the Summa Theologiae, Aquinas proves that God’s essence is identical to His existence. Since we have already established that God is identical to His essence, this entails that God is also identical to His act of existence.
 
The main argument appeals to causation. 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 Kretzmann pointed out, 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 entailed 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.
 
Aquinas’s second argument is the appeal to potency and act that I discussed above.
 
In his third Summa Theologiae argument, Aquinas argues that if something has existence but is not its own existence, then it enjoys only “participated” (i.e., caused) existence. This is I think an appeal to the Fourth Way. The highest form of existence would be to be simply identical to pure, unadulterated existence. This would be possible only if one’s essence was identical to one’s existence.
 
In SCG I.22, paragraph 2, Aquinas argues in the following way. First, he shows that God’s essence must be compatible with existence. Given that, Aquinas argues that there are just three alternatives: either God’s existence depends on His essence, or both depend on some third thing, or the essence must depend on the existence. One might push back: why couldn’t both the existence and essence be independent, uncaused things? I think that Aquinas would argue that, whenever essence and existence are distinct, then the two must be dependent on each other, or on some third thing. An essence depends on the existence in order to exist, and the existence depends on the essence for its identity, tied as that is to the character of the thing whose existence it is.
 
If God’s existence depended on His essence or some third thing, then God’s existence couldn’t be uncaused, contrary to the Second and Third Way. So the case to consider is that in which God’s essence depends on His existence. However, if God’s essence could depend on God’s existence, then we could make sense of God’s existence without considering His essence. Here again we have to turn to the actuality/potentiality distinction. If essence and act of existence are distinct, then the act of existence must actualize the possibility represented by the essence. The act of existence cannot both bring into being a possibility and then actualize that some possibility. An act of existence cannot do anything prior to its actualizing of an essence—it is only after actualizing an essence that it can be said to have a nature that could bring about anything.

 All of Aquinas's Five Ways depend, in one way or another, on ruling out the possibility of infinite causal regresses. In the version of the First Way (the argument from motion) in the Summa Contra Gentiles (I.13), Aquinas follows Aristotle in offering two separate arguments against the causal regress. In the first three ways in the Summa Theologiae, he offers just one of the two Aristotelian arguments: an argument that depends on what I call the No-Intermediate-Real-Cause thesis. This is a thesis that states that if x is a cause of y, and y is a cause of z, then y is not really a cause in the strict sense but only secundum quid (only in a manner of speaking). An intermediate link in a causal chain is not in any sense the source of the reality of the ultimate effect--it is merely a conduit through which the first cause acts. Therefore, an infinite regress is impossible, because (as Aristotle and Aquinas note) every link in the regress would be only an intermediate cause. Hence, such a regress cannot contain any real causation.
 
This is a plausible argument, despite the fact that it is often dismissed as based on a fallacy of equivocation. The standard objection (going back at least to Cajetan, I believe) is that Aquinas equivocates on the phrase "removing the first cause." If we have a finite chain and we hypothetically remove the first cause from the series, it is obvious that none of the intermediate causes can act. Aquinas asserts that if we consider any infinite regress, we have a situation from which we have (in a sense) "removed the first cause". But, as critics point out, in this case there never was a first cause to be "removed", and so the cases are incomparable. However, Aquinas real point is simply to claim that intermediate causes are never causes in their own right but are always wholly parasitic on the first cause. Given that assumption, infinite causal regresses are indeed impossible.
 
The other strategy for dealing with infinite regresses was invented by Avicenna, followed by Scotus, Leibniz, and many subsequent thinkers (including me in 1997). This is the Aggregation Strategy. The Aggregation Strategy concedes, for the sake of argument, that infinite regresses are possible. However, the Strategy insists, if a regress consists entirely of contingent (or finite) things, then we can aggregate the whole series into a single entity and insist on a cause for it. Start now with a single finite thing, and consider all of the finite causes of that thing (whether immediate or remote). Either this series terminates in an uncaused thing, or else it constitutes an infinite regress. In the latter case, we can demand a cause for the whole series. This cause must be infinite, since any finite cause of the series would be a cause of the original entity and so would already be included in the series itself. A member of the series cannot cause the whole series. An infinite thing cannot be caused. And so we reach an uncaused first cause.
 
Aquinas was aware of this strategy, through his close reading of Avicenna. Why didn't he adopt it? I think he was worried that not all infinite series can be aggregated into a single entity. If an infinite series consists of entities of the same species (or a finite number of species), then it has the characteristic that Aquinas labels being accidentally infinite. An accidentally infinite series can be aggregated and must be caused as a whole. This is why Aquinas can concede that accidentally infinite series might exist without losing the force of his first cause argument. However, if an infinite series consists of entities of an infinite number of species, with the species climbing progressively higher and higher in the Great Chain of Being, the Aggregation Strategy could not be convincingly applied. Aquinas would call such a series essentially infinite, and he must (if the Second or Third Way is to work) deny the metaphysical possibility of such a series. This is why he appeals to Aristotle's argument and what I call the No-Intermediate-Real-Cause thesis, which should now be applied only to series that rise "vertically" through the ontological order of species.

​Aquinas's second way, the way of efficient causation, had perhaps the most influence on subsequent natural theology. It has counterparts in the work of Scotus, Leibniz, and Samuel Clarke (to name a few), and it is the argument that Kant labels "cosmological" in the First Critique. I am going to assume the argument that Aquinas develops in chapters 3 and 4 of De Ente et Essentia is an elaboration of the second way. The argument's form is quite simple:
 
1. Some things actually exist (as known primarily by sense perception).
2. Every finite thing (i.e., thing for which there is a real distinction between essence and existence) that actually exists has an actually existing cause of its existence.
3. Causes are prior to their effects in the order of actual existence.
4. Every chain of causes has an essential structure.
5. The essential structure of every chain of causes is finite (has terminal, uncaused nodes).
6. Therefore, there exists at least one actually existing infinite being, and every finite thing is caused by one or more such beings.
7. There can be no more than one infinite being.
8. Therefore, there exists exactly one actually infinite being, which is the ultimate cause of every finite being.
 
If something has actual existence, and this actual existence is something distinct from its essence, then there is some part of the thing's essence which is disjoint from its existence. The finite thing's existence depends on a joining or combining of its existence with the remainder of its essence, and this joining or combining must have some explanation. It cannot be explained by the remainder of the essence, since, it it were, the thing would be a cause of itself (contrary to premise 3). It cannot be caused by the thing's actual existence, since a thing's existence cannot be prior to any part of its essence, since every 'act' or 'event' of existence depends for its very identity on the essence that it actualizes. Hence, the only possible explanation for this joining or combining must appeal some distinct entity (its efficient cause).
 
In contrast, if a thing's existence is identical to its essence, no explanation of its existence is needed or even possible. The essence of a thing constitutes its possible existence, and if a thing's existence is identical to its essence, then that thing's actuality is identical to its possibility. Hence, we cannot sensibly ask how or why its possibility has been actualized. For such a thing to be really possible is for it to be actual, and vice versa. If such a being exists at all, it must exist with absolute necessity. For this reason, the causal principle (premise 2) must be limited to finite things.
 
Premise 7: There can be only one infinite thing (so defined). Suppose that there were two. We can ask whether it is possible for one to exist without the other. If so, then one or the other exists only contingently, which we've have shown to be impossible. So, it must be necessary for both to exist and to relate to each other as distinct entities. Is this relation of distinctness contained in the essence of one or both? It couldn't be just one, since, if it were, the other would depend for its existence on the other. So, the relation must be contained in both essences. But this would introduce some complexity into both essences, which means that we could no longer identify either essence with a simple act of existence. In addition, there would have to be some explanation of the symmetry. Each would have to depend essentially on the existence of another, again contrary to their simplicity and uncausability.
 
This leaves us with premises 4 and 5, which jointly rule out the possibility of an essentially infinite regress.  I will take up this crucial question next time.

I've recently discovered that my views on prime matter as the universal individuated can provide new support for the real distinction between essence and existence. As I've explained in earlier posts, I believe that packets of prime matter are the ground for any numerical distinction among substances of the same species, whether those substances exist at the same time or at different times. Imagine, for example, a sempiternal world with an infinite past and infinite future. Let's suppose that Nietzsche's eternal recurrence is realized in this world, so that there are an infinite number of distinct but indiscernible Napoleon Bonapartes, one for each cycle. Each temporal stage one each Bonaparte has its own, unique packet of prime matter. It is the distinctness of these packets that ground the distinction between different Bonapartes, and it is the distinction between the Bonapartes that distinguishes the accidents of time during which they exist.
 
This individuating role of prime matter extends also to merely potential beings. Consider, for example, some merely potential pair of identical twin daughters of my wife and me (we did not in fact have any such twins). There are surely some potentially existing pairs of twins, and, within each pair, each twin must be numerically distinct from the other. This numerical distinction between potentially existing daughters must be grounded by the numerical distinctness of the potentially existing packets of prime matter associated with each daughter at each moment of her potential existence.
 
Now, each of these potentially existing daughters is potentially a human being. This modal fact about the twins must be grounded in the potential existence of two substantial forms of the human species. Thus, there must be potential substantial forms as well as actual ones. What is the difference between the two sorts of forms? The actual forms transmit actual existence to their substances, while merely potential forms do not. Hence, there must be acts of existence (actus essendi) which are present in the one case and absent in the other. Thus, we get a real distinction between essence (form + matter) and existence (acts of esse).
 
Those (like Averroës) who reject the real distinction must suppose that every form is an actual form, a source of actual existence. This means that they must deny that merely potential beings are in any sense real. In particular, they must deny that there are potentially existing twin daughters (as described above). They must say, instead, that there could have been such daughters. However, they cannot provide any ground or truthmaker for such a modal truth.