From Necessary Being to God: Why the Gap Problem Doesn’t Exist for Classical Theists

Why a Purely Actual Being, for Aquinas, Cannot Be Anything but God

For the classical theist—specifically Thomas Aquinas—there is no “gap problem.” But what is the gap problem, you ask? In contemporary literature on cosmological arguments, the gap problem is essentially this: why should we call whatever is concluded by a cosmological argument (say, a necessary being) God?

Put differently, cosmological arguments are often presented in two stages by theists. The first stage aims to establish some sort of entity categorically different from entities requiring extrinsic explanation—such as a necessary being to explain the existence of all contingent beings. The second stage is to establish that this categorically different entity is divine, which is where much of the conversation has stalled.¹

So that’s the gap problem—i.e., while it may be interesting to infer the existence of a necessary being, that alone does not prove the existence of God. And yet I’ve just claimed that this issue doesn’t exist for many classical theists, particularly Aquinas. Why? Because Aquinas’s cosmological arguments lead to the conclusion of a being whose essence just is its existence and is purely actual. Through conceptual analysis, the divine attributes—all of them, in their fullest conception—naturally follow from such a being. Aquinas himself devotes considerable attention to this topic; in fact, in his Summa Theologica, he spends far more time unpacking the nature and attributes of God than “proving” God’s existence. While the Five Ways take up only a few brief paragraphs (ST I, Q.2, Art.3), his detailed discussion of divine attributes spans entire sections: simplicity (Q.3), eternity (Q.10), immutability (Q.9), omnipotence (Q.25), and perfect goodness (Q.6). For Aquinas, once the existence of a purely actual being is established, the complete suite of divine attributes logically unfolds—a sharp contrast to approaches that stop at a generic “first cause” or “necessary being” without examining the full implications of its nature, perhaps due to a lack of a robust metaphysical framework that would make such an investigation feasible.

I take this to be a significant advantage of traditional cosmological argumentation—obviously. And the reason why this rigorous unpacking is possible, is precisely because these arguments operate from within a rather heavily loaded metaphysical system. In other words, such arguments, especially those given by Aquinas, are system-dependent—they are staged within a particular metaphysical program that already includes commitments about the nature of causality, contingent objects, goodness, knowledge, and so on. The upshot of this is that once a cosmological argument is run these commitments automatically kick out the divine attributes once a necessary being—for Aquinas, a being whose essence just is its existence, and is purely actual—is reached.

Ironically, however, a common objection to traditional cosmological reasoning—particularly of the Thomistic sort—is this: Aquinas’s arguments may work well, but only if one accepts his metaphysical framework, which is, cue spooky voice, highly controversial. For example, Aquinas is committed to existence being a real, first-level property of concrete individuals, distinct from their essence, and he maintains that entities actually have real essences. And so on.

While these commitments are indeed controversial (but what isn’t in philosophy?), I have three responses to this concern. First, as I’m already suggesting, there are significant advantages to this “metaphysical front-loading” (bridging the gap problem is just one of them). Second, much can be said in favor of this system independently of concerns related to the philosophy of God. Third, anyone wishing to bridge the gap problem will, at some point, also need to engage in serious metaphysics, inevitably adopting their own set of—ahem, back to spooky voice—controversial positions. In other words, no one escapes this; at best, they only delay it.

Here’s another advantage to Aquinas’s approach—the metaphysical commitments that help bridge the so-called gap problem aren’t introduced simply to fill a gap with suspiciously convenient solutions. No, these commitments are already in place for various independent reasons, largely due to their necessity in making sense of broad-scale features of reality—like the occurrence of change (hence the act-potency distinction) or addressing the problem of the one and the many (hence the form-matter distinction on one level and the essence-existence distinction on another). It just so happens that these commitments do significant work in the philosophy of God as well—which, I think, is an ideal outcome because it doesn’t appear contrived. Because it isn’t contrived! In other words, Aquinas isn’t just adopting metaphysical positions that yield the results he, as a theist, wants in the philosophy of God; rather, the commitments he has already established naturally produce those results.

As I will show, if one approaches cosmological reasoning with these Aristotelian-Thomistic commitments—not even all of Aquinas’s metaphysical commitments, which are admittedly extensive, but simply his broadest and (I believe) most defensible ones—and runs an argument like his, the gap problem simply doesn’t arise. The only sort of being that could be truly necessary would also necessarily be one, omnipotent, omniscient, perfectly good, and so on.

But first, here’s a simple and informal sketch of Aquinas’s argument for God, based on his De Ente et Essentia—just the bare rudiments, really. For Aquinas, familiar everyday contingent objects are metaphysical composites of two elements: essence (or “what-ness”) and existence (or “is-ness”), and these elements, though inseparable, are really distinct. The essence of such beings does not “guarantee” their existence. Aquinas, therefore, sees the need to identify a cause for such entities—something that ultimately imparts existence to them. This causal relationship, which Aquinas describes as a “deep dependence” or metaphysical grounding, signals a particular type of causal series. For Aquinas, this series is necessarily terminating; it is what Thomists call a per se, or essentially ordered, causal series. Furthermore, Aquinas argues that if something possesses a property only by participation (in this case, existence), an adequate explanation requires tracing back to something that possesses that property or perfection (or the power to produce it) per se, or by virtue of its own nature.² For Aquinas, this implies that if things have existence only by participation—that is, by being caused to exist—then we must ultimately reach something (at least one thing) that has existence in virtue of what it is.³

Again, much in this line of argumentation needs to be defended (or clarified)—but I’m not going to do that here (I’ve covered it in other places, including my book; I also commend Kerr’s book). My purpose here is simply to show that if one accepts this argument, the gap problem does not apply.

So, let us assume Aquinas’s argument, within his system, successfully leads to the conclusion of a being whose essence just is its existence—granting this conclusion solely to explore the resources Thomas’s metaphysic brings to the gap problem.

I think the best approach is to highlight these resources by examining each of the divine attributes Aquinas believes can be established through a conceptual analysis of a being whose essence is its existence, along with the specific metaphysical commitments that enable these inferences.

We will proceed through the divine attributes in a particular order—offering just a brief sketch and general idea of how each attribute is derived (for the full development, one should turn to Aquinas himself). The logic of this order should become clear as we see how understanding one attribute sets the stage for deducing the next (for instance, how the attribute of being purely actual necessitates being immaterial).

Simple and Self-Subsistent (Uncaused)

For Aquinas, a being whose essence is identical to its existence would be “existence alone” or subsistent existence, as it would not actualize through anything distinct from itself. (Aquinas sometimes refers to this entity as pure existence or pure esse.) Rather, pure existence would be actual by virtue of what it is, precisely because its essence is nothing other than to be. Thus, pure esse would be self-actual and uncaused. Furthermore, as something whose essence is its existence, this entity would not differ from its "to be"; it would be pure (unqualified, uncomposed) being. In short, if anything existed whose essence was its existence, it would be altogether simple and self-subsistent.

In the background, recall that Aquinas holds to an act-potency division of being—one of his core metaphysical commitments, inherited and developed from Aristotle. Every familiar contingent object’s essence relates as potency to its act of existence—because to be a real being, as opposed to merely possible, is to have an act of existence. Essence, then, is the potency side of the equation, and existence is the actuality side. Thus, in a being whose essence just is its existence, the potency side is, as it were, “pushed out,” leaving us with a being that is purely and fully actual—that exists in the most robust sense possible, that is, necessarily, by virtue of what it is. Thus, we have not only reached the result of a necessary being, but a truly ontologically independent being that is necessary through itself. This, I suggest, is a great result because it helps to explain how a being could be necessary in the first place—Aquinas’s answer is because its essence just is its existence.

Pure actuality also entails absolute ontological simplicity, since all other forms of metaphysical composition—such as substance and accident (attribute) or form and matter—relate as potency to act. Therefore, a being that is purely and fully actual will have no composition, either physical or metaphysical. It will be wholly incomposite.⁴

Unique

Once we grasp the notion of subsistent existence, we can see why the only available forms of multiplication (Aquinas adheres to the traditional scheme of genus and species—which, perhaps foolishly, I’ll assume the reader is already familiar with) cannot apply to existence alone, ruling out the possibility of duplication—that is, of there being more than one such entity. Simply put, multiplication would contradict the simple, subsistent nature of existence itself. For instance, if pure existence were multiplied as a genus through the addition of specific differences, it would no longer be simple or pure existence but rather existence plus some specifying form. In other words, pure esse would cease to be pure esse and instead become a restricted or configured esse—esse plus some particular form. This would contradict its nature as simple being.

Alternatively, if pure existence were multiplied through matter, it would no longer be subsistent existence but material existence (and thus an ontological complex). It would exist not in itself but within some distinct packet of matter, becoming a composite of form and matter—no longer simple or self-subsistent. This, too, is inconsistent with what it means to be existence alone. Therefore, neither option is metaphysically tenable.⁵

If this being is God—which we are currently working out—then it follows that there isn’t just happenstance in there being one God; rather, there can only be one God.⁶

Immutable, Immaterial, and Eternal

Change is the progressive actualization of potential. Since God is purely actual, he is therefore immutable—God does not change.

That God is immaterial follows from his lack of composition, as all material beings are composite by having spatially extended parts, and from his immutability, as all material beings are subject to change. God's eternity also follows from his lack of composition (since things moving through time acquire new phases, or parts, of life) and from his immutability (if time is the measure of change, which is the standard Aristotelian analysis, and God is unchanging, then God is not in time).

By eternal, we don’t simply mean that God is everlasting—something could be everlasting within time. Rather, we mean that God dwells in the literal "eternal now," where all temporal reality is available to him and known by him simultaneously. God is timeless, existing entirely outside the spatio-temporal dimension.

Omnipotent

This one is straightforward. If there can only be one entity whose essence is its existence, then everything else that exists is ultimately caused to exist by this one entity. In other words, anything that is possible is only possible insofar as it can receive existence from subsistent existence, and anything that is actual is actual only insofar as it is actually receiving existence from subsistent existence. Therefore, subsistent existence is that which can bring about any possibility of being—a traditional understanding of omnipotence.

Notice that this understanding of omnipotence pertains to production; it does not suggest that God can (broadly) “do” anything, like swim in a lake of cheese. This understanding of omnipotence—which, like all the other divine attributes Aquinas deduces, is derived a posteriori through effect-to-cause reasoning—is restricted in a principled way, avoiding certain paradoxes that plague less restricted versions.

Omniscient

Omniscience is a bit trickier, but only because we first need to unpack Aquinas’s theory of knowledge, which involves the possession of form. Here’s the short version (again, please keep in mind that my aim is not to defend these commitments, but to show how they help resolve the gap problem): For Aquinas, to be intelligent—or indeed, to be a knower—is to possess the form of something within oneself without actually becoming that thing. For example, a block of marble does not receive the form of a statue without actually becoming a statue; this is “material” containment, the way form is contained in matter. However, we, as intelligent agents, can possess the form of a statue without becoming a statue, and we do this by understanding the form—what Aquinas calls “intentional” containment, or the way that form exists within form.

Now, since God is pure existence itself, God possesses every possible form of existence, as any form is simply some mode of existence. However, given God’s simplicity, God cannot be identical to any particular form; instead, God must possess these forms intentionally, or in an intelligent manner. The link to God’s omniscience—God’s knowledge of everything about the actual world, not just himself—arises from a combination of God’s perfect self-knowledge (perfect self-possession of his own form, to which he is identical) and God’s executive knowledge—God’s awareness of what he is doing when causally bringing about the world. Put differently, God knows everything that is happening in the world because God knows himself perfectly, which includes knowing what he is bringing about.

Because God is purely actual, none of his knowledge can be passive or imparted to him. This fits well with God’s universal causality— God’s knowledge is active, executive, perhaps even entirely tacit, we might say. God knows what is happening in the world precisely because he is causing it to be.

Perfectly Good

Perfect goodness, like omniscience, requires introducing another key element of Aquinas’s metaphysical system: his theory of the transcendentals and, specifically, the convertibility of goodness and being. In short, goodness is not something additional to being but is being itself, considered under the aspect of perfection or desirability. Thus, being and goodness (as well as truth) are convertible—distinct in meaning but identical in reference. As Gaven Kerr explains:

“Like truth, goodness does not add anything to being, but designates a relation. Whereas truth signifies the relation of being to an intellect, goodness signifies the relation of being to the will. In other words, the goodness of being is being considered as desirable, aligning with the traditional Aristotelian definition of the good as that which all desire.”⁷

Kerr further clarifies:

“Something is perfect when it is complete in itself. Accordingly, when something is lacking in some respect, it is perfected (in that respect) when it receives what it lacks. When such a thing receives what it lacks and is thereby perfected, what it received is good for it. To say that a thing is perfected is to say that it is actualized in a certain respect. Now, nothing is actual unless it exists, and nothing exists unless it has esse. . . . Esse is the principle of being, without which there is nothing; and since esse is the perfection of all perfections, all being is good. Therefore, wherever being is found, goodness is found, with goodness representing the desirability of being.”⁸

With this background, we can see why God’s goodness follows from God’s being purely actual—pure existence, or pure esse, as Aquinas terms it. Since being and goodness are convertible, God, by virtue of being pure being, is also pure goodness. Because there are no unactualized potentials in God, there is no higher or further perfection for God to attain.

Furthermore, because God is qualitatively infinite and unrestricted, his perfection is absolute, unlike the relative perfection attainable by beings with restricted essences.⁹

Conclusion

With Aquinas’s metaphysical commitments in place—the act-potency distinction, form-matter and essence-existence distinctions, the theory of transcendentals, knowledge as possession of form, and so on—commitments which, I believe, are extremely theoretically fruitful even apart from considerations of God—the gap problem resolves. In fact, it’s fair to say that there really is no gap problem at all for Aquinas. Within the Aristotelian-Thomistic system, a being of pure actuality simply could not be anything other than what everyone would recognize as God (“… and this everyone understands to be God”).

Now, not everyone may accept these commitments; fair enough—that’s a different conversation. But I maintain that there’s no way to fully bridge the gap without adopting serious metaphysical commitments along the way, which will be no less controversial (or plausible, for that matter) than those held by Aquinas. In fact, many may find themselves needing commitments very similar to Aquinas’s—or near enough—to make a compelling case for full-throated divinity based on, say, necessity alone. And maybe that’s precisely why the gap problem has become so prominent in recent years; whether the gap can be bridged really depends on broader metaphysical considerations that aren’t so quickly or easily settled. My only suggestion here is this: if you see the sense in this, then there’s good reason (yet again) to turn your attention in Aquinas’s direction.

- Pat

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1. Of course, several strategies have been proposed by theists to bridge or address this gap. Some are deductive, while others are abductive, using inference to the best (and simplest) explanation. Some approaches are partial, aiming to establish only a few divine attributes or attributes that resemble divinity (e.g., immateriality, immense power), while others argue for the full traditional triad: omnipotence, omniscience, and perfect goodness. One might think that reaching one or two divine-like attributes is sufficient, but this isn’t quite right, especially given that theism and reductive naturalism aren’t the only metaphysical options available.

There are, for instance, versions of "limited theism" (for lack of a better term), which affirm the existence of a god-like being with specific, though circumscribed, attributes such as power—Philip Goff endorses a view along these lines. There is also, though often presented as a parody, the "evil god hypothesis," which posits a being that is extremely powerful and all-knowing, but perfectly malevolent. Thus, while establishing one or two divine-like attributes is consequential for certain naturalistic views, it leaves other metaphysical options very much alive and competitive. I take it that theists would prefer an approach that rules out these alternatives as well, which is exactly what Aquinas’s approach does, as we’ll see.

2. It’s worth noting that Aquinas is not making the obviously simplistic error of assuming that whatever actualizes a potency must itself be identical to what it brings about. For instance, it’s clearly false to think that only a chair could cause something else to become a chair, even if it’s true in many cases that things often produce their likeness (e.g., fire producing fire). Rather, Aquinas’s point is modest: whatever introduces actuality into something must itself be actual and capable of bringing about that actuality. In short, whatever produces F must have an F-ness-producing power, which requires it to be actual, as no merely potential thing can actually do anything. For a defense, see Gaven Kerr, Collected Articles on the Existence of God (Germany: Editiones Scholasticae, 2023), 159. As Kerr points out, “Aquinas offers an account of how perfections present in effects can pre-exist in their cause in a non-univocal, but virtual, sense and so causes, whilst not in act in the same way as their effects, are sufficiently in act to produce their effect.” Furthermore, something might not have an F-ness-producing power on its own but only in conjunction with other contributing causes. Ibid., 166.

3. I take it that Aquinas is generally committed to a restricted version of the Principle of Sufficient Reason (PSR). In fact, he explicitly endorses a causal principle that could be seen as a restricted version of the PSR: “Whatever belongs to a thing belongs to it either as a result of its intrinsic nature or as the result of some extrinsic principle.” (See Gaven Kerr, Aquinas’s Way to God [Oxford: Oxford University Press, 2015], 91, for Kerr's articulation of Aquinas's causal principle as featured in De Ente et Essentia.). On the other hand, Patrick Flynn—often described as a devilishly handsome Maverick philosophy, with beastly muscles—presents a Thomistic argument that does not require PSR. [Forthcoming Nova et Vetera]

4. How all this fits with the doctrine of the Trinity, which Aquinas obviously affirms, is a notoriously complex issue and definitely not something I plan to address here. For a thorough—and, I think, ultimately satisfying—treatment, see Lonergan’s Systematics.

5. Fortunately, this argument does not rely on the Identity of Indiscernibles (IOI). The argument simply contends that, given the nature of multiplication, something whose essence just is its existence could not be multiplied. This claim doesn’t require us to assert that if there were multiple "pure existences," they would be identical due to being indiscernible. Therefore, any controversy surrounding IOI does not impact the multiplicity argument.

We can reinforce this point. Suppose there could be something whose essence just is its existence—something ontologically simple. If there are two instances of such a being, there must be some difference between them. Even if we assume IOI is false, so that these qualities or properties might be indistinguishable, there would still be a difference between the two instances. Should anyone contest this (utterly obvious) point, I would insist—with a thundering foot stomp, if necessary—that it is, after all, essential to an individual that it be different from others, even if it is not essential that we can specify in what that difference consists.

Either way, this difference implies that any similarity between the instances would be expressible in terms of qualities or properties as ontologically grounded entities, which contradicts the ontological simplicity of pure existence. Therefore, pure existence must be restricted to one instance, if it exists at all.

6. Here’s another (reinforcing) way to make the point, one that gets to the heart of the matter. For Aquinas, anything identical to its existence must be ontologically simple. Now, suppose there are two distinct instances of something whose essence is identical to its existence. Since they both exist subsistently, they share at least that feature in common. However, because these entities are truly distinct from each other, each must possess at least one feature or property that the other lacks (even trivially so; discernibility is irrelevant). But whatever that distinguishing feature is, it must be compounded with the feature they share, which contradicts the simple nature of subsistent existence.

7. See Kerr, Gaven. “Goodness and Being, Transcendentals, and Participation.” In The New Cambridge Companion to Aquinas, edited by Eleanor Stump and Thomas Joseph White, 192–210. Cambridge: Cambridge University Press, 2022.

8. Ibid.

9. It’s important to clarify that we are not saying God is perfectly good in the sense of being a supremely virtuous person—a human “moral exemplar” like Mother Teresa. God, apart from the Incarnation, is not human, does not possess a human essence, and thus does not possess acquired virtues, vices, or even moral obligations, as these would imply complexity. This is not to say that God could do evil or sin. Sin is ultimately a falling short of full actuality, and since God is fully actual, sin is impossible for him, metaphysically speaking. Sin signifies a privation or imperfection, which God, as the most perfect being, lacks entirely.

In sum, we are saying that God, whatever else he is, is the most perfect of beings. And the kind of being God is—the most perfect being possible—may not align directly with our typical understanding of moral goodness as it applies to human beings. This is why various formulations of the problem of evil, which assume moral obligations relevant to human beings for their perfection, are operating under something of a category mistake, as Fr. Brian Davies has routinely pointed out.