St. Thomas Aquinas on God as Ipsum Esse Subsistens

Abstract

St. Thomas Aquinas’s doctrine of God as ipsum esse subsistens is not easy to understand. Even some of his more informed interpreters appear to struggle with it. In this paper, I attempt to explain the doctrine in a way that I hope is intelligible to a fairly broad philosophical audience. I also respond to Norman Kretzmann’s interpretation of it, which I think is mistaken. The main problem with Kretzmann’s interpretation seems to be a failure to grasp what Thomas means by esse.

The doctrine of God as ipsum esse subsistens or “subsistent being itself” would seem to be of central importance for St. Thomas Aquinas. And yet, even some of Thomas’s more informed interpreters appear to struggle with it. Norman Kretzmann and Sir Anthony Kenny come to mind in this regard. Whereas, for Kretzmann, the doctrine proposes a being incapable of existing (Kretzmann 1997, p. 127), for Kenny, it is simply “nonsense” (Kenny 2002, p. 110). But as insightful as Kretzmann and Kenny might be about other points of Thomas’s thought, I am not persuaded that either has well understood this one. Kenny’s interpretation has already been ably addressed by several critics, so there is no need for me to discuss it again here (see, for example, Klima 2004; Long 2005; Kerr 2015, pp. 156–62; Ventimiglia 2018). But I am not aware of any response to Kretzmann, and I believe that one is called for given his credentials as an interpreter of Thomas. That, then, is what I propose to do here. In the first few sections of the paper, I will set out Thomas’s doctrine as I understand it, first examining its main terms, taking each in turn, and then moving on to the reasoning by which he supports the application of ipsum esse subsistens to God. The elucidation of esse will be especially crucial since it is on this particular point that Kretzmann seems to go wrong (as does Kenny). Having set out Thomas’s doctrine in its basic form, I will then address Kretzmann’s missteps. In doing that, I will also spend time going over another interpretation, namely, Christopher Hughes’s, since Kretzmann accepts certain arguments made by Hughes. Indeed, it is probably more precise to refer to Kretzmann’s interpretation of Thomas’s doctrine as the Kretzmann–Hughes interpretation, and that is how I will refer to it in what follows.1

1. What Is Esse?

I will begin with esse. As much as I can, I am going to leave esse and its subject, ens (plural = entia), untranslated. Grammatically speaking, esse is the present infinitive of sum (“I am”) and ens is the present participle of esse. If one prefers a very literal rendering, then esse can be translated into English as “to be” and some of Thomas’s translators do just that (see Aquinas 2001), but most translate it either as “being” or “existence”. Ens is standardly translated into English as “being” (which can cause some confusion when esse is also translated as “being”) or “a being” and less standardly as “entity” or “an existent”.

Thomas’s understanding of esse remains pretty consistent throughout his career. For Thomas, esse is, in the first place, an act (actus). Thus, he tells us that “esse is simply said of anything according as it is in act” (unumquodque enim simpliciter esse dicitur secundum quod est in actus) (S. th., I-II, q. 6, a. 6.).2 Moreover, he holds that esse is the most fundamental act of a thing: Esse is that which is innermost in each thing and what is most fundamentally inherent in all things since it is formal in respect to whatever is in a thing (formale respectu omnium quae in re sunt).

(S. th., I, q. 8, a. 1)3

Following Aristotle, Thomas regards form as an immanent principle of act.4 So, when he says here that esse is “formal in respect to whatever is in a thing”, he is indicating that esse is that whereby the entirety of a thing is actualized.5 He uses esse interchangeably with actus essendi (which we could translate as “act of being” or “act of existing”).6

Clearly, if we want to understand esse better, we need to understand what Thomas means by “act”. To do this, it will be useful to consider how act is related to potency (potentia). The two are contrasting principles but they are also positively related insofar as potency qua potency is ordered to act. This is what Thomas has in mind when he says that “something is called a ‘potency’ in relation to an act” (De spirit. creat., a. 11).7 We can think of potency as a capacity for act. An illustration might help us to grasp the point. Suppose that at t₁ Mary is able to run but is not running. In other words, at t₁ Mary knows how to run and has the requisite physical dispositions but, for whatever reason, is not doing so. And then suppose that at t₂ Mary does run. Thomas would tell us that at t₁ running is a potency in Mary and that at t₂ it is an act.

Applying this to esse, we can say that, for Thomas, esse is that act by which any ens that is possible—a potency—is made actual. It is the very act that constitutes an ens as an ens. I deliberately chose the example of running because Thomas himself suggests an analogy between running/runner and esse/ens:

[J]ust as we can say of he who runs or of the runner that “he runs” because he is the subject of running and participates in it, so we can say that an ens, or that which is (id quod est), “is” because it participates in the actum essendi.

(In De ebdom., l. 2)8

Esse is constitutive of ens not because esse produces ens as an efficient cause. Esse does not stand over against ens as another ens or quasi-ens. It constitutes ens by being, as we saw above, an immanent “formal” cause.9 The running/runner analogy is again helpful here. Running is not something apart from, over against, runners, but the immanent act that constitutes them as runners.

The disanalogy between running and esse should also be noted. Running is what Thomas would call an “operation” (operatio)—a particular act flowing from a particular power of an ens that presupposes that the ens as a whole is already in act through esse. Esse is not an operation of an already constituted ens but, again, the act by which the ens as a whole is constituted as an ens.10 Without esse, Mary cannot run or perform any other operation. Every operation she does presupposes the constitutional act by which she is an ens.11

Esse, as we should now see, is not just another principle alongside others; it is absolutely decisive. If esse is what constitutes an ens as an ens, then without esse, there would be no ens, that is, there would be nothing at all. Hence, esse would be the Thomistic answer to Leibniz’s famous question “Why is there something rather than nothing?”12 Esse is the reason why there is anything at all.

Thomas sometimes says that esse can be compared to essence (essentia) as act to potency (See S. th., I, q. 3, a. 4; Q. d. de anima, a. 6).13 The essence of an ens is what it is. Thomas also calls this “quiddity” (quiditas) and “nature” (natura) (De ente, c. 1).14 Thus, the essence of Mary is “human being” or, as Thomas would also say, “rational animal”. How does this act/potency relationship between esse and essence line up with the act/potency relationship between esse and ens? If we consider an essence in itself, in abstraction from some particular existing ens to which it belongs, then essence is just a possible way that esse can be instantiated, that is, it is a possible ens. An essence is possible vis-à-vis esse insofar as there is nothing contradictory about it, for a thing is possible to the extent that it does not imply a contradiction (See S. th., I, q. 25, a. 3).15 If there is no contradiction in “rational animal” or some other essence, say, “limestone”, considered, in itself, then particular rational animals and chunks of limestone—these entia—can exist, as indeed they do.

For Thomas, in all cases save one (that is, in the strange case of God, as we will see later) there is, as later Thomists will say, a “real distinction” (distinctio realis) between esse and essence. What is meant by this is that the distinction between them is not simply a mental (or logical) one made by us, but one that actually obtains in the ens itself.16 If the distinction were merely a mental one, then, in reality, Mary would not be a rational animal and this chunk of limestone would not be limestone; both would just be esse. But, of course, that is not the case. Esse is something that Mary and the chunk of limestone both certainly have, and, therefore, they exist, but esse is not what they are.17 Despite the reality of the distinction between esse and essence, the latter cannot occur without the former, for without esse it would be nothing.

Now, according to Thomas, esse is mediated in entia by their essence (See De ver., q. 27, a. 1, ad 3).18 What this means is that (except, again, in the case of God) the essence “contracts” or “limits” esse to this or that kind of thing.19 Thus, Mary has esse—exists—as a rational animal (and not as, say, a tree) and this chunk of limestone has esse—exists—as limestone (and not as, say, a horse). Another way to put this, following the language of Domingo Báñez, is to say that essence “specifies” (specificat) the way that some ens has esse (Báñez, p. 141). Thomas is saying the same thing when he tells us that “the nature or quiddity of the genus or the species determines the existing” of an ens (In I Sent., d. 23, q. 1, a. 1, ad 2).20

Because esse considered in itself is simply act and, thus, wholly devoid of potency, Thomas also thinks of it as pure perfection. Things are imperfect insofar as they have unrealized potencies. Consequently, whatever lacks potency and is pure act, will also be pure perfection. This is why Thomas says in De potentia, q. 7, a. 2, ad 9 that esse is “the actuality of all acts and, because of this, the perfection of all perfections”.21 Esse, as such, therefore contains all perfection. While we may be able to distinguish esse from this or that perfection conceptually, esse will still really contain all perfections. Of course, any ens that by its essence limits esse and is not pure esse will not itself be pure perfection and contain all perfection but will be a kind of limited perfection. It is for this reason that Báñez says that essence “diminishes” (deprimit) and “imperfects” (imperficit) esse (Báñez, p. 141). As we will see later, Hughes refers to essence in this respect as a “filter” of esse. I suppose that this is also an acceptable way of putting it.

Thomas, again following Aristotle, divides entia into two classes: substance and accidents. A substance, says Thomas, “is an ens through itself” whereas an accident “is an ens through another and in another” (In I Peri., I, l. 8, n. 6).22 There cannot be “running” or other attributes—say, “puzzled”, “holding an umbrella”, “musical”—without a subject of the attributes—Mary, for example. This is not merely a grammatical point but an ontological one. Thomas regards substances as the subjects in reality that underlie various attributes.23 Thus, he tells us that one meaning of substance—derived from the root of its literal meaning—is to “stand under” (substare) (In I Sent., d. 23, q. 1, a. 1).24 Substances are entia of or through themselves (per seipsam) precisely because they are the ultimate “support” of attributes and are not—as accidents are—entia that only exist as attributes of other things.25 This is not to say that substances cannot depend upon other things for their esse. They can depend upon other things (Mary, for instance, requires oxygen to exist), but they depend upon them not as mere attributes of those things.26 Attributes of the sort that accidents are, can never exist on their own apart from other things whereas substances are such that they can exist on their own apart from at least some other things, which tells us that substances have a certain completeness in themselves. Accidents, on the other hand, are radically incomplete in themselves.27 The one exception to this division of entia by substance and accidents, as we will see in a moment, is God.

From what I have said about esse and ens in this section of the paper, it should be clear to us that there is both similarity and difference across different instances of esse and ens. The similarity consists in this, that in every case esse is an act and ens is the subject of that act. The difference is that this act and its subject will take on different “shapes”, if I may so put it, in different cases. Esse is realized differently in substances and accidents and so they are not entia in the exact same way. Moreover, esse is realized differently in different kinds of substances and different kinds of accidents, constituting different kinds of entia both among the former and among the latter.28 Thomas recognizes these similarities and differences and tells us that esse and ens are analogical (De pot., q. 7, a. 7).29 Consequently, when we predicate esse and ens of substances and accidents we predicate them analogically and we likewise predicate them analogically of different kinds of substances and different kinds of accidents.

2. Pure Esse

Only a few words need to be said about ipsum. According to my translation of it at the beginning of the paper, the ipsum in ipsum esse subsistens means “itself”. It is an emphatic pronoun and, in this context, it is intended to express that we are not dealing with esse of just one kind or another but with esse itself, esse in its total purity (De ente, c. IV).30 To say that x is ipsum esse is to say that it is esse and nothing else. But recall that this would not mean that x could not possess perfections that are conceptually distinct from esse since esse as such contains all perfections.

3. Esse and Subsistence

More needs to be said about subsistens—or “subsistence”—than I have said about ipsum but not much more. Here is one of Thomas’s explanations of subsistence in his Scriptum on the Sentences of Peter Lombard:

Subsisting can mean two things, namely, existing (esse) and existing in a determinate way (determinatum modum essendi); and to exist simply speaking only pertains to individuals, but existing in a determinate way is from the nature or quiddity of the genus or the species [of the ens].

(I, d. 23, q. 1, a. 1, ad 2)31

So, subsistence is always about esse. To say that x subsists is to say either that x exists simpliciter or that x exists in this or that way as determined by its essence. What Thomas leaves out of this explanation (although perhaps it is implied) but mentions later in the same article in the Scriptum is that subsistence is always an esse per se. What subsists exists of or through itself either to some extent or absolutely:

But “subsisting” is said of something inasmuch as it is under (sub) its own esse, not because it has esse in something else as in a subject.

(I, d. 23, q. 1, a. 1, ad 3)32

In other words, subsistence could never apply to accidents since they never exist on their own apart from other things.33 But substances, of course, subsist. Thomas says that it is proper (proprium) to them to do so (See Cont. gent., IV, c. 66).34 Still, Thomas also holds that God subsists but he denies that God belongs to the genus of substance as an individual substance. He only “belongs” to it as its principle.35 Consequently, we can say that there is an important sense in which, for Thomas, God is not a substance. If that is his view, then subsistence is not something exclusive to substances and when Thomas asserts that God subsists, we should not assume that this means that God is a substance.36

4. Getting to God as Ipsum Esse Subsistens

We should now have some understanding of what it means, for Thomas, to claim that God is ipsum esse subsistens. But by what reasoning does he justify this claim? There are different approaches that Thomas takes to arrive at the proposition. I want first to look at the approach that he takes in the prima pars of the Summa theologiae.

In q. 44, a. 1, Thomas argues that “everything that in any way is, is from God”.37 More specifically, he argues that everything that is, apart from God, has its esse caused by God as ipsum esse subsistens. What Thomas is talking about here is creation (creatio). By “creation” he means producing the esse of an ens from nothing (See S. th., I, q. 45, aa. 1 and 6).38 Thomas does not try to show in this article what justification there is for understanding God as ipsum esse subsistens because “this was shown (ostensum est)”, he tells us, “where we dealt with divine simplicity”.39 And yet, when we turn to q. 3 on divine simplicity, we do not find the term ipsum esse subsistens in any of the eight articles. However, once we read q. 3 carefully, it becomes clear that what is unsaid is, nevertheless, implied. A key attribute of ipsum esse subsistens in q. 44, a. 1 is that, unlike everything else that receives esse from it, esse belongs to the essence of ipsum esse subsistens. Thomas establishes that esse belongs to God’s essence in q. 3, a. 4.

Before looking at that article, however, I want to run through what Thomas does in the previous article. Doing that will make it clearer what Thomas takes himself to be entitled to conclude in q. 3, a. 4. In q. 3, a. 3, he shows us that God is identical with his essence. Entia such as we are, namely, material substances, are not identical with their essences. We know this because we are each a particular instance of an essence and, therefore, have a determinateness that is not included in our essence. As Thomas points out, “this flesh, these bones, and the accidents that designate this matter are not included in humanity”.40 If they were included in humanity, then by virtue of being human, we would all be numerically the same person, which we obviously are not. From a little reflection, we see that the same will hold for all other material substances—animals, plants, minerals, etc. Every material substance will be a particular thing with particular features that are not included in its essence. So, no material substance will be identical with its essence. But God is not a material substance. He cannot be because matter is a principle of potency and God, as the first unmoved mover (a divine attribute that Thomas concludes to in the first of the Five Ways in q. 2, a. 341), must be pure act. If there is no matter in God, then there will be nothing by which he is distinguished from his essence. Consequently, he must be identical with it.

In q. 3, a. 4, Thomas offers three arguments for his claim that esse belongs to God’s essence.42 In the first argument, he uses a premise that he proves in q. 2, a. 3, namely, that God is the first efficient cause of everything that exists apart from himself.43 If this is so, then God himself cannot receive his esse from another, for there would be no other ens that exists apart from God from which God could receive his esse. So, esse must belong to his essence. In the second argument, Thomas notes that if God’s esse were something other than his essence, then his essence would be a potency actualized by his esse. But since God is pure act, he explains, there can be no potency in him. Thus, again, his esse must belong to his essence. Finally, in his third argument, Thomas points out that if esse does not belong to God’s essence and he must receive it from another, then he would not be the “first being” (primum ens), which, he comments, would be “an absurd thing to say”. It would be absurd, that is, in light of the Five Ways that lead us to God as the first being.

It is important to remember that, in Thomas’s view, there is nothing outside esse. If this is so, then there can be nothing that can be added to it. Thus, if God’s essence is esse, then there is nothing else that it could be but esse or, positively stated, it will be pure esse—and all the perfections that esse contains—or ipsum esse (because, as I said earlier, to say that something is pure esse is to say that it is ipsum esse).44 This makes God radically different from every other ens. No other ens is esse. All other entia have esse but none is esse.

Do q. 3, aa. 3 and 4 allow us to conclude that God as ipsum esse is also subsistens? They do. If God as God is ipsum esse, then he does not need to and could not receive esse from anything outside of him. Moreover, if there is nothing outside of esse and God is pure esse, then there is nothing at all about God that could come from anything outside of him. Hence, nothing could exist more independently and, thus, be more subsistent than God.

Kretzmann takes up Thomas’s doctrine of God as ipsum esse subsistens in commenting on Summa contra gentiles, I, c. 22. So, I would like to take a look at that text too. In c. 21, Thomas had argued that God must be identical with his essence and in c. 22 he argues that God’s essence and esse must be identical. Thus, in the conclusions they come to cc. 21–22 parallel Summa theologiae, I, q. 3, aa. 3–4.

Thomas offers six arguments for the identity of God’s essence and esse in c. 22, but Kretzmann only attends to the first and my purposes here do not require that I do otherwise. Thomas begins the first argument by noting that he has shown in a previous chapter that there is an esse that necessarily is esse through itself and that this is God.45 As Kretzmann explains, Thomas had concluded this in c. 15.46 Thomas then goes on to say that if this esse is not identical with its essence, then either it is incompatible with its essence or it is not. The first horn of the dilemma is obviously not an option, for nothing can be incompatible with what it is. That would mean that it cannot be what it is, which violates the principle of identity and is, thus, impossible and nonsensical. That leaves us with the second horn. If the esse in question is compatible with its essence but other than it, then, says Thomas, we are faced with the following trilemma: either the esse will depend upon its essence, or both the esse and the essence will depend upon some other cause, or the essence will depend upon the esse. We can dismiss the first two possibilities because the esse we are concerned with has already been shown to be necessary and, therefore, cannot be dependent on anything else. We can also dismiss the third possibility because if the essence depends on the esse, it would be an accident and not the essence of the esse. If none of the alternatives that are entailed by the hypothesis of the non-identity of this esse and its essence are acceptable, then, reasons Thomas, we have to grant that this esse, which is God, is identical with its essence.

If the identity of esse and essence in God logically entails that God is ipsum esse subsistens, as we saw in our look at q. 3, a. 4, then what Thomas argues in c. 22 will also entail this.

We saw in the second section of the paper that esse and ens are predicated analogically of different entia. We can now see that they will be predicated analogically of God and all other entia in a special way. God’s esse is more different from the esse of creatures than the esse of any creature is different from the esse of any other creature. Of no creature, for example, is it true that it is esse, but this is true of God. If God is esse, then one might wonder whether it even makes sense to speak of God as an ens. Thomas definitely thinks that it does because he is always referring to God as an ens. To say that something is an ens is simply to say that esse belongs to it, and this is preeminently true of God. All the same, we must recognize that God is an ens sans pareil.47

At the beginning of the paper, I suggested that the doctrine of God as ipsum esse subsistens is of central importance for Thomas. We should be in a position at this point to appreciate one respect in which this is the case. Earlier, I said that esse is the reason why there is anything at all. This is true, but we are now able to be more precise. The esse of entia apart from God is the immanent and proximate reason for everything apart from God. But God as ipsum esse subsistens is the transcendent and ultimate reason for everything apart from him since everything apart from him receives its esse from him. Without ipsum esse subsistens there is nothing. Nothing else would have what is required to be the ground of everything. I think that it is for this reason that Serge-Thomas Bonino tells us that God as ipsum esse subsistens is, for Thomas, “the key to all metaphysics” (Bonino 2016, p. 271).48

One last point that it will be worthwhile to consider about Thomas’s doctrine of God as ipsum esse subsistens—as will become clear in the next section—is how it connects with God’s perfection. If God is pure esse, then he must also be pure perfection. This must be so because, as we saw earlier, there is an identity between esse and perfection since in itself esse is pure act and to be wholly in act is to be wholly perfect. This identity is what allows Thomas to claim in Summa theologiae, q. 4, a. 2, ad 3 that “no perfection of esse (perfectionibus essendi) could be lacking in that which is ipsum esse subsistens”.49

5. The Kretzmann–Hughes Interpretation

So, what does Kretzmann have to say about all of this? Here is how he begins his interpretation of Thomas’s doctrine of God as ipsum esse subsistens:

Now it can’t be the case that what explains the existing of everything that exists is itself just another thing that exists, even just something that uniquely exists necessarily through itself. As Aquinas says elsewhere in the chapter … “[The word] ‘existing’ names a kind of actualization (actum quendam), since something is said to exist not because it is potentially but because it is actually”. That is the way “existing” is used, all right, but for just that reason it can’t be quite right to say regarding whatever is at the basis of all existing simply that it exists. That standard way of talking suggests an instantiated nature, even if it should be a nature that entails its own instantiation.

(Kretzmann 1997, p. 127)

I wonder about the propriety of the translation of the line from Thomas’s text that Kretzmann offers here. The whole phrase in Latin runs like this: Esse actum quendam nominat. Kretzmann’s decision to translate actum as “actualization” can be questioned. A more literal translation would be “act”. To be sure, in some cases of Thomas’s use of the term actus, it could be translated as “actualization”. In c. 22, however, there is no particular reason to do so, and, in fact, I would argue that here it is a mistake to render actus in this way in this text. In English, “actualization” has the connotation of a movement or transition. Understood Thomistically, it would connote the movement from potency to act. “Act”, on the other hand, does not necessarily have this connotation. In this part of c. 22, Thomas obviously means to make a statement about what esse is in general. But, as we should understand from my account of esse earlier in the paper, esse is not, considered in itself, a movement from potency to act. Considered in itself, esse is act, pure and simple. If esse implied potency (as “actualization” does), Thomas would never regard esse as something appropriately predicated of God (unless it is intended metaphorically).

I do not want to press this objection too hard, though. I have no reason to think that Kretzmann would not have conceded the problem with this translation had his attention been drawn to it. And it is not central to my concerns about the Kretzmann–Hughes interpretation. All the same, I think it must be noted. But I find nothing to object to in the rest of what Kretzmann says in the above text.

As Kretzmann continues commenting on c. 22, however, things get worse. Referring to the identity of God’s esse and essence for which Thomas argues in the chapter, he writes:

But exactly which identity is at issue? It may seem more elegant for [God’s] nature to be finally identified simply with being. Aquinas himself sometimes puts the identification that way in these chapters and elsewhere: God, or God’s nature, is “being itself (ipsum esse)”. However, that way of putting it suggests that God is nothing but existence, and, as one recent critic puts it, “nothing subsistent could be just existence: a merely existent substance is too thin to be possible” (Hughes 1989, p. 21). The identification Aquinas seems to prefer is this: God, or God’s nature, is “his own being (suum esse)” that is, the uniquely necessary being of the kind that ultimately explains all existing.

(Kretzmann 1997, pp. 127–28)

Kretzmann makes two claims here pertinent to our question. Let us consider the second one first. According to this claim, Thomas prefers—or seems to prefer—to say that God is his own esse rather than that God is esse itself. How does Kretzmann justify this claim? He adverts to the greater statistical frequency in the Summa contra gentiles of the first expression. He notes that there are at least six times that Thomas says that God is esse itself and at least nine times that he says that God is his own esse (Kretzmann 1997, p. 127, nn. 14, 16). If Kretzmann wants us to believe that Thomas sees a problem with saying that God is esse itself, this argument will hardly do. What he would need to show us is that Thomas himself tells us this or (something less decisive) that Thomas never says that God is esse itself. But Kretzmann cannot show either of these to be the case because neither is true.

Now to the second claim. Kretzmann tells us that nothing subsistent could just be existence. This amounts to saying that ipsum esse cannot be subsistens. In his view, it cannot be the case that Thomas teaches that God is ipsum esse subsistens. Kretzmann does not give us an argument to support this claim but appeals instead to the work of Christopher Hughes. We will need to turn to Hughes, then, to understand what is behind Kretzmann’s objection.

Here is Hughes’s argument:

For Aquinas … there is nothing more to God than His existence. In that case, it looks as though God will just exist, because there will not be anything else in Him over and above His existence, by virtue of which He could be anything over and above existent. Since there will not be anything in God but existence, and the existence of a thing does not make it anything but existent, God will be nothing more than existent. But it seems clear that nothing subsistent could be just existent: a merely existent substance is too thin to be possible. Moreover, even if some substance could be simply existent, God could not be, since He is any number of other ways than just existent—good, wise, and just, as well as omnipotent, omniscient, and the like.

(Hughes 1989, pp. 21–22)

Thomas might balk at the unqualified connection that Hughes makes here between subsistence and substance. If Hughes’s argument were to be put into terms that Thomas would find more acceptable, it would have to drop “substance” and just talk about “subsistence”. But what does Hughes mean by something being “too thin” to be possible? The possibility that he is talking about appears to be subsistence. Hughes must mean that there are things that are “too thin” to subsist in the sense that they could not exist all by themselves without something being added to them. So, the thinness at issue would be a kind of ontological thinness. But how could something that is pure esse (as Thomas understands esse) be too ontologically thin to subsist? What could possibly be added to pure esse to make it capable of subsistence? These are rhetorical questions. As we have already seen, it is the very fact that God is pure esse that makes him radically independent of all other things. Nothing needs to be—nor could be—added to pure esse to make it subsistent. By its nature it just cannot depend upon anything else.

How might Hughes respond to this? That is not entirely clear. The one possibility that I can see (which is not expressly presented as such by Hughes) is showing that pure esse cannot be pure perfection (as we have seen Thomas holds). Hughes argues this later in the text. If God is pure esse and pure esse is pure perfection, then God would necessarily be subsistent because something that is pure perfection lacks nothing that it should have and, therefore, is not in need of anything outside of itself. Hughes already intimates his rejection of this view of pure esse by what he says at the end of the text I have quoted. There, he tells us that if God is pure existence, this would exclude his being good, wise, just, and so on.

So, let us consider the argument that Hughes makes against the identity of pure esse and pure perfection. I take his core claim to be that esse and perfection cannot in any way be identical because perfection admits of degrees whereas esse does not, that is, something can be more or less perfect but esse cannot belong to anything more or less—it either has esse or it does not. This is Hughes in his own words:

If what God has according to its full power is not, say, being white, or being square, vel cetera, but just being, then it would seem that what God has according to its full power is just existence. And if there is any intelligible content to the idea that there is a difference between having existence according to its full power, and having existence according to something less than its full power, I cannot grasp it. […] I think I can understand the difference between having whiteness according to its full power and having whiteness according to something less than its full power, because, I take it, it is the difference between being less than perfectly white and being perfectly white. By contrast, there does not seem to be a difference between being perfectly existent and being less than perfectly existent. Existence is an on/off property: either you’re there or you’re not. Because existence is on/off, it would seem, either you have it according to its full power or you don’t have it [at] all. In short, although Aquinas holds that esse or existence fails to include every perfection only insofar as it is “filtered”, the distinction this presupposes—between having filtered existence, and having “the entire fullness of existence” (DSC I, responsio50)—is on the face of it unintelligible.

(Hughes 1989, p. 27)

Hughes borrows the whiteness example from Thomas. In Summa contra gentiles, I, c. 28, Thomas compares God to whiteness in this way: God, as esse itself, has the full power of esse just as a subsistent whiteness (if there actually were such a thing) would have the full power of whiteness. Thomas concludes from this that God is “totally perfect” (universaliter perfectum).51 We know that Thomas would see this following because he holds that pure esse as pure act must be pure perfection.

Is the idea that there could be degrees of esse, such that A could possess esse more or less fully than B, really unintelligible, as Hughes alleges? He is willing to entertain degrees of whiteness but not degrees of esse. But let us consider what would cause something to be less white than another thing. It would seem that this occurs when something non-white, something that darkens the whiteness, gets mixed in or blended with the white. Suppose I have a can of white paint that I do not alter in any way and another can of white paint to which I add some black paint. Doing that will darken the white. The more of the black that I add the less white the paint will be until it ceases to be recognizable as white. All along the way it was becoming less and less white. At any given point until it is completely changed, we could have said, “This is white, but it is less white than the other can”. Is it possible for something to have esse and yet not be pure esse? If it is, then just like the case of the white paint, it is possible for something to have less esse than something that is pure esse. Earlier we talked about Mary having esse and a chunk of limestone having esse. We can attribute esse to both of them, but neither is pure esse: Mary is a rational animal, and the chunk of limestone is limestone. Thus, parallel to the white paint, we can say that they have less esse than something that has pure esse (God). But the limit of the analogy must be admitted. The difference between whiteness and esse is that whiteness is altered by something being added to it from without. Esse is altered by being contracted or limited from within, so to speak, by essences that are less than ipsum esse subsistens.

If it is not unintelligible for there to be degrees of esse, then Hughes cannot on this basis deny an identity between pure esse and pure perfection. Kretzmann’s rejection of the doctrine of God as ipsum esse subsistens depends on Hughes’s argument against it. But it would seem that Hughes has no sound argument to offer against it and so that Kretzmann has no support for his rejection of the doctrine.52

As I see it, on Thomas’s understanding of esse, whatever is pure esse must be subsistent and it cannot not be subsistent. If people wish to argue the contrary, then they have not understood what Thomas means by esse.

6. Conclusions

Thomas’s doctrine of God as ipsum esse subsistens certainly is not easy to understand. It is not surprising, therefore, that even so informed an interpreter as Kretzmann fails to understand it. But I hope that I have been able to clarify what Thomas means by ipsum esse subsistens, why he applies it to God, and some of his justification for doing so. In my view, Thomas has got things right. I also hope that I have been able to show the problems with the Kretzmann–Hughes interpretation of the doctrine and why it is untenable.