Thomas Aquinas on Creation (or How to Read Thomas Aquinas)
1. The Distinction Between God and the World

William G. Witt

AquinasThe distinction between God and the world introduced by the notion of creatio ex nihilo is the chief contribution that the Christian doctrine of creation brings to the discussion of the relation between God and the world. (1) Thomas Aquinas’s understanding of this distinction becomes more evident when compared with the Islamic philosopher Ibn Sina’s (980-1037) notion of creation as the necessary overflow of contingent being from the one necessary being. (2) Aquinas was greatly indebted to Ibn Sina (whom he quotes hundreds of times), especially for the latter’s distinction between essence and existence, a distinction that Ibn Sina borrowed from his predecessors, but developed more fully. Thomas’s originality is shown in the manner in which he modified this distinction between essence and existence (under the influence of the Christian understanding of creation as a free act of God) to emphasize the radical contingency of created beings.

In the philosophy of Ibn Sina, the distinction between essence and existence is subservient to a more fundamental distinction—the distinction between (what later philosophers would call) necessary and contingent being. The most general concept of being divides into two categories: that which is “necessary through itself” (necessary being) and that which is “necessary through another” (contingent being). The distinction between the two categories lies in causality. That which is necessary through itself has no cause. It exists absolutely necessarily. That which is necessary through another is caused. Its existence is contingent in itself, but necessary through that whose existence is necessary in itself, i.e., the first cause (necessary being) (Healing, 1.6., Scientific Knowledge, 18-20). (Because of his Neoplatonic understanding of emanation or necessary creation, Ibn Sina presupposed that contingent being, while not necessary in itself, must be necessary through another.) Ibn Sina argued further that there could be only one necessary being or first cause because to posit the existence of a multiplicity of necessary beings leads to logical incoherence. This necessary being (in contrast to all contingent beings) must be absolutely simple, without composition or constituent parts (Healing, 1.7. Scientific Knowledge, 21-23). The logic here is rather straightforward. If God were composite rather than simple, he would not be necessary through himself, but would be necessary through the parts of which he were composed. (3)

Ibn Sina was able to elucidate this distinction between necessary and contingent being more thoroughly by introducing a further distinction—that between essence and existence. Ibn Sina found the Aristotelian hylomorphic theory inadequate to account for the actual existence of the individual thing. For Aristotle, substance is composed of form and matter. Form, however, is a principle of being and does not exist by itself. Matter, as pure potentiality, can exist only as actualized by form. To account for the actual existence of the individual thing, Ibn Sina found it necessary to supplement the formula of form and matter with the additional element of existence. The individual substance, therefore, is composed of essence (form and matter) plus existence (Healing, 2.4. 6.1). (4)

Ibn Sina notes that it is possible to distinguish between the “what” (essence) of a thing and its “whether” (existence). The question “What is a thing?” is distinct from the question “Does it exist?” It is also possible to conceive of a thing without in any way implying that it exists; we can think of imaginary creatures, e.g.. hippogriffs, unicorns. To conceive of the definition of a thing (the essence in itself) does not, therefore, necessitate its existence. In order for an individual thing actually to exist, it must (Ibn Sina claimed) receive its existence from outside itself—as an “accident” or attribute of the individual essence, which “comes to it” (Healing 1.5.6). Ibn Sina maintained that the world is made up of contingent beings that come to exist and cease to exist—in which essence and existence can be distinguished, and which receive their existence from another. This Other is the absolutely simple and necessary being in whom essence and existence are identical.

The background for Ibn Sina’s distinction between the necessary being (whose existence is necessary through itself and in whom essence and existence are identical) and contingent beings (whose existence is necessary through another and in which essence and existence are distinct) is found in his identification of creation with a Neoplatonic doctrine of emanation. Ibn Sina argued that since the necessary being is completely actualized fullness of being and consequently absolute goodness, it necessarily tends to diffuse its being and goodness and thus creates necessarily. Since the first being is necessary being, its attributes are also necessary and it must necessarily create. Since the necessary being is eternal, creation must be eternal. It follows that the necessary being does not create freely; nor could any other world have been created than the one that now exists. The existence of the necessary being is simultaneous with that of the world produced out of necessity (Scientific Knowledge, 38-57). This interpretation of creation as a necessary emanation is, of course, in radical contrast to the distinction between God and the world maintained in the Judeo-Christian and (orthodox) Islamic traditions. (5)

As one examines the manner in which Thomas Aquinas articulated the distinction between God and the world, it becomes evident that he echoes many of the themes and formulations of Ibn Sina. However, one also recognizes that Thomas was working from a different vantage point. The Christian understanding of creation influenced his use of the philosophical tools he borrowed from Ibn Sina, and Thomas pushed the distinctions elaborated by the latter—e.g., those between necessary and contingent existence, between essence and existence—in a more thoroughgoing direction. Aquinas’s theology is distinguished from that of Ibn Sina by his introduction of a new distinction—the “distinction between the world understood as possibly not having existed and God understood as possibly being all that there is with no diminution of goodness or greatness.” (6)

Thomas’s dependence on Ibn Sina is apparent in his appropriation of lbn Sina’s distinction between contingent beings and necessary being. In the third of Aquinas’s well-known quinquae viae, the “Five Ways” to demonstrate the existence of God, Thomas argued that the existence of contingent beings demands the existence of a necessary being to bring them into and maintain them in existence (Summa Theologiae 1.2.3). The argument as presented in the Summa is dependent on Maimonides, who had borrowed it from Ibn Sina, and it is really more a succinct summary than a fully developed presentation.

There are, Thomas said, things that come into existence and cease to exist—things that “can be but need not be” (possibilia esse et non esse). Everything that exists cannot be contingent in this manner, however, because, if it is possible for a thing not to exist, it once did not exist. If, however, everything need not be, at one time there would have been nothing in existence (aliquando nihil fuit in rebus)—in which case there would be nothing now in existence (since from nothing, nothing comes). Since, however, it is patently obvious that something does now exist, there must be a necessary being—a being whose existence is necessary in itself (aliquid quod est per se necessarium), which is not dependent on any other being for its existence, and which is the cause of the existence of contingent beings.

This is not the place to discuss the validity of the cosmological argument. Our concern is to notice the extent to which Aquinas’s presentation of the argument points toward the Christian understanding of creation—towards God being understood as the only necessary existent and to the world understood as possibly not having existed at all. There is in the Summa a significant departure from the manner in which the argument was developed by Ibn Sina. For Ibn Sina, the argument worked from cause to effects as from premises to conclusion. As F. Rahman notes, Ibn Sina’s argument points to God as the ground of the world, i.e., given God we can understand the existence of the world—“the world as a whole is contingent, but given God it becomes necessary.” (7) Thomas approached the argument from the opposite end. Rather than arguing in an a a priori manner from cause to effect, Thomas argued a posteriori from the existence of actual effects to the necessity of their cause—from the existence of one actually existing entity to the existence of another. In other words, Thomas did not argue from the conceptual to the real (as did Ibn Sina, Anselm, and Descartes) but from the real to the real, from the existence of actual entities to a necessary existent. Presumably, if God had not created, there could be no cosmological argument for his existence.

By arguing that contingent beings are incapable of accounting for their own existence, Aquinas presumed the distinction between essence and existence in created things. Thomas developed this distinction dialectically in On Being and Essence (De Ente et Essentia), where he followed Ibn Sina fairly closely, and introduced it again in Summa Theologiae 1.3.4 in the context of his discussion of the simplicity of God. Aquinas’s presentation of the essence/existence distinction (like his discussion of the Five Ways) is extremely compressed. He argued that whatever belongs to a thing and is not itself part of the essence of that thing must either be caused by its essence (i.e., be an accident) or derive from an exterior cause. That is, since existence can be distinguished from essence (whether something is can be distinguished from what it is), existence must be either an accident (derive from the nature of the thing) or be received from an extrinsic principle. It is impossible, however, for existence to derive from intrinsic principles (it is not an accident), since nothing is self-caused. It follows that if essence and existence can be distinguished in a thing (that something is, is not identical with what it is), then its existence must have an external cause. This distinction between essence and existence in creatures reflects, therefore, a derived existence.

The source of the existence of creatures is, of course, God, the first efficient cause and “the beginning and end of all things” (S.T. 1.2). Since God is the first cause and primary existent, it is impossible for his existence to derive from another. He cannot partake in or receive existence, and so (in contrast to creatures), the distinction between essence and existence cannot obtain in God. Essence and existence must be identical in his case, and God must himself, therefore, be existence. God is self-identical self-subsisting existence (ipsum esse per se subsistens). In short, God is not a being, but Being Itself.

The argument points toward the Christian distinction between God and creatures in that (again) Thomas’s starting point is not conceptual, i.e., an abstract distinction between essence and existence. He argued from the actual existence of individual contingent things to a distinction between essence and existence. Furthermore, by not allowing that existence is a property of essences, Thomas avoided the “essentialist” implication that existence is an accident, attribute, or predicate. Existence is rather esse—the act of existing, “to be.” And God, who alone exists without cause, is not described as infinite substance but as the pure act of existing (purus actus essendi). Since God’s essence and his existence are identical (God is his existence), “He who is” is the most appropriate name for God (S.T. l.13.11)

Here is one of the most crucial advances in Thomas’s philosophical theology over the essentialist ontologies that had preceded him, and which are still so uncritically embraced. In identifying “existence” with an activity, as a verb, something that one does—“X exists” is a statement in the same manner as “X runs” and not “X is blue”—Aquinas made a conceptual advance over Aristotle’s philosophy that was clearly influenced by the Christian theology of creation. By identifying Aristotle’s notion of “act” with esse, Aquinas introduced a dynamism into the notion of being that forces a basic choice as to the primary of the actual over the possible, the really existing over the conceptual. (8) And, as will be seen below, Aquinas is easily able to tie his notion of God as the “pure act” of existing (purus actus essendi; actus = past participle of agere) with God as the “agent” (agens = present participle of agere) who brings other beings into existence by sharing with them the act of existing. In contrast, Aristotle’s Unmoved Mover is a “pure act” of “Self-Thinking Thought” which knows or wills nothing outside itself, and which performs no actions. Aristotle’s Unmoved Mover is not a Creator.

To say that God is self-subsisting existence is not to say anything positive about God in the sense of giving us a proper concept of Deity. Thomas’s use of the distinction between essence and existence to point to the boundaries between creature and Creator is not so much part of a positive theology that would enable us to get a “handle” on God, but reflects more his use of the via negativa to enable us to say something about what God is not. His description of God as self-subsisting existence lies in the context of his general discussion of the divine simplicity and is not an attempt to develop a doctrine of God, but rather an indication of one of the “ways in which God does not exist.” (S.T. 1.3). (9)

In contemporary philosophy of religion, this notion of divine simplicity has been challenged as incoherent. Certainly if one begins one’s discussion of God with a summary of divine attributes (omnipotence, omniscience, eternity, etc.) or weights the discussion with the Platonically loaded language of divine properties, it does indeed seem peculiar that a number of attributes or properties can be combined to form a single and simple divine nature.

Space precludes a detailed defense of divine simplicity, but a case can be made that without affirming divine simplicity, we cannot provide an account of divine transcendence that adequately distinguishes God from creatures. David Burrell has argued that simplicity functions in Aquinas’s philosophical theology as the best way to maintain that God simply is. Insofar as creatures are radically dependent on God’s free intentional creative act, they receive a contingent existence. Accordingly, the distinction between God and creatures precludes predicating any characteristics of God that are actually unique to creatures. Composition implies dependency, and Divine simplicity is part of a negative theology that denies any limitations of God that are characteristic of composite creatures. In developing this “negative theology” (in some ways similar to that of Maimonides), Aquinas discussed God only as “the beginning and end of all things and of reasoning creatures especially” (1.2).

By saying what God is not, Thomas was able more clearly to articulate the distinction between God and creatures. Thus, in the first eleven questions of the Summa, Aquinas is not developing a positive doctrine of God at all. What many have read as a plurality of “attributes ” are actually denials of limitation. Eternity means not being limited by the transition from potency to act that is entailed in temporal change; Omnipresence means not being limited by space—God is wherever he brings creatures into existence. Rather than speaking of “attributes,” Aquinas emphasizes what Burrell calls the “formal features” of divine simplicity. These “formal features” of the divine nature are simply an unpacking of what it means to be simple and are not an assertion of composition. (10)

Thomas’s identification of God as the One in whom essence and existence are identical is an example of the manner in which Aquinas was able to distinguish the absolutely simple Creator—the beginning and end of all things—from all composite creatures of which he is the cause, by denying of God all the imperfections that belong properly not to God, but to creatures. Thomas summed up his position by saying that the divine simplicity (although one) can be shown in many ways:

For God . . . is not composed of extended parts, since he is not a body; nor of form and matter; nor does he differ from his own nature; nor his nature from his existence; nor can one distinguish in him genus and difference, nor substance and accidents. It is clear then that there is no way in which God is composite and he must be altogether simple (1.3.7).

This distinction between creatures and Creator is one that seems to be easy to misconstrue. The natural empirical bent of the human mind draws it toward “pagan” ways of imagining the relation between the finite and the infinite as if it were the relation between two finite composite beings. Since, as Thomas would have maintained, all knowledge originates in sense perception—physical creatures are the first things we come to know—it is all too easy to conceive of the divine as simply a bigger and more powerful creature, the first being, perhaps, among other beings, but a being nonetheless. The images that naturally arise in the imagination cannot help but lead us to picture God and creatures as competing “natures” against the background of a common reality, and the questions that are often raised reflect this, e.g., how is it possible to reconcile divine omnipotence and human freedom?

The dilemma typically presents itself in the form of one of two alternatives—either limiting the divine in some manner so as to allow for necessities, i.e., positing a finite god, or else eliminating the natural necessities by either allowing God to overwhelm them or else identifying them in some way with God, i.e., determinism and/or pan(en)theism. Christian supernaturalism is constantly threatened by either “naturalism” on the one hand, or “anti-naturalism” on the other. (11)

In dealing with two such cases of confusion Thomas Aquinas further clarified the distinction between creatures and Creator he had already established in his discussion of the divine simplicity by pointing towards a solution along the lines of the Christian understanding of creation. In the first case, Thomas responded to the questioner who understandably perceives God’s infinity to be a threat to creaturely autonomy. The idea of self-identity itself ordinarily places limits on things. The fact that something is this or that means that it is not something else, and must, therefore, be finite. And, as Thomas’s imaginary objector pointed out, God is not a stone or a piece of wood. He cannot, therefore, be infinite in substance. If he were, there would be no “room” for stones and wood. The same idea is often implicitly present in contemporary theological discussions in which it is sometimes maintained that in creating the world, God has necessarily placed limitations on himself; by positing something outside his own existence, God has voluntarily accepted limitations to his power and freedom. Otherwise God would be the only “thing” that could exist.

In replying to the objection, Thomas again pointed to the identity of God’s nature and existence. Aquinas appealed to the very notion of self-identity that had prompted the question initially. God is indeed self-identical. He is himself and not another. However, God’s self-identity is unlike that of creatures, who are usually individuated by matter. Rather, God’s self-identity lies in his being self-subsisting act of existing. To be God simply is to be. That is enough to distinguish him from created things. Thomas said, “The very fact that God’s existence itself subsists (per se subsistens) and as such is limitless (dicitur infinitum) distinguishes it from everything else, and sets other things aside from it.” (1.7.1, reply obj. 3). God is infinite because of who he is, or, better, because he is who he is—self-subsisting to be, the pure act of self-identical existence, and in that self-identical existence he is infinitely distinguished from all other beings. Creatures, in contrast to God, are finite and cannot be infinite (even angels, who are not differentiated by matter) because as created forms they receive existence, and their existence must, therefore, be expressed in and contracted to a determinate nature (1.7.2).

At the opposite extreme from the position to which Thomas found himself opposed in the above discussion is that which tends to overlook “natural necessities”—which resolves the question of the relation between God and the world by merging the two into identity, i.e., pan(en)theism. Aquinas confronted this notion in the Summa first in 1.3.8— “whether God enters into the composition of other things.” He addressed three expressions of this tendency here: (1) those who affirm that God is the world-soul; (2) those who have said that God is the formal principle of all things; and (3) those who have “most foolishly” identified God with prime matter (material causality).

Thomas’s rather abrupt reply perhaps indicates his exasperation with a position to which he could not afford much respect. He dealt negatively with the above suggestions by simply reaffirming what he had maintained earlier—that God is the beginning and end of all things. As first efficient cause, God cannot be identical numerically with the form of the thing that he has made. And as pure act of existing, he cannot enter into composition with anything else. To do so would violate his simplicity (1.3.8, reply).

Thomas more clearly defined his positive views on this problem in S.T. 1.8—“God’s existence in things”—where he established that God’s existence in things is that of an agent, and in 1.9—“God’s unchangeableness”—where Aquinas introduced the doctrine of creatio ex nihilo, and thus affirmed two central elements of the Christian distinction between God and creatures over against any sense of Neoplatonic emanation or necessary creation of creatures by God.

That the God of Thomas is the God or Abraham, Isaac, and Jacob, and not the God of the philosophers—if by “God of the philosophers” one means the static and aloof metaphysical principle caricatured as the “god of natural theology”or “classical theism”—is evident in Aquinas’s affirmation that God’s action in creation is that of an agent, and is, therefore, free. According to Thomas, God can be present to things in two ways. First, as an operative cause, God is present to things by giving them existence. Thomas said:

God exists in everything, not indeed as part of their substance or as an accident but as an agent is present to that in which its action is taking place . . . since it is God’s nature to exist (Deus sit ipsum esse per suam essentiam), he it must be who properly causes existence in creatures . . . (1.8.2, reply).

During the entire time in which something exists, God must be present to it, not only giving it existence, but also maintaining it in existence. Contingent creatures continue to be only as they are sustained in existence by the creative act of the One whose existence is necessary. Aquinas also noted (and this in a bit aside from our present discussion) that God is present in a second way, in a special manner, in rational creatures that actually know and love him, i.e., by grace.

Thomas’s affirmation that God’s action in creation is that of an agent is complemented by his assertion that God brings creatures into existence from nothing. Creatures do not have to be and might not have been at all. (This is the central element in the Christian distinction noted by Sokolowski—“the distinction between the world understood as possibly not having existed and God understood as possibly being all that there is.” (12)) Aquinas denied that creatures possess any “created potentiality” before their actual existence (a denial of essentialism or of rationes seminales?) since “nothing [created] exists eternally, but [creatures exist] simply because God had the power to bring them into existence.” God has not only brought creatures into existence through his free creative act, but (as we noted in the previous paragraph) sustains them in existence, and without his continued creative activity, they would fall back into nothingness. Thomas said,

So just as before things existed on their own it was in the Creator’s power for them to exist, so now that they do exist on their own it is in the Creator’s power for them not to exist . . . . God, who was able to bring them into existence out of nothing . . . is able to reduce them again from existence to nothingness (1.9.2, reply).

This introduction of the Christian doctrine of creation from nothing in the context of a discussion of the divine unchangeableness is easily overlooked by contemporary critics of “classical theism,” for whom creatio ex nihilo is (often) assumed as a given, but for whom the doctrine of divine immutability is perceived as a classic example of the contamination of Christian theology by the static categories of pagan Hellenistic philosophy. The apparent ease, however, with which Aquinas incorporated the Christian understanding of creation into his discussion of the divine immutability points to the manner in which Thomas modified the philosophical tools handed to him by his predecessors, using their vocabulary to express Christian theological conceptions that stand in stark contrast to Hellenistic notions of the relation between the divine and the world.


The central category borrowed by Thomas Aquinas from Ibn Sina was the latter’s distinction between essence and existence, a distinction that Ibn Sina used to express a Neoplatonic notion of the necessary emanation of contingent beings from the one necessary existent. Yet Aquinas modified this distinction to express the Christian understanding of creation in a manner that might well have perplexed the Islamic philosopher. Thomas agreed with Ibn Sina in postulating a distinction between God and creatures. According to Aquinas, God is the one simple source of all that is—the beginning and end of all things in whom essence and existence are identical, which means that to be God is simply to be. Creatures are those contingent beings in whom essence and existence are distinct. They do not have to be.

But Thomas interpreted this distinction in a radically Christian manner. There was no room in his theology for a scheme of emanation, or for treating “being” as a super-genus that encompasses both God and creatures. According to Thomas, God is that pure act of existence who radically exists because that is his nature, and who might well have been the only existent. Creatures are contingent not merely in the sense that their existence is not self-explanatory and is received (albeit) necessarily through another. Rather they are radically contingent in the sense that God has brought them into existence from nothing by a gratuitous free act. If God had so chosen, they might not have existed at all. According to Thomas, existence (for creatures) is a pure gift.

1. The central theme of Sokolowski, The God of Faith and Reason.

2. Ibn Sina’s writings are relatively unavailable in translation. A rather difficult English translation of the Healing (al-Shifa), 1.6.7; 6.1.2, is found in Philosophy in the Middle Ages, ed. Arthur Hyman, James J. Walsh, (NY: Harper & Row, 1967), 240-254. A more readable French translation is La Metaphysique du Shifa, trans. Georges C. Anawati (Paris: Vrin, 1978). An acceptable English translation of the Book of Scientific Knowledge (Dnish Nma-i l’) is The Metaphysics of Avicenna (Ibn Sina), trans. Parviz Morewedge, (NY: Columbia University Press, 1973).

3. A. M. Goichon, “The Philosopher of Being,” Avicenna Commemoration Volume (Calcutta: Iran Society, 1956); L. De Raeymaeker, “L’etre selon Avicenne et selon S. Thomas D’Aquin,” Avicenna Commemoration Volume; Fazlur Rahman, “Essence and Existence in Avicenna,” ed. Richard Hunt, Raymond Klibansky, Medieval and Renaissance Studies 4 (London, 1958); Fadlou Shehadi, Metaphysics in Islamic Philosophy (Delmar, NY: Caravan Books, 1982).

4. F. Rahman, “Ibn Sina,” History of Muslim Philosophy, ed. N, N. Sharif, 2 vols. (Wiesbaden, 1963), 1:483.

5. Seyyed Hessein Nasr, An Introduction to Islamic Cosmological Doctrines: Conceptions of Nature and Methods Used for its Study by the khwan al-Safa’, al-Biruni, and Ibn Sna, rev. ed. (London: Thames and Hudson, 1978), 202.

6. Sokolowski, 23.

7. Rahman, 482-483.

8. See especially, David Burrell’s “Aquinas and Scotus: Contrary Patterns for Philosophical Theology,” Theology and Dialogue: Essays in Conversation with George Lindbeck, Bruce D. Marshall, ed. (University of Notre Dame Press, 1990), 105-129. And of course, this is the central theme of Burrell’s Aquinas: God and Action (University of Notre Dame Press, 1979.

9. David Burrell, Aquinas: God and Action, ch. 2.

10. David Burrell, Aquinas: God and Action (Notre Dame, IN: University of Notre Dame Press, 1979, 3-54; Knowing the Unknowable God (Notre Dame, IN: University of Nore Dame Press, 1986), 3-70.

11. See Sokolowski, 21-22; Eugene Fairweather, “Christianity and the Supernatural,” New Theology No. 1, ed. Martin Marty and Dean Peerman (NY: Macmillan, 1964), 237 ff.

12. Sokolowski, 23.