¹ Summa Theologiae I, 44, IC.; Contra Gentiles II, 15. (Summa Theologiae will be abbreviated hereafter as S.T.; Contra Gentiles as C.G.)

² The doctrine of a real distinction between essence and existence in creatures is commonly held to be the kernel of St. Thomas's metaphysics. E.g.: Gilson speaks of “the central place of this thesis in Thomistic metaphysics.” The Christian Philosophy of St. Thomas Aquinas, (New York) 1956, p. 11Google Scholar; “This doctrine, whose place in Thomism is central …”, ibid., p. 34. For Maritain, , the “real distinction between essence and existence in all that is not God” is “The most fundamental and most characteristic metaphysical thesis of Aristotelianism as re-thought by Thomas Aquinas.” Existence and the Existent, (New York) c. 1948, p. 35Google Scholar.

³ As in C.G. II, 52, 2: “But existence, insofar as it is existence, cannot be diverse: but it can be diversified through something which is in addition to existence; as the existence of a stone is other than the existence of a man.”

⁴ As in De Potentia I, I, 3c.: “The existence of man is limited to the species of man, because it is received in the nature of the species of man, and the same is the case with the existence of horse, or of any creature at all. But the existence of God, since it is not received in anything, is not limited to any mode of the perfection of existing, but has all existence in itself, and so, just as existence taken universally can extend to an infinite number of things, so the divine existence is infinite …” Cf. S.T. I, 50, 2 ad 4; C.G. I, 43, 8.

⁵ Note that here the word “essence” is used directly, enabling us to avoid the cumbersome circumlocutions needed in dealing with the argument from the Contra Gentiles, in which the phrase “that which is of the essence” has been employed.

⁶ Against the suspicion that a causeless essence, or a causeless what-is-of-the-essence is involved here, it may be objected that St. Thomas's doctrine is that, for caused things, the existence makes the essence to be: the causing of the essence and of what-is-of-the-essence is precisely the causing of existence to accrue to the essence. It must be pointed out that this explanation assumes some basis for an essence-existence distinction (perhaps potency-act) while it destroys the basis implied in noting that the existence, precisely, belongs to the thing through a cause.

⁷ Cf. the following expressions in another argument from this same chapter: “Existence itself pertains to all other things from the first agent by a certain participation. But that which pertains to something through participation, is not the substance of that thing.” (C.G. II, 52, 9).

⁸ “Each and every created thing, just as it does not have existence, except from another, and considered in itself is nothing, in the same way needs to be conserved in the good appropriate to its nature by another.” S.T. I-II, 109, 2, ad 2. (Italics mine)

⁹ Cf. S.T. I, 9, 2c; S.T. I, 46, 1, ad 1.

¹⁰ De Potentia III, 5, ad 2: “… before it ‘the quiddity, the essence’ has existence, it is nothing.” It should be noted that such statements may tend to give the imaginational picture of a “nothing” which receives existence and so becomes a “something.” The notion here would probably be better expressed by saying “there is no essence before it has existence.”

¹¹ “Simultaneously with giving existence, God produces that which receives existence.” De Pot. III, 1, ad 17.

¹² According to S.T. I, 45, 1 ad 3, “ex nihilo” can have two legitimate meanings when applied to creation. It can refer to the order of creation: there is no existence of creatures preceding creation. Or it can mean that there is no matter upon which the creator works, no “material cause”: “Something is made from nothing, that is, it is not made from something.” Our concern is with the latter meaning. “…creation is the production of some thing according to its entire substance, presupposing nothing which is either uncreated or created by anything.” S.T. I, 65, 3c.

¹³ “First agent” does not mean first in time, but first in order. God is called the first agent because there is no agent in order above him. He is the agent who does not have an agent acting upon him. The expression is equivalent to “first cause,” which means “uncaused cause.”

¹⁴ The quoted passage occurs in an article in which St. Thomas is arguing that in the Blessed Trinity the Son is “generated” by the Father. Encountering the objection that the existence of anything generated is received existence, he answers that the existence of the Son is not received in a subject, but is “accepted” from the Generator.

¹⁵ For St. Thomas, characteristically, there is a duality here also: the creature cannot be the relation: “… according as creation is truly a relation, the creature is its subject, and is before it in existence, as a subject to an accident. But it has a certain ratio of priority on the part of the object towards which it is said, which object is the source of the creature.” (S.T. I, 45, 3, ad 3.)