Commentaria in Summam contra Gentiles, Liber IV

Having shown that the arguments of Arius against the Catholic faith are invalid, St. Thomas wishes to show from what has been said that neither do those passages which Photinus and Sabellius adduced from Sacred Scripture in favor of their opinions confirm their errors ¹. And first, he answers Photinus; second, Sabellius ².

I. As to the first ³, he says regarding the first authority that Christ does not say that power was given to Him as though He then received it anew, but because the power which He had received from eternity began to appear in Him made man through the victory He had had by rising again.

To the second, it is said that the Son of God is said to be made, not simply, but according to the flesh, through the assumption of human nature, in the way it is said, The Word was made flesh, as is clear through the Apostle. — Likewise He is said to be predestined according to human nature, which pertains to the Son; for its union with the Son was not from human merits, but from the grace of God predestining.

To the third, it is said, first, that it must be referred to the human nature, in which was the humility of the passion, that God is said to have exalted Christ through the merit of the passion. — It is said, second, that the Father's having given Him a name which is above every name is to be understood in this way: that the name belonging to the Son from eternal birth was to be manifested in the faith of the peoples as belonging to the incarnate Son.

To the fourth, it is said that Peter understood that God made Jesus Christ and Lord according to the human nature, in which He began to have from time what in the nature of divinity He had from eternity.

II. As to the second ⁴, an answer is given first to the authorities adduced by Sabellius concerning the unity of the deity. And it is said that they do not conflict with the Catholic faith, which posits that the Father and the Son are not two gods but one God, as was said above.

To what Christ says, The Father abiding in me, etc., it is said that it shows the unity of essence, but not the unity of person. For if there were one person of the Father and the Son, it would not fittingly be said that the Father is in the Son and conversely; since the same supposit is not properly said to be in itself, but only by reason of parts, in the way a whole is sometimes said to be in itself because the parts are in the whole; for what belongs to the parts is accustomed to be attributed to the whole. This mode is not fitting in divine things, in which there cannot be parts.

It is said, second, that from the unity of essence it is apparent how the Father is in the Son and the Son in the Father. For since the Father is His essence, it remains that in whatever the essence of the Father is, in that is the Father. Hence, since the essence of the Father is in the Son, it follows that the Father is in the Son; and by the same reason the Son is in the Father. And thus by the same word the error both of Sabellius and of Arius is refuted.

III. For the evident understanding of what is said here in the second place, it must be considered, first, that one thing being in another includes both a distinction between them, because the same cannot be in itself; and a certain union between them, for if any things are altogether separated, one of them is not said to be in the other. The Son is therefore said to be in the Father and conversely, inasmuch as, since they are two really distinct supposits, they have one essence in number, which is the same for both supposits. For the unity of essence in both supposits alone is not the reason for this, but this unity together with the all-inclusive identity of the supposit with the essence; as is clear from St. Thomas on John, ch. 14 ⁵; and in this chapter; and also in the First Part, q. 42, a. 5. Hence such a unity of essence, and its identity with the supposit, is the reason that one is said to be in the other. But the distinction between the persons themselves is presupposed for this inexistence.

IV. It must be considered, second, that although whenever one is said to be in another, there must be some distinction between them; yet where one is really in the other, any distinction whatsoever does not suffice, but it is necessary that there be a real distinction between them. And therefore, where one is not really distinguished from the other, it cannot properly be said that one is in the other: although, if they are distinguished according to reason, one can be said to be in the other according to reason, the other requisite conditions being present. On account of this, the divine essence is not said to be really in the Son, if we speak properly, but only according to the mode of understanding and signifying, for it is not really distinguished from the Son: but the Father is well and truly in the Son really, from whom He is distinguished, since He is the same as His essence and does not abandon it, and His essence is in the Son.

From this is clear the solution to the arguments of Aureolus recounted by Capreolus in I Sent., d. 19 ⁶, when he argues that by the same reason it could be concluded that the Son was in the Son, and that the Son was in the essence. For it is clear that it is very well argued that the Father is in the Son because His substance is in Him, because the Father and the Son are really distinguished. But by this reason the same cannot be concluded concerning those things that are adduced: because the Son is really distinguished neither from Himself nor from His essence.

2. But if it be urged that the reason adduced by St. Thomas does not seem to conclude that the Father is in the Son really, but only according to reason: because the Father does not seem to be in the Son by any other reason than that His essence is in Him, since He is not in the Son except by reason of the essence; but the essence is not in the Son except according to reason, in line with what was said above: — it is answered that, although the essence of the Father, inasmuch as it is also in the Son, is that by reason of which the Father is said to be in the Son, nevertheless it is not required that the essence be in the Son and in the Father in the same mode; because, notwithstanding the numerical unity of the essence of the Father and of the Son, there is between the Father and the Son a real distinction according to relative opposition. And therefore, just as the real distinction of the persons stands together with the numerical unity of the essence, so with the existence of reason of the essence in the Son and in the Father, there stands the real existence of the Father in Him, on account of their real distinction.

Let no one think, however, that I am saying that the divine essence is not in the Son really, as though the reality itself of the essence were not attributed to the Son. For I do not mean this: but that, since by that preposition in a distinction is imported, at least presuppositively, the reality of the essence by which it is really identified with the Son does not have that real distinction which is imported when one is said to be in another really, although the reality of the essence is in the Son, that is, is not extrinsic to the Son.

V. It must be noted, third, that this mode of being in is not properly any of those modes of being in something that are enumerated by the Philosopher in IV Physics ⁷; but nevertheless by a certain remote likeness it can be reduced to some of them. For as is held from the doctrine of St. Thomas in I Sent., d. 19, q. 3, a. 2, ad 1, we can speak of the being of one person in another in two ways: in one way, according to being; in another way, according to intellect ⁸. In the first way, it is reduced to that mode by which a genus is in its species (understand this, as I said, by a remote reduction): because, since on account of the unity of essence the Father is said to be in the Son because His essence is in the Son, it is reduced to that mode to which it would be reduced if the essence were said to be in the Son just as in material things the essence is in the supposit, from which it is in some way really distinguished, as was shown above ⁹. But this mode is reduced to that mode by which a genus is in a species.

In the second way, however, it is reduced to that mode by which something is in its efficient or originating principle, and conversely the originating in the originated, if they are taken relatively: because, namely, one belongs to the intellect and notion of the other, just as one relative enters into the notion of the other. And it is in this sense that what St. Thomas says in the First Part, in the place cited, to the first, is understood ¹⁰.

VI. It is clear then from these things that, properly speaking, the Father's being in the Son according to being, and conversely, is nothing other than the Father, really distinct from the Son, being consubstantial with Him and of the same numerical essence with Him, and conversely.

In Scotus, however, in I Sent., d. 19 ¹¹, the Father's being in the Son is His being present to Him by the presence of a subsistent to a subsistent, with the unity of nature demanding such a presence. Which comes to the same thing as what we have said. — See the rest in Capreolus, in the place cited ¹².

Concerning what is said, that by one word the error of Arius and of Sabellius is refuted, it must be noted that, since, as has been shown, the Father's being in the Son shows both their personal distinction, and the unity of essence in them and their consubstantiality; by the fact that it imports a distinction of persons, the error of Sabellius positing that there is one person of the Father and of the Son is excluded; but by the fact that it imports consubstantiality and unity of essence, the error of Arius saying that the Son is a creature and is not of the same essence with the Father is excluded.