Summa summae S. Thomae sive compendium theologiae

I say: There is one God, numerically and individually, in three Persons — that is, one and the same individual divine essence in three really distinct Persons: the Father unbegotten, the Son begotten, the Holy Spirit proceeding.

Proof from the Old Testament. 1° Genesis I, 26: God said: Let us make man in our image and likeness. — Behold plurality. And immediately after, v. 27: He created man in his own image. — Behold unity. 2° Genesis XVIII, 1–3: The Lord appeared to him [Abraham] in the valley of Mambre… And when he raised his eyes, there appeared to him three men standing near him; and when he saw them… he bowed to the ground. And said: Lord, if I have found favour in your eyes. Weighing these words, Augustine, Against Maximinus, bk. II, c. 26, n. 5, says: "He sees three, yet calls them not 'lords' but 'Lord,' because the Trinity indeed consists of three Persons, but there is one Lord God."

Proof from the New Testament. 1° Matthew XXVIII, 19: Baptizing them in the name of the Father, and of the Son, and of the Holy Spirit. In these words the unity of essence is indicated by the singular in the name — not in the names — and the Trinity of Persons by the enumeration: of the Father, and of the Son, and of the Holy Spirit. 2° 1 John V, 7: There are three who give testimony in heaven: the Father, the Word, and the Holy Spirit; and these three are one.

Against this most forceful testimony the Socinians attack two things: the authenticity of the text and its meaning. Regarding the authenticity of the text, they say that this seventh verse of chapter V of the First Epistle of John is spurious: (1) because it is not found in the more ancient and well-attested manuscripts; (2) because it was not cited by Athanasius, Hilary, Chrysostom, Ambrose, Gregory Nazianzen, and others against the Arians and Sabellians, even though it would have been most apt for refuting them. To the first objection, we admit that this verse, whether in full or in part, is not found in certain ancient manuscript copies; but it is found in far more of the most ancient and best-attested manuscripts.

That it is absent from a few copies could have occurred: (1) through the treachery of the Arians, who erased this text as too contrary to their error, as Jerome attests in his Prologue to the Catholic Epistles — if indeed that Prologue is Jerome's, a point currently debated by critics. But whatever the case, St. Ambrose frequently reproaches the Arians for this sort of fraud: On the Faith, bk. II, c. 15; bk. III, c. 16; On the Holy Spirit, bk. IV, c. 40. (2) The omission could also have arisen from a copyist's error: having arrived at the words of verse 7, There are three who give testimony, his eye skipped to verse 8, where the same words are repeated. This slip is common among copyists when the same words are repeated with scarcely any interval.

Moreover, our Vulgate edition was made according to the copies which were in everyday use among the faithful. These are far more difficult to corrupt, owing to their daily use and the certain risk of the fraud being detected; they therefore deserve far greater credibility than those that lie hidden in the corners of libraries, where through the negligence or malice of copyists they lie open to tampering and falsification.

To the second objection — that several Fathers did not cite this verse against heretics — I reply that several others did cite it. Tertullian cited it, Against Praxeas, c. 31; St. Cyprian, On the Unity of the Church; Jerome, in his Prologue to the Catholic Epistles; Cassiodorus, Fulgentius, and several others. This positive proof certainly outweighs the negative argument of the Socinians. Hence, that we do not read this verse having been cited in the writings of certain ancients is probably due to the fact that they happened upon a defective codex, or that not all their writings have come down to us, or that they were corrupted by enemies of the faith.¹

Regarding the meaning of this verse, the Socinians say that the words and these three are one do not signify unity of nature or substance, but unity of testimony — because in verse 8 following, of the spirit, the blood, and the water it is likewise said: and these three are one, which is not understood as unity of nature but of testimony, insofar as they concur in the same testimony about Christ, namely that he is the truth, just as the Father, the Son, and the Holy Spirit do. Reply 1°: These words of verse 8, and these three are one, are absent from many Latin codices. The Louvain correctors count fifteen in which they are not read. Innocent III, in the decretal found in Decretals III, tit. 41, c. In quadam, says that "in most codices" — probably Latin ones — "they are not found." The Greek codices do have them, yet not as cited, but thus: and these three are unto one [in unum], that is, they concur in one testimony. It is therefore rightly presumed that, through Arian fraud or copyist negligence, the word in dropped out of the Latin codices that contain these words. But even if our Vulgate does not read it that way, it must still be so explained as to correspond to the Greek original, so that the sense is: the spirit, the water, and the blood concur in attesting the same thing, namely that Christ is true man. And although in both verses there is a certain parallel in rendering testimony, it is not necessary that there be a parallel in the signification of the words and these three are one.

Reply 2°: Granted that these words express a parallel, that parallel is indeed found; for these three — Spirit, Water, and Blood — are in some manner substantially one. Let the sense then be: The Spirit, Water, and Blood gave testimony about Christ at the time of his passion: the Spirit, when he cried out and expired; the Blood and Water flowing from his side. And these three are substantially one, that is, they belong to one and the same human substance in Christ — just as the Father, the Son, and the Holy Spirit belong to one and the same divine substance — with this difference, however, that the divine substance is supremely simple and one, while the human substance is composite. 3° John X, 30: I and the Father are one. I and the Father are — behold the distinction of Persons; one — behold consubstantiality. Hence Augustine, Tract. XXXVI on John ch. VIII, says: "What he said, one, frees you from Arius; what he said, are, frees you from Sabellius." This passage was urged most forcefully by the Fathers against the heretics.

4° What could be plainer than John I, 1: In the beginning was the Word, and the Word was with God, and the Word was God?

Proof of the conclusion from Tradition. 1° From the form of Baptism which has been constantly in use from the very beginning of the Church; this form contains a profession of three Persons in one numerically identical substance, as we have considered above.

2° From the protest of the whole Church against the heresies that arose concerning this mystery — those of Sabellius, Arius, Macedonius, and others. From this it is clear that this is and has been the ancient and constant teaching of the faithful.

3° From the holy Fathers who in the first three centuries before the Council of Nicaea expressed this faith in their writings.

First century. Hermas, disciple of Paul, in the work called The Shepherd, bk. III, Similitudes 5 and 9. St. Clement, fellow worker of Paul and successor of Peter in the Roman See, Epistle to the Corinthians, n. 16 and n. 161 [sic — verify]. St. Dionysius the Areopagite, another disciple of St. Paul, On the Divine Names, c. 1. St. Ignatius Martyr, hearer of John the Evangelist, Epistles to the Ephesians and to the Magnesians.

Second century. St. Polycarp, disciple of both St. John the Evangelist and St. Ignatius, bishop of Smyrna, and with him the entire Church of Smyrna, in the letter written about St. Polycarp's martyrdom to the Churches of Pontus, in Eusebius, Ecclesiastical History, bk. IV, c. 15. St. Justin Martyr, Apology II. Athenagoras, the Christian philosopher, Apology for Christians to the Emperors. St. Irenaeus, disciple of St. Polycarp, bishop of Lyons and martyr, Against Heresies, bk. I, c. 2.

Third century. Clement of Alexandria, Paedagogus, bk. I, c. 6. Tertullian, Against Praxeas, c. 2, and On Modesty, c. 21. St. Cyprian, On the Unity of the Church, c. 4.

Finally, in the fourth century: at the Council of Nicaea in the year 325, against Arius, and at the Council of Constantinople in the year 381, against Macedonius, the Catholic faith concerning the Trinity and the consubstantiality of the Persons in one and undivided God was upheld — a faith which all the faithful have since unanimously professed in the Creed sung by the Church.

Objection 1: You will object first: This mystery is contrary to several principles known by the natural light [of reason], and firstly to this one: "Things which are the same as a third thing are the same as each other," upon which the whole art of syllogism rests. For the Persons are identified with the divine essence, and yet are really distinguished from one another. 2nd. This principle is not preserved: "Nothing produces its own being." For the producing Person and the produced Person have the same being. 3rd. It overturns this principle: "Person renders a nature incommunicable to another suppositum [subject];" because the nature which is in the Father is communicated to the Son and to the Holy Spirit. Therefore, this mystery is against reason, and thus impossible.

Response — I deny the antecedent.¹

To the first [objection] I answer, that this axiom must be understood of those things which are the same as a third thing in reality and in concept. In this sense it is explained that this one third thing is not virtually multiple, but that the extremes are united to it under the same formality and concept, not under a different one. Hence, although "action" is the same as "motion," and similarly "passion" [being acted upon], it does not follow that action and passion are the same; because in action a relation is implied as that from which motion exists in a movable object, but in passion as that which is from another. Similarly, although paternity is the same in reality as the divine essence, and similarly filiation, nevertheless these two in their proper concepts imply opposite relations, whence they are distinguished from each other.

So that you may understand this more deeply, note carefully that it is proper to an infinite thing to identify things with itself, preserving their formal concepts, when they do not imply imperfection. Thus, for example, the formal concept of wisdom, which is to know things through their highest cause, and likewise the formal concepts of justice, mercy, etc., are most perfectly preserved in God, notwithstanding their real identity with His essence. But the proper concept of a relation is to be opposed to its correlative and to be really distinguished from it; and accordingly the divine relations, notwithstanding their real identity with the essence, are opposed to each other relatively, and by reason of this opposition they are really distinguished from each other.

If you weigh these things well, you will easily solve whatever objections arise.

To the second I answer, that the Father does not produce His own being, but only communicates it; which He is able to do because that being is of such eminence and fecundity that, remaining the same, it can be possessed by multiple [Persons]: and since it is entirely the same in the Father and in the Son, it is not from the Father as from a cause with dependence, but as from a principle of origin.

To the third principle derived from the definition of person, I answer, this is understood by many in this way: that personality renders incommunicable not the nature in itself, but the composite itself and the person, or the nature reduplicatively as personated. Which is also verified in this mystery; for the Person of the Father, or the divine nature with the mode of paternity and as personated, is not communicated to another; for there is only one Father in the Godhead. Besides, granted that in created things it is understood otherwise—so that in them personality renders the nature itself incommunicable to another suppositum because a created nature, since it is finite, is fulfilled by a single personality—nevertheless, it must be verified in the Godhead in the first sense. This is both because, on account of its infinity and infinite fecundity, it is not equated or fulfilled by one personality, as a created nature is; and also because personality in the Godhead is not something absolute, as in created things, but something relative, and it is of the nature of a relative thing that it has a correlative.

Objection 2: From the infinity of the divine nature we gather, with St. Thomas, that it is one and unmultipliable. But a Person in the Godhead, as virtually distinct from the essence, is also infinite. Therefore, [there is only] one Person.

Response 1. I distinguish the minor premise. A Person in the Godhead, as virtually distinct from the essence, is infinite by reason of the essence which it includes: I concede; by reason of its relative concept precisely: I deny. For since under that respect it does not add perfection, it does not add infinity either, but abstracts from infinity and finitude.

Response 2. Granted the minor premise, I deny the consequence. The disparity is that, since a Person in the Godhead is constituted by a relation, as we shall see below, and this necessarily demands a term to which it refers, it does not imply infinity simply [in an absolute sense], but in a certain genus (e.g., paternity in the concept of paternity): and therefore it does not exclude just any other Person, but only another Father. But indeed, if there were multiple infinite essences, since they would not be opposed to each other relatively, nor consequently distinguished by reason of that opposition, they would have to be distinguished by some formal and essential concept which one would have and not the other, which therefore would not be infinite.

Objection 3: A reason cannot be assigned why there should be three Persons rather than two, or four, or more. Therefore.

Response. I deny the antecedent, and I assign a reason. In God there must be one unproduced Person and two produced, and no more. Therefore.—I prove the antecedent. Personal distinction in the Godhead, as we shall say below, is only according to the relation of origin; from which it follows 1st that there can be only one unproduced Person, since between unproduced Persons there is no given relation of origin. It follows 2nd that, since there are only two processions in the Godhead—one through the intellect, the other through the will (for procession in the Godhead is not considered according to a transient action, but an immanent one, which is twofold: to understand and to will)—there are also consequently only two proceeding Persons, or Persons terminating the twofold procession.—More on this below.