Article 13 — Whether the Trinity of persons in God can be known by natural reason

Thirteenth, it is asked whether the Trinity of persons in God can be known by natural reason? (Parallel texts: ST I.32.1; In I Sent., d. 3, q. 1, a. 4; In Boethius On the Trinity, q. 1, a. 4; Commentary on Romans, ch. 1, lect. 6.)

Obj. 1: It seems that it can, for the Gloss explains the passage, the invisible things of God . . . by the things that are made (Rom 1:13), in this way: invisible things refer to the person of the Father; eternal power to the person of the Son; divinity to the person of the Holy Spirit. (The Commentary of Peter Lombard on Romans 1:13, (PL 191:1328C).) Therefore, by natural reason we can arrive at a knowledge of the Trinity from creatures.

Obj. 2: That generative power is the first power was proved in this way: the order of powers follows the order of operations. But the first operation of all is to understand, for there is proof that an intellectual agent exists first, and in such an agent there is understanding, according to the manner of understanding, before willing or doing. Therefore, intellective power is the first of the powers. But intellective power is generative power, since every understanding begets its likeness in itself. Therefore, generative power is the first of the powers.

Obj. 3: Every equivocal is reduced to the univocal as every multitude is reduced to unity. (Boethius, On Arithmetic, bk. 2, ch. 1 (PL 63:1113).) But the procession of creatures from God is an equivocal procession, since creatures do not have the same name and definition as God. Therefore, according to natural reason we must assert that there pre-exists in God a univocal procession according to which God proceeds from God. Given this, there follows the distinction of the persons in God.

Obj. 4: One of the Glosses says (Glossa ordinaria, at Revelations 1:4, 6.1460; cf. William of Auxerre, Summa aurea, bk. 3, tract. 4.) that there has been no sect which has erred about the person of the Father. But it would be a very serious error about the person of the Father to say that he did not have a Son. Therefore, even the schools of philosophers who came to know God by natural reason have held Father and Son in God.

Obj. 5: As Boethius says, (Boethius, On Arithmetic, bk. 1, ch. 32 (PL 63:1110C).) equality precedes every inequality. But there is inequality between Creator and creature. Therefore, we must say that there was some equality in God before this inequality. But there cannot be equality in him unless there is distinction, for nothing is equal to itself, just as nothing is like itself, as Hilary says. (Hilary of Poitiers, On the Trinity, bk. 3, para. 23 (PL 10:92B).) Therefore, according to natural reason, we must assign distinction of persons to God.

Obj. 6: Natural reason comes to the conclusion that there is the greatest joy in God. But there is not the greatest enjoyment of any good without a companion, as Boethius says. (It is actually Seneca, Moral Letters to Lucilius, bk. 1, letter 6, para. 4.) Therefore, by natural reason we can know that there are distinct persons in God, and that by reason of their companionship there is joyful possession of goodness. (Cf. William of Auxerre, Summa aurea, bk. 1, ch. 2; Richard of St. Victor, On the Trinity, bk. 3, ch. 3 (PL 196:917); Alexander of Hales, Summa fratris Alexandri, part 1, inq. 1, tract. 3, q. 1, n. 76, memb. 2, ch. 1, 1:122; Bonaventure, In I Sent., d. 2, a. 1, q. 2, arg. 1.)

Obj. 7: Natural reason reaches the Creator from the likeness in the creature. But the likeness of the Creator is seen in the creature with reference not only to the essential attributes but also to the properties of the persons. Therefore, by natural reason we can arrive at the properties of the persons.

Obj. 8: Philosophers have had knowledge of God only from natural reason. But some philosophers have attained to knowledge of the Trinity. Thus, it is said in Heaven and Earth: through this number, three, we have applied ourselves to admiration of the grandeur of the Creator. (Aristotle, On the Heavens 1.1, 268a14.) Therefore.

Obj. 9: Augustine relates (Augustine, City of God, bk. 10, cc. 14 and 23 (PL 41:300).) that the philosopher Porphyry taught that there was God the Father and the Son begotten by him. Augustine also says (Augustine, Confessions, bk. 7, ch. 9 (PL 32:740), as Aquinas references in ST I.32.1, obj. 1.) that he found in certain books of Plato the prologue of St. John’s Gospel, from in the beginning was the Word down to, but not including, the Word was made flesh. (John 1:1–14.) The distinction of the persons is clearly shown in these words. Therefore, by natural reason one can reach knowledge of the Trinity.

Obj. 10: From natural reason, philosophers would have also conceded that God can say something. But to say something in God implies the utterance of the Word and the distinction of persons. Therefore, the Trinity of persons can be known by natural reason.

On the contrary (1), Hebrews 11:1 says: faith is the substance of things to be hoped for, the evidence of things that appear not. But those things which are known by natural reason are things that appear. Therefore, since the Trinity belongs to the articles of faith, it seems that it cannot be known by natural reason.

Furthermore (2), furthermore, Gregory says: (Gregory, Homilies on the Gospels, bk. 2, hom. 2 (PL 76:1197C); hom. 26.) belief does not have merit when human reason offers evidence for it. But it is in belief especially in the Trinity in which the merit of our faith consists. Therefore, it cannot be known by natural reason.

I answer that the Trinity of persons is known in two ways. In the first, it is known according to the properties by which the persons are distinguished. When these are known, the Trinity in God is really known. The second way is through essential notes which are appropriated to the persons, as power to the Father, wisdom to the Son, and goodness to the Holy Spirit. (Cf. Peter Lombard, Sentences, I, d. 34, ch. 3.) But it is impossible to know the Trinity perfectly through notes like these, for, even if in our minds we prescinded from the Trinity, those things would remain in God. But, once the Trinity is presupposed, attributes of this type are appropriated to the persons because of a certain likeness to properties of the persons.

With natural knowledge it is possible to know the things which are thus appropriated to the persons, but it is not at all possible to know the properties of the persons. The reason for this is that it is impossible for an action outside the range of the instruments of an agent to proceed from that agent. Thus, it is impossible to build with the art of the blacksmith, for this effect is outside the range of the instruments of the smith. Moreover, as the Commentator says, (Averroes, On the Soul, bk. 3, comm. 36.) in us first principles are, as it were, instruments of the agent intellect, and in virtue of its light, natural reason thrives in us. Hence, our natural reason cannot attain to knowledge of any of those things which are outside the range of first principles. But knowledge of first principles arises from sensible objects, as is clear from the Philosopher. (Aristotle, Posterior Analytics 2.19, 100a10.) But we cannot proceed from sensible things to knowledge of the properties of the persons in the way one reaches causes from effects. For everything that has the nature of cause in God pertains to his essence, since through his essence he is the cause of things. However, the properties of the persons are relations, through which the persons arc related not to creatures, but to each other. Hence, we cannot attain to the properties of the persons by natural knowledge.

Reply Sed Contra 1: That explanation of the Gloss is taken as referring to the things which are appropriated to the persons, not to the properties.

Reply Sed Contra 2: It can be made sufficiently clear from natural reason that intellective power is the first of the powers, but it cannot be shown that this intellective power is generative power. For, since in God the one who understands, the act of understanding, and what is understood is the same thing, natural reason does not force us to say that God, in understanding, begets something distinct from himself.

Reply Sed Contra 3: Every multiplicity supposes some unity and every equivocation supposes univocity, but every equivocal generation does not presuppose univocal generation. Rather, if we follow natural reason, the opposite is true, for equivocal causes are essential causes of a species. Hence, they exert causality on the whole species. But univocal causes are not essential causes of a species, but only in this or that individual. Consequently, a univocal cause does not exert causality with reference to the whole species. Otherwise, it would be its own cause, which is impossible. Therefore, the argument does not follow.

Reply Sed Contra 4: That Gloss should be taken of heretical sects which have sprung up in the Church. Accordingly, the sects of the gentiles are not included among them.

Reply Sed Contra 5: Even without supposing the distinction of persons, we can affirm equality in God, in so far as we say that his goodness is equal to his wisdom. Another answer can be based on a consideration of the two elements of equality, the cause of the equality and its terms. Unity is the cause of equality, but some number is the cause of other proportions. Hence, according to this consideration, equality precedes inequality, as unity precedes number. But the terms of equality are many. And these are not assumed to be prior to the terms of inequality. Otherwise, duality would have to precede every unity, for equality is first found in duality, but between unity and duality there is inequality.

Reply Sed Contra 6: What Boethius says should be understood of those things which do not have within them perfect goodness, but one needs the support of the other. For this reason, enjoyment is not complete without a companion. But God has within himself the fullness of joy. Hence, there is no need to posit companionship for the fullness of his enjoyment.

Reply Sed Contra 7: Although some aspects of creatures are like the properties of the persons, we cannot conclude from these likenesses that they are found in God in the same way. For the things which are distinguished in creatures are in the Creator without distinction.

Reply Sed Contra 8: Aristotle did not intend to put the number three in God, but he wanted to show the perfection of the number three from the fact that the ancients made use of it in sacrifices and prayers.

Reply Sed Contra 9: We should take the words of those philosophers as referring to things appropriated to the persons, not to properties.

Reply Sed Contra 10: From natural reason, philosophers have never thought that God speaks in so far as speaking implies distinction of persons, but only in so far as it is applied essentially to God.