Summa Th. I EN Qu.41 a.4

Article: 4 Whether in God there is a power in respect of the notional acts?

Objection: 1. It would seem that in God there is no power in respect of the notional acts. For every kind of power is either active or passive; neither of which can be here applied, there being in God nothing which we call passive power, as above explained (Question [25], Article [1]); nor can active power belong to one person as regards another, since the divine persons were not made, as stated above (Article [3]). Therefore in God there is no power in respect of the notional acts.

2. Further, the object of power is what is possible. But the divine persons are not regarded as possible, but necessary. Therefore, as regards the notional acts, whereby the divine persons proceed, there cannot be power in God.

3. Further, the Son proceeds as the word, which is the concept of the intellect; and the Holy Ghost proceeds as love, which belongs to the will. But in God power exists as regards effects, and not as regards intellect and will, as stated above (Question [25], Article [1]). Therefore, in God power does not exist in reference to the notional acts.

On the contrary Augustine says (Contra Maxim. iii, 1): "If God the Father could not beget a co-equal Son, where is the omnipotence of God the Father?" Power therefore exists in God regarding the notional acts.

I answer that As the notional acts exist in God, so must there be also a power in God regarding these acts; since power only means the principle of act. So, as we understand the Father to be principle of generation; and the Father and the Son to be the principle of spiration, we must attribute the power of generating to the Father, and the power of spiration to the Father and the Son; for the power of generation means that whereby the generator generates. Now every generator generates by something. Therefore in every generator we must suppose the power of generating, and in the spirator the power of spirating.

Reply to Objection: 1. As a person, according to notional acts, does not proceed as if made; so the power in God as regards the notional acts has no reference to a person as if made, but only as regards the person as proceeding.

2. Possible, as opposed to what is necessary, is a consequence of a passive power, which does not exist in God. Hence, in God there is no such thing as possibility in this sense, but only in the sense of possible as contained in what is necessary; and in this latter sense it can be said that as it is possible for God to be, so also is it possible that the Son should be generated.

3. Power signifies a principle: and a principle implies distinction from that of which it is the principle. Now we must observe a double distinction in things said of God: one is a real distinction, the other is a distinction of reason only. By a real distinction, God by His essence is distinct from those things of which He is the principle by creation: just as one person is distinct from the other of which He is principle by a notional act. But in God the distinction of action and agent is one of reason only, otherwise action would be an accident in God. And therefore with regard to those actions in respect of which certain things proceed which are distinct from God, either personally or essentially, we may ascribe power to God in its proper sense of principle. And as we ascribe to God the power of creating, so we may ascribe the power of begetting and of spirating. But "to understand" and "to will" are not such actions as to designate the procession of something distinct from God, either essentially or personally. Wherefore, with regard to these actions we cannot ascribe power to God in its proper sense, but only after our way of understanding and speaking: inasmuch as we designate by different terms the intellect and the act of understanding in God, whereas in God the act of understanding is His very essence which has no principle.

Article: 5 Whether the power of begetting signifies a relation, and not the essence?

Objection: 1. It would seem that the power of begetting, or of spirating, signifies the relation and not the essence. For power signifies a principle, as appears from its definition: for active power is the principle of action, as we find in Metaph. v, text 17. But in God principle in regard to Person is said notionally. Therefore, in God, power does not signify essence but relation.

2. Further, in God, the power to act [posse] and 'to act' are not distinct. But in God, begetting signifies relation. Therefore, the same applies to the power of begetting.

3. Further, terms signifying the essence in God, are common to the three persons. But the power of begetting is not common to the three persons, but proper to the Father. Therefore it does not signify the essence.

On the contrary As God has the power to beget the Son, so also He wills to beget Him. But the will to beget signifies the essence. Therefore, also, the power to beget.

I answer that Some have said that the power to beget signifies relation in God. But this is not possible. For in every agent, that is properly called power, by which the agent acts. Now, everything that produces something by its action, produces something like itself, as to the form by which it acts; just as man begotten is like his begetter in his human nature, in virtue of which the father has the power to beget a man. In every begetter, therefore, that is the power of begetting in which the begotten is like the begetter.

Now the Son of God is like the Father, who begets Him, in the divine nature. Wherefore the divine nature in the Father is in Him the power of begetting. And so Hilary says (De Trin. v): "The birth of God cannot but contain that nature from which it proceeded; for He cannot subsist other than God, Who subsists from no other source than God."

We must therefore conclude that the power of begetting signifies principally the divine essence as the Master says (Sent. i, D, vii), and not the relation only. Nor does it signify the essence as identified with the relation, so as to signify both equally. For although paternity is signified as the form of the Father, nevertheless it is a personal property, being in respect to the person of the Father, what the individual form is to the individual creature. Now the individual form in things created constitutes the person begetting, but is not that by which the begetter begets, otherwise Socrates would beget Socrates. So neither can paternity be understood as that by which the Father begets, but as constituting the person of the Father, otherwise the Father would beget the Father. But that by which the Father begets is the divine nature, in which the Son is like to Him. And in this sense Damascene says (De Fide Orth. i, 18) that generation is the "work of nature," not of nature generating, but of nature, as being that by which the generator generates. And therefore the power of begetting signifies the divine nature directly, but the relation indirectly.

Reply to Objection: 1. Power does not signify the relation itself of a principle, for thus it would be in the genus of relation; but it signifies that which is a principle; not, indeed, in the sense in which we call the agent a principle, but in the sense of being that by which the agent acts. Now the agent is distinct from that which it makes, and the generator from that which it generates: but that by which the generator generates is common to generated and generator, and so much more perfectly, as the generation is more perfect. Since, therefore, the divine generation is most perfect, that by which the Begetter begets, is common to Begotten and Begetter by a community of identity, and not only of species, as in things created. Therefore, from the fact that we say that the divine essence "is the principle by which the Begetter begets," it does not follow that the divine essence is distinct (from the Begotten): which would follow if we were to say that the divine essence begets.

2. As in God, the power of begetting is the same as the act of begetting, so the divine essence is the same in reality as the act of begetting or paternity; although there is a distinction of reason.

3. When I speak of the "power of begetting," power is signified directly, generation indirectly: just as if I were to say, the "essence of the Father." Wherefore in respect of the essence, which is signified, the power of begetting is common to the three persons: but in respect of the notion that is connoted, it is proper to the person of the Father.

Article: 6 Whether several persons can be the term of one notional act?

Objection: 1. It would seem that a notional act can be directed to several Persons, so that there may be several Persons begotten or spirated in God. For whoever has the power of begetting can beget. But the Son has the power of begetting. Therefore He can beget. But He cannot beget Himself: therefore He can beget another son. Therefore there can be several Sons in God.

2. Further, Augustine says (Contra Maxim. iii, 12): "The Son did not beget a Creator: not that He could not, but that it behoved Him not."

3. Further, God the Father has greater power to beget than has a created father. But a man can beget several sons. Therefore God can also: the more so that the power of the Father is not diminished after begetting the Son.

On the contrary In God "that which is possible," and "that which is" do not differ. If, therefore, in God it were possible for there to be several Sons, there would be several Sons. And thus there would be more than three Persons in God; which is heretical.

I answer that As Athanasius says, in God there is only "one Father, one Son, one Holy Ghost." For this four reasons may be given.

The first reason is in regard to the relations by which alone are the Persons distinct. For since the divine Persons are the relations themselves as subsistent, there would not be several Fathers, or several Sons in God, unless there were more than one paternity, or more than one filiation. And this, indeed, would not be possible except owing to a material distinction: since forms of one species are not multiplied except in respect of matter, which is not in God. Wherefore there can be but one subsistent filiation in God: just as there could be but one subsistent whiteness.

The second reason is taken from the manner of the processions. For God understands and wills all things by one simple act. Wherefore there can be but one person proceeding after the manner of word, which person is the Son; and but one person proceeding after the manner of love, which person is the Holy Ghost.

The third reason is taken from the manner in which the persons proceed. For the persons proceed naturally, as we have said (Article [2]), and nature is determined to one.

The fourth reason is taken from the perfection of the divine persons. For this reason is the Son perfect, that the entire divine filiation is contained in Him, and that there is but one Son. The argument is similar in regard to the other persons.

Reply to Objection: 1. We can grant, without distinction, that the Son has the same power as the Father; but we cannot grant that the Son has the power "generandi" [of begetting] thus taking "generandi" as the gerund of the active verb, so that the sense would be that the Son has the "power to beget." Just as, although Father and Son have the same being, it does not follow that the Son is the Father, by reason of the notional term added. But if the word "generandi" [of being begotten] is taken as the gerundive of the passive verb, the power "generandi" is in the Son---that is, the power of being begotten. The same is to be said if it be taken as the gerundive of an impersonal verb, so that the sense be "the power of generation"---that is, a power by which it is generated by some person.

2. Augustine does not mean to say by those words that the Son could beget a Son: but that if He did not, it was not because He could not, as we shall see later on (Question [42], Article [6], ad 3).

3. Divine perfection and the total absence of matter in God require that there cannot be several Sons in God, as we have explained. Wherefore that there are not several Sons is not due to any lack of begetting power in the Father.


We now have to consider the persons as compared to one another: firstly, with regard to equality and likeness; secondly, with regard to mission. Concerning the first there are six points of inquiry.

(1) Whether there is equality among the divine persons?

(2) Whether the person who proceeds is equal to the one from Whom He proceeds in eternity?

(3) Whether there is any order among the divine persons?

(4) Whether the divine persons are equal in greatness?

(5) Whether the one divine person is in another?

(6) Whether they are equal in power?

Article: 1 Whether there is equality in God?

Objection: 1. It would seem that equality is not becoming to the divine persons. For equality is in relation to things which are one in quantity as the Philosopher says (Metaph. v, text 20). But in the divine persons there is no quantity, neither continuous intrinsic quantity, which we call size, nor continuous extrinsic quantity, which we call place and time. Nor can there be equality by reason of discrete quantity, because two persons are more than one. Therefore equality is not becoming to the divine persons.

2. Further, the divine persons are of one essence, as we have said (Question [39], Article [2]). Now essence is signified by way of form. But agreement in form makes things to be alike, not to be equal. Therefore, we may speak of likeness in the divine persons, but not of equality.

3. Further, things wherein there is to be found equality, are equal to one another, for equality is reciprocal. But the divine persons cannot be said to be equal to one another. For as Augustine says (De Trin. vi, 10): "If an image answers perfectly to that whereof it is the image, it may be said to be equal to it; but that which it represents cannot be said to be equal to the image." But the Son is the image of the Father; and so the Father is not equal to the Son. Therefore equality is not to be found among the divine persons.

4. Further, equality is a relation. But no relation is common to the three persons; for the persons are distinct by reason of the relations. Therefore equality is not becoming to the divine persons.

On the contrary Athanasius says that "the three persons are co-eternal and co-equal to one another."

I answer that We must needs admit equality among the divine persons. For, according to the Philosopher (Metaph. x, text 15,16, 17), equality signifies the negation of greater or less. Now we cannot admit anything greater or less in the divine persons; for as Boethius says (De Trin. i): "They must needs admit a difference [namely, of Godhead] who speak of either increase or decrease, as the Arians do, who sunder the Trinity by distinguishing degrees as of numbers, thus involving a plurality." Now the reason of this is that unequal things cannot have the same quantity. But quantity, in God, is nothing else than His essence. Wherefore it follows, that if there were any inequality in the divine persons, they would not have the same essence; and thus the three persons would not be one God; which is impossible. We must therefore admit equality among the divine persons.

Reply to Objection: 1. Quantity is twofold. There is quantity of "bulk" or dimensive quantity, which is to be found only in corporeal things, and has, therefore, no place in God. There is also quantity of "virtue," which is measured according to the perfection of some nature or form: to this sort of quantity we allude when we speak of something as being more, or less, hot; forasmuch as it is more or less, perfect in heat. Now this virtual quantity is measured firstly by its source---that is, by the perfection of that form or nature: such is the greatness of spiritual things, just as we speak of great heat on account of its intensity and perfection. And so Augustine says (De Trin. vi, 18) that "in things which are great, but not in bulk, to be greater is to be better," for the more perfect a thing is the better it is. Secondly, virtual quantity is measured by the effects of the form. Now the first effect of form is being, for everything has being by reason of its form. The second effect is operation, for every agent acts through its form. Consequently virtual quantity is measured both in regard to being and in regard to action: in regard to being, forasmuch as things of a more perfect nature are of longer duration; and in regard to action, forasmuch as things of a more perfect nature are more powerful to act. And so as Augustine (Fulgentius, De Fide ad Petrum i) says: "We understand equality to be in the Father, Son and Holy Ghost, inasmuch as no one of them either precedes in eternity, or excels in greatness, or surpasses in power."

2. Where we have equality in respect of virtual quantity, equality includes likeness and something besides, because it excludes excess. For whatever things have a common form may be said to be alike, even if they do not participate in that form equally, just as the air may be said to be like fire in heat; but they cannot be said to be equal if one participates in the form more perfectly than another. And because not only is the same nature in both Father and Son, but also is it in both in perfect equality, therefore we say not only that the Son is like to the Father, in order to exclude the error of Eunomius, but also that He is equal to the Father to exclude the error of Arius.

3. Equality and likeness in God may be designated in two ways---namely, by nouns and by verbs. When designated by nouns, equality in the divine persons is mutual, and so is likeness; for the Son is equal and like to the Father, and conversely. This is because the divine essence is not more the Father's than the Son's. Wherefore, just as the Son has the greatness of the Father, and is therefore equal to the Father, so the Father has the greatness of the Son, and is therefore equal to the Son. But in reference to creatures, Dionysius says (Div. Nom. ix): "Equality and likeness are not mutual." For effects are said to be like their causes, inasmuch as they have the form of their causes; but not conversely, for the form is principally in the cause, and secondarily in the effect.

But verbs signify equality with movement. And although movement is not in God, there is something that receives. Since, therefore, the Son receives from the Father, this, namely, that He is equal to the Father, and not conversely, for this reason we say that the Son is equalled to the Father, but not conversely.

4. In the divine persons there is nothing for us to consider but the essence which they have in common and the relations in which they are distinct. Now equality implies both ---namely, distinction of persons, for nothing can be said to be equal to itself; and unity of essence, since for this reason are the persons equal to one another, that they are of the same greatness and essence. Now it is clear that the relation of a thing to itself is not a real relation. Nor, again, is one relation referred to another by a further relation: for when we say that paternity is opposed to filiation, opposition is not a relation mediating between paternity and filiation. For in both these cases relation would be multiplied indefinitely. Therefore equality and likeness in the divine persons is not a real relation distinct from the personal relations: but in its concept it includes both the relations which distinguish the persons, and the unity of essence. For this reason the Master says (Sent. i, D, xxxi) that in these "it is only the terms that are relative."

Article: 2 Whether the person proceeding is co-eternal with His principle, as the Son with the Father?

Objection: 1. It would seem that the person proceeding is not co-eternal with His principle, as the Son with the Father. For Arius gives twelve modes of generation. The first mode is like the issue of a line from a point; wherein is wanting equality of simplicity. The second is like the emission of rays from the sun; wherein is absent equality of nature. The third is like the mark or impression made by a seal; wherein is wanting consubstantiality and executive power. The fourth is the infusion of a good will from God; wherein also consubstantiality is wanting. The fifth is the emanation of an accident from its subject; but the accident has no subsistence. The sixth is the abstraction of a species from matter, as sense receives the species from the sensible object; wherein is wanting equality of spiritual simplicity. The seventh is the exciting of the will by knowledge, which excitation is merely temporal. The eighth is transformation, as an image is made of brass; which transformation is material. The ninth is motion from a mover; and here again we have effect and cause. The tenth is the taking of species from genera; but this mode has no place in God, for the Father is not predicated of the Son as the genus of a species. The eleventh is the realization of an idea [ideatio], as an external coffer arises from the one in the mind. The twelfth is birth, as a man is begotten of his father; which implies priority and posteriority of time. Thus it is clear that equality of nature or of time is absent in every mode whereby one thing is from another. So if the Son is from the Father, we must say that He is less than the Father, or later than the Father, or both.

2. Further, everything that comes from another has a principle. But nothing eternal has a principle. Therefore the Son is not eternal; nor is the Holy Ghost.

3. Further, everything which is corrupted ceases to be. Hence everything generated begins to be; for the end of generation is existence. But the Son is generated by the Father. Therefore He begins to exist, and is not co-eternal with the Father.

4. Further, if the Son be begotten by the Father, either He is always being begotten, or there is some moment in which He is begotten. If He is always being begotten, since, during the process of generation, a thing must be imperfect, as appears in successive things, which are always in process of becoming, as time and motion, it follows that the Son must be always imperfect, which cannot be admitted. Thus there is a moment to be assigned for the begetting of the Son, and before that moment the Son did not exist.

On the contrary Athanasius declares that "all the three persons are co-eternal with each other."

I answer that We must say that the Son is co-eternal with the Father. In proof of which we must consider that for a thing which proceeds from a principle to be posterior to its principle may be due to two reasons: one on the part of the agent, and the other on the part of the action. On the part of the agent this happens differently as regards free agents and natural agents. In free agents, on account of the choice of time; for as a free agent can choose the form it gives to the effect, as stated above (Question [41], Article [2]), so it can choose the time in which to produce its effect. In natural agents, however, the same happens from the agent not having its perfection of natural power from the very first, but obtaining it after a certain time; as, for instance, a man is not able to generate from the very first. Considered on the part of action, anything derived from a principle cannot exist simultaneously with its principle when the action is successive. So, given that an agent, as soon as it exists, begins to act thus, the effect would not exist in the same instant, but in the instant of the action's termination. Now it is manifest, according to what has been said (Question [41], Article [2]), that the Father does not beget the Son by will, but by nature; and also that the Father's nature was perfect from eternity; and again that the action whereby the Father produces the Son is not successive, because thus the Son would be successively generated, and this generation would be material, and accompanied with movement; which is quite impossible. Therefore we conclude that the Son existed whensoever the Father existed and thus the Son is co-eternal with the Father, and likewise the Holy Ghost is co-eternal with both.

Reply to Objection: 1. As Augustine says (De Verbis Domini, Serm. 38), no mode of the procession of any creature perfectly represents the divine generation. Hence we need to gather a likeness of it from many of these modes, so that what is wanting in one may be somewhat supplied from another; and thus it is declared in the council of Ephesus: "Let Splendor tell thee that the co-eternal Son existed always with the Father; let the Word announce the impassibility of His birth; let the name Son insinuate His consubstantiality." Yet, above them all the procession of the word from the intellect represents it more exactly; the intellectual word not being posterior to its source except in an intellect passing from potentiality to act; and this cannot be said of God.

2. Eternity excludes the principle of duration, but not the principle of origin.

3. Every corruption is a change; and so all that corrupts begins not to exist and ceases to be. The divine generation, however, is not changed, as stated above (Question [27], Article [2]). Hence the Son is ever being begotten, and the Father is always begetting.

4. In time there is something indivisible---namely, the instant; and there is something else which endures---namely, time. But in eternity the indivisible "now" stands ever still, as we have said above (Question [10], Article [2] ad 1, Article [4] ad 2). But the generation of the Son is not in the "now" of time, or in time, but in eternity. And so to express the presentiality and permanence of eternity, we can say that "He is ever being born," as Origen said (Hom. in Joan. i). But as Gregory [*Moral. xxix, 21] and Augustine [*Super Ps 2,7] said, it is better to say "ever born," so that "ever" may denote the permanence of eternity, and "born" the perfection of the only Begotten. Thus, therefore, neither is the Son imperfect, nor "was there a time when He was not," as Arius said.

Article: 3 Whether in the divine persons there exists an order of nature?

Objection: 1. It would seem that among the divine persons there does not exist an order of nature. For whatever exists in God is the essence, or a person, or a notion. But the order of nature does not signify the essence, nor any of the persons, or notions. Therefore there is no order of nature in God.

2. Further, wherever order of nature exists, there one comes before another, at least, according to nature and intellect. But in the divine persons there exists neither priority nor posteriority, as declared by Athanasius. Therefore, in the divine persons there is no order of nature.

3. Further, wherever order exists, distinction also exists. But there is no distinction in the divine nature. Therefore it is not subject to order; and order of nature does not exist in it.

4. Further, the divine nature is the divine essence. But there is no order of essence in God. Therefore neither is there of nature.

On the contrary Where plurality exists without order, confusion exists. But in the divine persons there is no confusion, as Athanasius says. Therefore in God order exists.

I answer that Order always has reference to some principle. Wherefore since there are many kinds of principle---namely, according to site, as a point; according to intellect, as the principle of demonstration; and according to each individual cause---so are there many kinds of order. Now principle, according to origin, without priority, exists in God as we have stated (Question [33], Article [1]): so there must likewise be order according to origin, without priority; and this is called 'the order of nature': in the words of Augustine (Contra Maxim. iv): "Not whereby one is prior to another, but whereby one is from another."

Reply to Objection: 1. The order of nature signifies the notion of origin in general, not a special kind of origin.

2. In things created, even when what is derived from a principle is co-equal in duration with its principle, the principle still comes first in the order of nature and reason, if formally considered as principle. If, however, we consider the relations of cause and effect, or of the principle and the thing proceeding therefrom, it is clear that the things so related are simultaneous in the order of nature and reason, inasmuch as the one enters the definition of the other. But in God the relations themselves are the persons subsisting in one nature. So, neither on the part of the nature, nor on the part the relations, can one person be prior to another, not even in the order of nature and reason.

3. The order of nature means not the ordering of nature itself, but the existence of order in the divine Persons according to natural origin.

4. Nature in a certain way implies the idea of a principle, but essence does not; and so the order of origin is more correctly called the order of nature than the order of essence.

Article: 4 Whether the Son is equal to the Father in greatness?

Objection: 1. It would seem that the Son is not equal to the Father in greatness. For He Himself said (Jn 14,28): "The Father is greater than I"; and the Apostle says (1Co 15,28): "The Son Himself shall be subject to Him that put all things under Him."

2. Further, paternity is part of the Father's dignity. But paternity does not belong to the Son. Therefore the Son does not possess all the Father's dignity; and so He is not equal in greatness to the Father.

3. Further, wherever there exist a whole and a part, many parts are more than one only, or than fewer parts; as three men are more than two, or than one. But in God a universal whole exists, and a part; for under relation or notion, several notions are included. Therefore, since in the Father there are three notions, while in the Son there are only two, the Son is evidently not equal to the Father.

On the contrary It is said (Ph 2,6): "He thought it not robbery to be equal with God."

I answer that The Son is necessarily equal to the Father in greatness. For the greatness of God is nothing but the perfection of His nature. Now it belongs to the very nature of paternity and filiation that the Son by generation should attain to the possession of the perfection of the nature which is in the Father, in the same way as it is in the Father Himself. But since in men generation is a certain kind of transmutation of one proceeding from potentiality to act, it follows that a man is not equal at first to the father who begets him, but attains to equality by due growth, unless owing to a defect in the principle of generation it should happen otherwise. From what precedes (Question [27], Article [2]; Question [33], Articles [2],3), it is evident that in God there exist real true paternity and filiation. Nor can we say that the power of generation in the Father was defective, nor that the Son of God arrived at perfection in a successive manner and by change. Therefore we must say that the Son was eternally equal to the Father in greatness. Hence, Hilary says (De Synod. Can. 27): "Remove bodily weakness, remove the beginning of conception, remove pain and all human shortcomings, then every son, by reason of his natural nativity, is the father's equal, because he has a like nature."

Reply to Objection: 1. These words are to be understood of Christ's human nature, wherein He is less than the Father, and subject to Him; but in His divine nature He is equal to the Father. This is expressed by Athanasius, "Equal to the Father in His Godhead; less than the Father in humanity": and by Hilary (De Trin. ix): "By the fact of giving, the Father is greater; but He is not less to Whom the same being is given"; and (De Synod.): "The Son subjects Himself by His inborn piety"---that is, by His recognition of paternal authority; whereas "creatures are subject by their created weakness."

2. Equality is measured by greatness. In God greatness signifies the perfection of nature, as above explained (Article [1], ad 1), and belongs to the essence. Thus equality and likeness in God have reference to the essence; nor can there be inequality or dissimilitude arising from the distinction of the relations. Wherefore Augustine says (Contra Maxim. iii, 13), "The question of origin is, Who is from whom? but the question of equality is, Of what kind, or how great, is he?" Therefore, paternity is the Father's dignity, as also the Father's essence: since dignity is something absolute, and pertains to the essence. As, therefore, the same essence, which in the Father is paternity, in the Son is filiation, so the same dignity which, in the Father is paternity, in the Son is filiation. It is thus true to say that the Son possesses whatever dignity the Father has; but we cannot argue---"the Father has paternity, therefore the Son has paternity," for there is a transition from substance to relation. For the Father and the Son have the same essence and dignity, which exist in the Father by the relation of giver, and in the Son by relation of receiver.

3. In God relation is not a universal whole, although it is predicated of each of the relations; because all the relations are one in essence and being, which is irreconcilable with the idea of universal, the parts of which are distinguished in being. Persons likewise is not a universal term in God as we have seen above (Question [30], Article [4]). Wherefore all the relations together are not greater than only one; nor are all the persons something greater than only one; because the whole perfection of the divine nature exists in each person.

Summa Th. I EN Qu.41 a.4