Summa Th. I EN Qu.39 a.5

Article: 5 Whether abstract essential names can stand for the person?

Objection: 1. It would seem that abstract essential names can stand for the person, so that this proposition is true, "Essence begets essence." For Augustine says (De Trin. vii, i, 2): "The Father and the Son are one Wisdom, because they are one essence; and taken singly Wisdom is from Wisdom, as essence from essence."

2. Further, generation or corruption in ourselves implies generation or corruption of what is within us. But the Son is generated. Therefore since the divine essence is in the Son, it seems that the divine essence is generated.

3. Further, God and the divine essence are the same, as is clear from what is above explained (Question [3], Article [3]). But, as was shown, it is true to say that "God begets God." Therefore this is also true: "Essence begets essence."

4. Further, a predicate can stand for that of which it is predicated. But the Father is the divine essence; therefore essence can stand for the person of the Father. Thus the essence begets.

5. Further, the essence is "a thing begetting," because the essence is the Father who is begetting. Therefore if the essence is not begetting, the essence will be "a thing begetting," and "not begetting": which cannot be.

6. Further, Augustine says (De Trin. iv, 20): "The Father is the principle of the whole Godhead." But He is principle only by begetting or spirating. Therefore the Father begets or spirates the Godhead.

On the contrary Augustine says (De Trin. i, 1): "Nothing begets itself." But if the essence begets the essence, it begets itself only, since nothing exists in God as distinguished from the divine essence. Therefore the essence does not beget essence.

I answer that Concerning this, the abbot Joachim erred in asserting that as we can say "God begot God," so we can say "Essence begot essence": considering that, by reason of the divine simplicity God is nothing else but the divine essence. In this he was wrong, because if we wish to express ourselves correctly, we must take into account not only the thing which is signified, but also the mode of its signification as above stated (Article [4]). Now although "God" is really the same as "Godhead," nevertheless the mode of signification is not in each case the same. For since this word "God" signifies the divine essence in Him that possesses it, from its mode of signification it can of its own nature stand for person. Thus the things which properly belong to the persons, can be predicated of this word, "God," as, for instance, we can say "God is begotten" or is "Begetter," as above explained (Article [4]). The word "essence," however, in its mode of signification, cannot stand for Person, because it signifies the essence as an abstract form. Consequently, what properly belongs to the persons whereby they are distinguished from each other, cannot be attributed to the essence. For that would imply distinction in the divine essence, in the same way as there exists distinction in the "supposita."

Reply to Objection: 1. To express unity of essence and of person, the holy Doctors have sometimes expressed themselves with greater emphasis than the strict propriety of terms allows. Whence instead of enlarging upon such expressions we should rather explain them: thus, for instance, abstract names should be explained by concrete names, or even by personal names; as when we find "essence from essence"; or "wisdom from wisdom"; we should take the sense to be, "the Son" who is essence and wisdom, is from the Father who is essence and wisdom. Nevertheless, as regards these abstract names a certain order should be observed, forasmuch as what belongs to action is more nearly allied to the persons because actions belong to "supposita." So "nature from nature," and "wisdom from wisdom" are less inexact than "essence from essence."

2. In creatures the one generated has not the same nature numerically as the generator, but another nature, numerically distinct, which commences to exist in it anew by generation, and ceases to exist by corruption, and so it is generated and corrupted accidentally; whereas God begotten has the same nature numerically as the begetter. So the divine nature in the Son is not begotten either directly or accidentally.

3. Although God and the divine essence are really the same, nevertheless, on account of their different mode of signification, we must speak in a different way about each of them.

4. The divine essence is predicated of the Father by mode of identity by reason of the divine simplicity; yet it does not follow that it can stand for the Father, its mode of signification being different. This objection would hold good as regards things which are predicated of another as the universal of a particular.

5. The difference between substantive and adjectival names consist in this, that the former carry their subject with them, whereas the latter do not, but add the thing signified to the substantive. Whence logicians are wont to say that the substantive is considered in the light of "suppositum," whereas the adjective indicates something added to the "suppositum." Therefore substantive personal terms can be predicated of the essence, because they are really the same; nor does it follow that a personal property makes a distinct essence; but it belongs to the "suppositum" implied in the substantive. But notional and personal adjectives cannot be predicated of the essence unless we add some substantive. We cannot say that the "essence is begetting"; yet we can say that the "essence is a thing begetting," or that it is "God begetting," if "thing" and God stand for person, but not if they stand for essence. Consequently there exists no contradiction in saying that "essence is a thing begetting," and "a thing not begetting"; because in the first case "thing" stands for person, and in the second it stands for the essence.

6. So far as Godhead is one in several "supposita," it agrees in a certain degree with the form of a collective term. So when we say, "the Father is the principle of the whole Godhead," the term Godhead can be taken for all the persons together, inasmuch as it is the principle in all the divine persons. Nor does it follow that He is His own principle; as one of the people may be called the ruler of the people without being ruler of himself. We may also say that He is the principle of the whole Godhead; not as generating or spirating it, but as communicating it by generation and spiration.

Article: 6 Whether the persons can be predicated of the essential terms?

Objection: 1. It would seem that the persons cannot be predicated of the concrete essential names; so that we can say for instance, "God is three persons"; or "God is the Trinity." For it is false to say, "man is every man," because it cannot be verified as regards any particular subject. For neither Socrates, nor Plato, nor anyone else is every man. In the same way this proposition, "God is the Trinity," cannot be verified of any one of the "supposita" of the divine nature. For the Father is not the Trinity; nor is the Son; nor is the Holy Ghost. So to say, "God is the Trinity," is false.

2. Further, the lower is not predicated of the higher except by accidental predication; as when I say, "animal is man"; for it is accidental to animal to be man. But this name "God" as regards the three persons is as a general term to inferior terms, as Damascene says (De Fide Orth. iii, 4). Therefore it seems that the names of the persons cannot be predicated of this name "God," except in an accidental sense.

On the contrary Augustine says, in his sermon on Faith [*Serm. ii, in coena Domini], "We believe that one God is one divinely named Trinity."

I answer that As above explained (Article [5]), although adjectival terms, whether personal or notional, cannot be predicated of the essence, nevertheless substantive terms can be so predicated, owing to the real identity of essence and person. The divine essence is not only really the same as one person, but it is really the same as the three persons. Whence, one person, and two, and three, can be predicated of the essence as if we were to say, "The essence is the Father, and the Son, and the Holy Ghost." And because this word "God" can of itself stand for the essence, as above explained (Article [4], ad 3), hence, as it is true to say, "The essence is the three persons"; so likewise it is true to say, "God is the three persons."

Reply to Objection: 1. As above explained this term "man" can of itself stand for person, whereas an adjunct is required for it to stand for the universal human nature. So it is false to say, "Man is every man"; because it cannot be verified of any particular human subject. On the contrary, this word "God" can of itself be taken for the divine essence. So, although to say of any of the "supposita" of the divine nature, "God is the Trinity," is untrue, nevertheless it is true of the divine essence. This was denied by Porretanus because he did not take note of this distinction.

2. When we say, "God," or "the divine essence is the Father," the predication is one of identity, and not of the lower in regard to a higher species: because in God there is no universal and singular. Hence, as this proposition, "The Father is God" is of itself true, so this proposition "God is the Father" is true of itself, and by no means accidentally.

Article: 7 Whether the essential names should be appropriated to the persons?

Objection: 1. It would seem that the essential names should not be appropriated to the persons. For whatever might verge on error in faith should be avoided in the treatment of divine things; for, as Jerome says, "careless words involve risk of heresy" [*In substance Ep. lvii.]. But to appropriate to any one person the names which are common to the three persons, may verge on error in faith; for it may be supposed either that such belong only to the person to whom they are appropriated or that they belong to Him in a fuller degree than to the others. Therefore the essential attributes should not be appropriated to the persons.

2. Further, the essential attributes expressed in the abstract signify by mode of form. But one person is not as a form to another; since a form is not distinguished in subject from that of which it is the form. Therefore the essential attributes, especially when expressed in the abstract, are not to be appropriated to the persons.

3. Further, property is prior to the appropriated, for property is included in the idea of the appropriated. But the essential attributes, in our way of understanding, are prior to the persons; as what is common is prior to what is proper. Therefore the essential attributes are not to be appropriated to the persons.

On the contrary the Apostle says: "Christ the power of God and the wisdom of God" (1Co 1,24).

I answer that For the manifestation of our faith it is fitting that the essential attributes should be appropriated to the persons. For although the trinity of persons cannot be proved by demonstration, as was above expounded (Question [32], Article [1]), nevertheless it is fitting that it be declared by things which are more known to us. Now the essential attributes of God are more clear to us from the standpoint of reason than the personal properties; because we can derive certain knowledge of the essential attributes from creatures which are sources of knowledge to us, such as we cannot obtain regarding the personal properties, as was above explained (Question [32], Article [1]). As, therefore, we make use of the likeness of the trace or image found in creatures for the manifestation of the divine persons, so also in the same manner do we make use of the essential attributes. And such a manifestation of the divine persons by the use of the essential attributes is called "appropriation."

The divine person can be manifested in a twofold manner by the essential attributes; in one way by similitude, and thus the things which belong to the intellect are appropriated to the Son, Who proceeds by way of intellect, as Word. In another way by dissimilitude; as power is appropriated to the Father, as Augustine says, because fathers by reason of old age are sometimes feeble; lest anything of the kind be imagined of God.

Reply to Objection: 1. The essential attributes are not appropriated to the persons as if they exclusively belonged to them; but in order to make the persons manifest by way of similitude, or dissimilitude, as above explained. So, no error in faith can arise, but rather manifestation of the truth.

2. If the essential attributes were appropriated to the persons as exclusively belonging to each of them, then it would follow that one person would be as a form as regards another; which Augustine altogether repudiates (De Trin. vi, 2), showing that the Father is wise, not by Wisdom begotten by Him, as though only the Son were Wisdom; so that the Father and the Son together only can be called wise, but not the Father without the Son. But the Son is called the Wisdom of the Father, because He is Wisdom from the Father Who is Wisdom. For each of them is of Himself Wisdom; and both together are one Wisdom. Whence the Father is not wise by the wisdom begotten by Him, but by the wisdom which is His own essence.

3. Although the essential attribute is in its proper concept prior to person, according to our way of understanding; nevertheless, so far as it is appropriated, there is nothing to prevent the personal property from being prior to that which is appropriated. Thus color is posterior to body considered as body, but is naturally prior to "white body," considered as white.

Article: 8 Whether the essential attributes are appropriated to the persons in a fitting manner by the holy doctors?

Objection: 1. It would seem that the essential attributes are appropriated to the persons unfittingly by the holy doctors. For Hilary says (De Trin. ii): "Eternity is in the Father, the species in the Image; and use is in the Gift." In which words he designates three names proper to the persons: the name of the "Father," the name "Image" proper to the Son (Question [35], Article [2]), and the name "Bounty" or "Gift," which is proper to the Holy Ghost (Question [38], Article [2]). He also designates three appropriated terms. For he appropriates "eternity" to the Father, "species" to the Son, and "use" to the Holy Ghost. This he does apparently without reason. For "eternity" imports duration of existence; "species," the principle of existence; and 'use' belongs to the operation. But essence and operation are not found to be appropriated to any person. Therefore the above terms are not fittingly appropriated to the persons.

2. Further, Augustine says (De Doctr. Christ. i, 5): "Unity is in the Father, equality in the Son, and in the Holy Ghost is the concord of equality and unity." This does not, however, seem fitting; because one person does not receive formal denomination from what is appropriated to another. For the Father is not wise by the wisdom begotten, as above explained (Question [37], Article [2], ad 1). But, as he subjoins, "All these three are one by the Father; all are equal by the Son, and all united by the Holy Ghost." The above, therefore, are not fittingly appropriated to the Persons.

3. Further, according to Augustine, to the Father is attributed "power," to the Son "wisdom," to the Holy Ghost "goodness." Nor does this seem fitting; for "strength" is part of power, whereas strength is found to be appropriated to the Son, according to the text, "Christ the strength [*Douay: power] of God" (1Co 1,24). So it is likewise appropriated to the Holy Ghost, according to the words, "strength [*Douay: virtue] came out from Him and healed all" (Lc 6,19). Therefore power should not be appropriated to the Father.

4. Likewise Augustine says (De Trin. vi, 10): "What the Apostle says, "From Him, and by Him, and in Him," is not to be taken in a confused sense." And (Contra Maxim. ii) "'from Him' refers to the Father, 'by Him' to the Son, 'in Him' to the Holy Ghost.'" This, however, seems to be incorrectly said; for the words "in Him" seem to imply the relation of final cause, which is first among the causes. Therefore this relation of cause should be appropriated to the Father, Who is "the principle from no principle."

5. Likewise, Truth is appropriated to the Son, according to Jn 14,6, "I am the Way, the Truth, and the Life"; and likewise "the book of life," according to Ps 39,9, "In the beginning of the book it is written of Me," where a gloss observes, "that is, with the Father Who is My head," also this word "Who is"; because on the text of Is 65,1, "Behold I go to the Gentiles," a gloss adds, "The Son speaks Who said to Moses, I am Who am." These appear to belong to the Son, and are not appropriated. For "truth," according to Augustine (De Vera Relig. 36), "is the supreme similitude of the principle without any dissimilitude." So it seems that it properly belongs to the Son, Who has a principle. Also the "book of life" seems proper to the Son, as signifying "a thing from another"; for every book is written by someone. This also, "Who is," appears to be proper to the Son; because if when it was said to Moses, "I am Who am," the Trinity spoke, then Moses could have said, "He Who is Father, Son, and Holy Ghost, and the Holy Ghost sent me to you," so also he could have said further, "He Who is the Father, and the Son, and the Holy Ghost sent me to you," pointing out a certain person. This, however, is false; because no person is Father, Son and Holy Ghost. Therefore it cannot be common to the Trinity, but is proper to the Son.

I answer that Our intellect, which is led to the knowledge of God from creatures, must consider God according to the mode derived from creatures. In considering any creature four points present themselves to us in due order. Firstly, the thing itself taken absolutely is considered as a being. Secondly, it is considered as one. Thirdly, its intrinsic power of operation and causality is considered. The fourth point of consideration embraces its relation to its effects. Hence this fourfold consideration comes to our mind in reference to God.

According to the first point of consideration, whereby we consider God absolutely in His being, the appropriation mentioned by Hilary applies, according to which "eternity" is appropriated to the Father, "species" to the Son, "use" to the Holy Ghost. For "eternity" as meaning a "being" without a principle, has a likeness to the property of the Father, Who is "a principle without a principle." Species or beauty has a likeness to the property of the Son. For beauty includes three conditions, "integrity" or "perfection," since those things which are impaired are by the very fact ugly; due "proportion" or "harmony"; and lastly, "brightness" or "clarity," whence things are called beautiful which have a bright color.

The first of these has a likeness to the property of the Son, inasmuch as He as Son has in Himself truly and perfectly the nature of the Father. To insinuate this, Augustine says in his explanation (De Trin. vi, 10): "Where---that is, in the Son---there is supreme and primal life," etc.

The second agrees with the Son's property, inasmuch as He is the express Image of the Father. Hence we see that an image is said to be beautiful, if it perfectly represents even an ugly thing. This is indicated by Augustine when he says (De Trin. vi, 10), "Where there exists wondrous proportion and primal equality," etc.

The third agrees with the property of the Son, as the Word, which is the light and splendor of the intellect, as Damascene says (De Fide Orth. iii, 3). Augustine alludes to the same when he says (De Trin. vi, 10): "As the perfect Word, not wanting in anything, and, so to speak, the art of the omnipotent God," etc.

"Use" has a likeness to the property of the Holy Ghost; provided the "use" be taken in a wide sense, as including also the sense of "to enjoy"; according as "to use" is to employ something at the beck of the will, and "to enjoy" means to use joyfully, as Augustine says (De Trin. x, 11). So "use," whereby the Father and the Son enjoy each other, agrees with the property of the Holy Ghost, as Love. This is what Augustine says (De Trin. vi, 10): "That love, that delectation, that felicity or beatitude, is called use by him" (Hilary). But the "use" by which we enjoy God, is likened to the property of the Holy Ghost as the Gift; and Augustine points to this when he says (De Trin. vi, 10): "In the Trinity, the Holy Ghost, the sweetness of the Begettor and the Begotten, pours out upon us mere creatures His immense bounty and wealth." Thus it is clear how "eternity," "species," and "use" are attributed or appropriated to the persons, but not essence or operation; because, being common, there is nothing in their concept to liken them to the properties of the Persons.

The second consideration of God regards Him as "one." In that view Augustine (De Doctr. Christ. i, 5) appropriates "unity" to the Father, "equality" to the Son, "concord" or "union" to the Holy Ghost. It is manifest that these three imply unity, but in different ways. For "unity" is said absolutely, as it does not presuppose anything else; and for this reason it is appropriated to the Father, to Whom any other person is not presupposed since He is the "principle without principle." "Equality" implies unity as regards another; for that is equal which has the same quantity as another. So equality is appropriated to the Son, Who is the "principle from a principle." "Union" implies the unity of two; and is therefore appropriated to the Holy Ghost, inasmuch as He proceeds from two. And from this we can understand what Augustine means when he says (De Doctr. Christ. i, 5) that "The Three are one, by reason of the Father; They are equal by reason of the Son; and are united by reason of the Holy Ghost." For it is clear that we trace a thing back to that in which we find it first: just as in this lower world we attribute life to the vegetative soul, because therein we find the first trace of life. Now "unity" is perceived at once in the person of the Father, even if by an impossible hypothesis, the other persons were removed. So the other persons derive their unity from the Father. But if the other persons be removed, we do not find equality in the Father, but we find it as soon as we suppose the Son. So, all are equal by reason of the Son, not as if the Son were the principle of equality in the Father, but that, without the Son equal to the Father, the Father could not be called equal; because His equality is considered firstly in regard to the Son: for that the Holy Ghost is equal to the Father, is also from the Son. Likewise, if the Holy Ghost, Who is the union of the two, be excluded, we cannot understand the oneness of the union between the Father and the Son. So all are connected by reason of the Holy Ghost; because given the Holy Ghost, we find whence the Father and the Son are said to be united.

According to the third consideration, which brings before us the adequate power of God in the sphere of causality, there is said to be a third kind of appropriation, of "power," "wisdom," and "goodness." This kind of appropriation is made both by reason of similitude as regards what exists in the divine persons, and by reason of dissimilitude if we consider what is in creatures. For "power" has the nature of a principle, and so it has a likeness to the heavenly Father, Who is the principle of the whole Godhead. But in an earthly father it is wanting sometimes by reason of old age. "Wisdom" has likeness to the heavenly Son, as the Word, for a word is nothing but the concept of wisdom. In an earthly son this is sometimes absent by reason of lack of years. "Goodness," as the nature and object of love, has likeness to the Holy Ghost; but seems repugnant to the earthly spirit, which often implies a certain violent impulse, according to Is 25,4: "The spirit of the strong is as a blast beating on the wall." "Strength" is appropriated to the Son and to the Holy Ghost, not as denoting the power itself of a thing, but as sometimes used to express that which proceeds from power; for instance, we say that the strong work done by an agent is its strength.

According to the fourth consideration, i.e. God's relation to His effects, there arise appropriation of the expression "from Whom, by Whom, and in Whom." For this preposition "from" [ex] sometimes implies a certain relation of the material cause; which has no place in God; and sometimes it expresses the relation of the efficient cause, which can be applied to God by reason of His active power; hence it is appropriated to the Father in the same way as power. The preposition "by" [per] sometimes designates an intermediate cause; thus we may say that a smith works "by" a hammer. Hence the word "by" is not always appropriated to the Son, but belongs to the Son properly and strictly, according to the text, "All things were made by Him" (Jn 1,3); not that the Son is an instrument, but as "the principle from a principle." Sometimes it designates the habitude of a form "by" which an agent works; thus we say that an artificer works by his art. Hence, as wisdom and art are appropriated to the Son, so also is the expression "by Whom." The preposition "in" strictly denotes the habitude of one containing. Now, God contains things in two ways: in one way by their similitudes; thus things are said to be in God, as existing in His knowledge. In this sense the expression "in Him" should be appropriated to the Son. In another sense things are contained in God forasmuch as He in His goodness preserves and governs them, by guiding them to a fitting end; and in this sense the expression "in Him" is appropriated to the Holy Ghost, as likewise is "goodness." Nor need the habitude of the final cause (though the first of causes) be appropriated to the Father, Who is "the principle without a principle": because the divine persons, of Whom the Father is the principle, do not proceed from Him as towards an end, since each of Them is the last end; but They proceed by a natural procession, which seems more to belong to the nature of a natural power.

Regarding the other points of inquiry, we can say that since "truth" belongs to the intellect, as stated above (Question [16], Article [1]), it is appropriated to the Son, without, however, being a property of His. For truth can be considered as existing in the thought or in the thing itself. Hence, as intellect and thing in their essential meaning, are referred to the essence, and not to the persons, so the same is to be said of truth. The definition quoted from Augustine belongs to truth as appropriated to the Son. The "book of life" directly means knowledge but indirectly it means life. For, as above explained (Question [24], Article [1]), it is God's knowledge regarding those who are to possess eternal life. Consequently, it is appropriated to the Son; although life is appropriated to the Holy Ghost, as implying a certain kind of interior movement, agreeing in that sense with the property of the Holy Ghost as Love. To be written by another is not of the essence of a book considered as such; but this belongs to it only as a work produced. So this does not imply origin; nor is it personal, but an appropriation to a person. The expression "Who is" is appropriated to the person of the Son, not by reason of itself, but by reason of an adjunct, inasmuch as, in God's word to Moses, was prefigured the delivery of the human race accomplished by the Son. Yet, forasmuch as the word "Who" is taken in a relative sense, it may sometimes relate to the person of the Son; and in that sense it would be taken personally; as, for instance, were we to say, "The Son is the begotten 'Who is,'" inasmuch as "God begotten is personal." But taken indefinitely, it is an essential term. And although the pronoun "this" [iste] seems grammatically to point to a particular person, nevertheless everything that we can point to can be grammatically treated as a person, although in its own nature it is not a person; as we may say, "this stone," and "this ass." So, speaking in a grammatical sense, so far as the word "God" signifies and stands for the divine essence, the latter may be designated by the pronoun "this," according to Ex 15,2: "This is my God, and I will glorify Him."


We now consider the persons in connection with the relations, or properties; and there are four points of inquiry:

(1) Whether relation is the same as person?

(2) Whether the relations distinguish and constitute the persons?

(3) Whether mental abstraction of the relations from the persons leaves the hypostases distinct?

(4) Whether the relations, according to our mode of understanding, presuppose the acts of the persons, or contrariwise?

Article: 1 Whether relation is the same as person?

Objection: 1. It would seem that in God relation is not the same as person. For when things are identical, if one is multiplied the others are multiplied. But in one person there are several relations; as in the person of the Father there is paternity and common spiration. Again, one relation exists in two person, as common spiration in the Father and in the Son. Therefore relation is not the same as person.

2. Further, according to the Philosopher (Phys. iv, text. 24), nothing is contained by itself. But relation is in the person; nor can it be said that this occurs because they are identical, for otherwise relation would be also in the essence. Therefore relation, or property, is not the same as person in God.

3. Further, when several things are identical, what is predicated of one is predicated of the others. But all that is predicated of a Person is not predicated of His property. For we say that the Father begets; but not that the paternity is begetting. Therefore property is not the same as person in God.

On the contrary in God "what is" and "whereby it is" are the same, according to Boethius (De Hebdom.). But the Father is Father by paternity. In the same way, the other properties are the same as the persons.

I answer that Different opinions have been held on this point. Some have said that the properties are not the persons, nor in the persons; and these have thought thus owing to the mode of signification of the relations, which do not indeed signify existence "in" something, but rather existence "towards" something. Whence, they styled the relations "assistant," as above explained (Question [28], Article [2]). But since relation, considered as really existing in God, is the divine essence Itself, and the essence is the same as person, as appears from what was said above (Question [39], Article [1]), relation must necessarily be the same as person.

Others, therefore, considering this identity, said that the properties were indeed the persons; but not "in" the persons; for, they said, there are no properties in God except in our way of speaking, as stated above (Question [32], Article [2]). We must, however, say that there are properties in God; as we have shown (Question [32], Article [2]). These are designated by abstract terms, being forms, as it were, of the persons. So, since the nature of a form requires it to be "in" that of which it is the form, we must say that the properties are in the persons, and yet that they are the persons; as we say that the essence is in God, and yet is God.

Reply to Objection: 1. Person and property are really the same, but differ in concept. Consequently, it does not follow that if one is multiplied, the other must also be multiplied. We must, however, consider that in God, by reason of the divine simplicity, a twofold real identity exists as regards what in creatures are distinct. For, since the divine simplicity excludes the composition of matter and form, it follows that in God the abstract is the same as the concrete, as "Godhead" and "God." And as the divine simplicity excludes the composition of subject and accident, it follows that whatever is attributed to God, is His essence Itself; and so, wisdom and power are the same in God, because they are both in the divine essence. According to this twofold identity, property in God is the same person. For personal properties are the same as the persons because the abstract and the concrete are the same in God; since they are the subsisting persons themselves, as paternity is the Father Himself, and filiation is the Son, and procession is the Holy Ghost. But the non-personal properties are the same as the persons according to the other reason of identity, whereby whatever is attributed to God is His own essence. Thus, common spiration is the same as the person of the Father, and the person of the Son; not that it is one self-subsisting person; but that as there is one essence in the two persons, so also there is one property in the two persons, as above explained (Question [30], Article [2]).

2. The properties are said to be in the essence, only by mode of identity; but in the persons they exist by mode of identity, not merely in reality, but also in the mode of signification; as the form exists in its subject. Thus the properties determine and distinguish the persons, but not the essence.

3. Notional participles and verbs signify the notional acts: and acts belong to a "suppositum." Now, properties are not designated as "supposita," but as forms of "supposita." And so their mode of signification is against notional participles and verbs being predicated of the properties.

Summa Th. I EN Qu.39 a.5