Introduction

            Although the usage of the concept of person in Trinitarian discourse predated Aquinas, he, originally, explained how best the concept is to be understood when predicated of the Trinity. This is one of his ingenuity and original contributions to the Trinitarian discourse. Before him, St Augustine had discussed the usage of the concept in Trinitarian discourse. However, Augustine did not bother himself with expounding the concept; that was not his interest in his psychological theology of the Trinity. Augustine confessed that the term sprang from the necessity of speaking. For Augustine, there is threeness in God, and the concept is simply employed to name this threeness.

It sought then what three it should call them, and answered substances or persons; by which names it did not intend diversity to be meant, but singleness to be denied: that not only unity might be understood therein from the being called one essence, but also Trinity from the being called three substances or persons.

...Seeing that they are three, let us ask what three they are, and what they have in common. For the being the Father is not common to them, so that they should be interchangeably fathers to one another... Neither are they three Sons, since the Father there is not the Son, nor is the Holy Spirit. Neither three Holy Spirits, because the Holy Spirit also... is neither the Father nor the Son. What three therefore? For if three persons, then that which is meant by person is common to them.

Augustine did not explain to us the appropriateness of the concept and its predication to God. It took the genius of Aquinas to explain this. Aquinas, aware of the difficulty of the concept, takes up the tedious task of explaining how the concept applies to the Trinity. In this, he succeeds in showing us that the difficulty of the concept arises from a misappropriation of the concept which stems from applying the meaning of a human person to the divine person.

            In this paper, we will first highlight Aquinas’ discourse on the simplicity of God. Then, we would discuss how it is possible to speak of distinctions in God in spite of his simplicity. Next, we shall show how Aquinas predicated person of God in speaking of the distinctions in God. Then, we shall demonstrate how the misappropriateness of the concept Person is, in fact, not misappropriateness after all, but only due to a misconception. Before all this, let us brief do a conceptual clarification of our terms.

Conceptual Clarification

            We need to clarify some terms like Substance, Subsistence, Essence, Hypostasis and Person. Substance can be used in two ways. In one sense, it means the quiddity (essence) of a thing, signified by its definition. In this sense, substance is called essence. In another sense, substance means a subject or suppositum of a nature, i.e. a subsisting individual or a subsistence or a hypostasis. A suppositum is any concrete distinct single instance of any nature. A subsistence is a thing that exists in itself, that does not inhere in another. A hypostasis is a subsisting individual. When a hypostasis is of a rational nature, it is a person. A person is a rational hypostasis, a subsistent individual of a rational nature.

The Simplicity of God

            In discussing the simplicity of God, Aquinas argues that in God, suppositum and nature are identical. In things that are not composed of matter and form, individualization is not due to individual matter, rather the very forms are individualized of themselves. In other words, the forms themselves are subsisting supposita, i.e. one form cannot be individualized into more than one suppositum; each form is its suppositum. For each form, there can only be one suppositum. Thus, if there are two supposita, there must be two different forms. One suppositum exhausts an essence. God is his Godhead. God is the only single instance of the Divine essence, unlike in humans where a human being is only one instance of the several instances of humanness. Hence, the suppositum and the essence are identical in God. The simplicity of God is absolute.

There is neither composition of quantitative parts in God, since He is not a body; nor composition of matter and form; nor does His nature differ from His "suppositum"; nor His essence from His existence; neither is there in Him composition of genus and difference, nor of subject and accident. Therefore, it is clear that God is nowise composite, but is altogether simple.

That God is One can also be argued from the infinity of His Perfection. God comprehends in Himself the whole perfection of being. If then many gods existed, they would necessarily differ from each other. Something, therefore, would belong to one, which did not belong to another. And if this were a privation, one of them would not be absolutely perfect, but if a perfection, one of them would be without it. So it is impossible for many gods to exist. Furthermore, the reason why any singular thing is this particular thing is because it cannot be communicated to many. The Divine essence is incommunicable. It is impossible that many Gods should exist.

            Since the simplicity of God allows us to speak only of one suppositum of God, how then are we to speak of the distinctions in the Trinity? At least from the preceding, it is clear that the Father, the Son and the Holy Spirit are not three instances of the divine essence. They are not each a subjective individualization of the divine essence, for we have seen that the divine essence is not communicable; there is only One God, not three Gods. The three are not three supposita of the divine essence in the sense of individual substances as there are three men. Also, the three cannot be conceived of as three equal parts of one divine Substance, for God is not a composite; He is altogether simple. When we speak of three persons in God, it should not be understood that the three persons add up to One God and that each of the persons is not Gods, but only the three together is God. Each of the persons is God and the three are God, not Gods. They each possess perfectly the divine essence (so each person is God) and since there can only be one suppositum of this divine essence, the three are God, not Gods. More so, we cannot simply dismiss these distinctions in God and simply posit God as One with three modes/facets. In the light of all the preceding, how is it still possible to talk of distinctions in God?

How is Distinction possible in God who is altogether Simple

            To understand the distinctions in God, we have to go to the source, the origin: Procession in God. There is procession in God. But this procession is not an outward procession corresponding to the act tending to external matter, rather it is an inward procession corresponding to the act remaining within the agent.

This applies most conspicuously to the intellect, the action of which remains in the intelligent agent. For whenever we understand, by the very fact of understanding there proceeds something within us, which is a conception of the object understood, a conception issuing from our intellectual power and proceeding from our knowledge of that object. This conception is signified by the spoken word; and it is called the word of the heart signified by the word of the voice ... Procession, therefore, is not to be understood from what it is in bodies, either according to local movement or by way of a cause proceeding forth to its exterior effect, as, for instance, like heat from the agent to the thing made hot. Rather it is to be understood by way of an intelligible emanation, for example, of the intelligible word which proceeds from the speaker, yet remains in him.

            Owing to the divine simplicity, there can be no diversity in God. Since inward procession is possible without diversity, procession is possible in God. If inward procession were impossible without diversity, there could be no procession in God; for in God, there could be no diversity. We have to understand what is meant by non-diversity here. Non-diversity here does not rule out the fact that there could be a principle of procession and the term of procession. The very fact of procession presupposes that there is the principle and the term, otherwise there would be no procession. Non-diversity rules out the fact that the principle and the term are two distinct substances, two different subsisting supposita of essence. Procession in God, by the very fact that it is inward, involves only one single subsisting supposita of the divine essence, God. It occurs in One God; the principle and term of the processions are in this One God.

The supreme unity and simplicity of God excludes every kind of plurality of absolute things but not plurality of relations; because relations are predicated relatively and thus relations do not import composition in that of which they are predicated...

            There is only One God. This One God knows himself and loves himself perfectly. If he does not know and love himself, he is not God. In knowing and loving himself, there are two processions in Him. In knowing himself, an intelligible operation, there is the procession of the Word (His Conception/Knowledge of Himself). In loving Himself, an operation of the will, there is the procession of love (His love of Himself). Owing to the perfection of God, the Word (God’s conception of Himself) is perfectly God, God from God. Just as God is His own Love, God from God. Thus, in God subsists the principle of His Knowledge, His Self-Knowledge and His Self-Love. These are the three persons in God, known as Father, Son and Holy Spirit respectively.

            There is an order of the principle of procession to the term of procession. Since relation is that whereby one refers to another, we can speak of two opposite relations in each of the processions in God. There is the relation of the person proceeding from the principle and the relation of the principle Himself. The relation of the principle of the procession of the Word is called paternity; and the relation of the one proceeding from the principle is called filiation. The relation of the principle of this procession is called spiration; and the relation of the person proceeding is called procession.

The Difficulty of Predicating Persons of God in Speaking of Distinctions in God

            A difficulty arises concerning the meaning of the word Person in God. Names belonging to the essence of God cannot be predicated plurally for there is only one suppositum of the divine essence. Only names which express relation can be predicated plurally. However, the word Person does not seem to express relation, rather it seems to express the individuals of a nature; it seems to belong to the essence of God. Since person is predicated plurally of the Three, how do we explain this without injury to the simplicity of God which permits only one suppositum of the divine essence. The expression three persons seems to suggest that there are three supposita of the divine essence. Remember our definition of person above as an individual subsistent of a rational nature. From this definition, a divine person would seem to be an individual subsistent of the divine essence. How then do we explain three persons without negating the fact that there can only be one suppositum of the divine essence?

The divine simplicity requires that in God essence is the same as "suppositum," which in intellectual substances is nothing else than person. But a difficulty seems to arise from the fact that while the divine persons are multiplied, the essence nevertheless retains its unity.

            In addressing this difficulty, Aquinas explains that it is one thing to ask the meaning of the word Person in general and another to ask the meaning of person as applied to God. The definition above is the definition of person in general; here person signifies the individual substance of a rational figure. This individual is in itself undivided but is distinct from others. Person in any nature signifies what is distinct in that nature. In human nature, it signifies this flesh, these bones and this soul, which are the individuating principles of man. Distinction in human nature is by possessing a particular distinct body and soul. In the definition of person in general, the essential feature is that it must be a distinct individual in the respective rational nature. However, what this distinction consists in differs from nature to nature. What it is in human nature is different from what it is in the divine nature. “Distinction in God is only by relation of origin, and relation in God is not as an accident in a subject, but is the divine essence itself, and so it is subsistent, for the divine essence subsists.” Thus, a person in God refers to a subsisting real relation in the divine essence. Each such relation is a hypostasis (a subsisting individual), although that which subsists in the divine nature is the divine nature itself. The persons are several realities subsistent in the divine nature. There is the reality of Father, Son and Holy Spirit. But these realities are both of and in one essence, one being, God.

            In man, relation is only possible by one suppositum referring to another suppositum. One man is considered father in relation to another man who is son. In one man, there cannot be father and son in relation to one and the same man, without reference to another. In contrast, relation in God does not signify a reference of One God to another God. In God, relation is possible in his one only and single substance due to procession in God.

In creatures relations are accidental, whereas in God they are the divine essence itself. Hence it follows that in God essence is not really distinct from person; and yet that the persons are really distinguished from each other. For person signifies relation as subsisting in the divine nature. But relation as referred to the essence does not differ therefrom really, but only in our way of thinking; while as referred to an opposite relation, it has a real distinction by virtue of that opposition. Thus, there are one essence and three persons.

There cannot be a distinction of "suppositum" in creatures by means of relations, but only by essential principles; because in creatures, relations are not subsistent. But in God relations are subsistent, and so by reason of the opposition between them they distinguish the "supposita"; and yet the essence is not distinguished, because the relations themselves are not distinguished from each other so far as they are identified with the essence.

By procession in God, paternity and filiation refers to two real relations and hence to two real persons (Father and Son) in one God. There is another subsisting relation “procession” which is the third person. Spiration is not a subsisting relation distinct from the Father and the Son.

Although there are four relations in God, one of them, spiration, is not separated from the person of the Father and of the Son, but belongs to both; thus, although it is a relation, it is not called a property, because it does not belong to only one person; nor is it a personal relation--i.e. constituting a person.

The Seeming Poverty of the concept Person for God

            Aquinas goes on to defend the use of this word Person for God and, more so, for its usage in the plural...

Thus it is true to say that the name "person" signifies relation directly, and the essence indirectly; not, however, the relation as such, but as expressed by way of a hypostasis. So likewise it signifies directly the essence, and indirectly the relation, inasmuch as the essence is the same as the hypostasis: while in God the hypostasis is expressed as distinct by the relation: and thus relation, as such, enters into the notion of the person indirectly.

Aquinas argues that the word Person in God signifies properly relations in God. Thus, it is possible to speak of the simplicity of God and three persons in God, for the simplicity of God does not rule out the possibility of relations in God. Thus, the poverty of the term “Person” comes from our imposing what it signifies in human nature on the divine nature. If we consider what the term means in itself, the difficulty of predicating it of God disappears. The three persons are distinguished by relation (relationship of reference, relation of origin), not by divine attributes or missions. The attributes are predicated absolutely.

The absolute properties in God, such as goodness and wisdom, are not mutually opposed; neither are they really distinguished from each other. Thus, although they subsist, they are not several subsistent realities, i.e. several persons ... On the other hand, the relative properties in God subsist and are really distinguished from each other. Hence the plurality of such properties suffices for the plurality of persons in God.

We could speak of One Suppositum of God and Three Supposita in God. In these two ways, suppositum does not mean exactly the same thing. In the One suppositum of God, we are talking of the suppositum/subject of the divine essence and this can only be one. In the Three Supposita in God, we are talking of the supposita/subjects of the subsisting real relations in God and these must be Three. There are three supposita of the relations.

Divine things are named by us after the way of created things; and since created natures are individualized by matter which is the subject of the specific nature, it follows that individuals are called "subjects," "supposita," or "hypostases." So the divine persons are named "supposita" or "hypostases," but not as if there really existed any real "supposition" or "subjection."

God is One with reference to his substance, his essence. God is three with reference to his real relations and his real relations are due to his essence. His relation is not an accident but His very essence. Thus, God is in essence also three as well as One but with different references. God is One; the frame of reference is God’s essence. God is Three; the frame of reference is His Relations.

            In all, Person is not given to signify the individual on the part of the nature, but the subsistent reality in that nature. The divine persons subsist distinctly from others in the divine nature. There is no plurality of the Divine Substance. There is only One Divine Substance, but there is plurality in this one substance. There is only one Divine Substance, One God. But in this one divine substance, there are several subsisting relations. These several subsisting relations are designated persons. Individuality in God is spoken of in terms of distinction of the subject of a subsistent real relations (in the divine nature) which are incommunicable. The persons are to be understood as subsisting real relations. In God Himself, there are subsisting real relations, which we call persons. The several persons are the several subsisting relations really distinct from each other in the divine essence.

Father, Son and Spirit are only “relatively” distinct; that is, in their distinction they should not be conceived as constituted by something which would mean a distinction previous to their mutual relations and serving as their foundation. For such a distinction, previous to the relations as such, would add something to the one divinity and thus do away with its absolute infinity and unity.

Conclusion

            Aquinas was aware of the seeming ambiguity of the concept person. However, he explained the concept stripping it of all of its ambiguity before predicating it of God. If Aquinas is properly understood, the difficulty arising from the predication of person of God would be abated, though the mystery would remain.

            From Aquinas, it is clear that it is impossible to say “three persons, one man”, except if by man, we mean human nature. However, when we say “three persons, one God”, we do not only mean one divine nature only but also one suppositum of the divine nature. Thus, if it were possible to have more than one individual substance of God, each of them would be three persons each; the distinction of persons in God flows from his essence. It is the very essence of God to be three persons in One divine substance. God is a three-personal one, a triune personal being. The Father, Son, and Holy Spirit are not three species of one essence. We must always be on our guard against any tritheistic, modalistic or subordinationalistic understanding, or even materialistic understanding positing that they are three parts of One God. God is not material and he is not composite.