Lesson 10: Three Persons are Subsistent Relations

Most of the prayers in the liturgy of the Church are offered to God the Father, through his Son, Jesus Christ, in the unity of the Holy Spirit. As we have seen in previous lectures, there is only one God, but in God there are three distinct Persons. These remarkable truths about God were revealed to the Apostles by Jesus and eventually were written down in the collection of twenty-seven books that we call the New Testament.

Because of modern psychology, we tend to think of "person" as a center of consciousness -- thinking and willing. That is true, but it does not exhaust the reality of what is meant in theology by a divine Person.

In the last talk we considered the difficult truth that the personal names in the Trinity are relative -- Father, Son and Holy Spirit. Thus, when we say "God" we are referring to the divine essence (nature, substance) which is common to all three Persons. When we say "God the Father" we are referring to a relationship in the divinity which is personal. The same holds for the Son and the Holy Spirit.

According to the famous definition of the sixth century philosopher Boethius, "a person is the individual, incommunicable substance of a rational nature." It is an individual substance that exists completely in itself. Person and nature are related to each other in such a way that the person is the possessor of the nature and the ultimate subject of all being and activity, while the nature is that through which the person is and acts.

If you reflect on yourself for a few moments you will see what I mean. When you say "I think" or "my hand" to what reality do the words "I" and "my" refer? They refer to the owner or possessor of all your activities, namely to YOU or your person.

Through such a reflection we can come to see that there is a distinction between what we mean by "person" and what we mean by "nature." This distinction is now common, but it was discovered by the early Fathers of the Church who tried to get a better understanding of the Blessed Trinity.

As I pointed out previously, in God there are two processions -- thinking and loving -- which give rise to the three mutually opposed relations of fatherhood, sonship and passive spiration: these relations are the three divine Persons.

The fatherhood constitutes the Person of the Father, the sonship constitutes the Person of the Son, and the passive spiration constitutes the Person of the Holy Spirit. But in God "everything is one where there is no distinction by relative opposition." Consequently, even though in God there are three Persons, there is only one consciousness, one thinking and one loving. The three Persons share equally in the internal divine activity because they are all identified with the divine essence. For, if each divine Person possessed his own distinct and different consciousness, there would be three gods, not the one God of Christian revelation. So you will see that in this regard there is an immense difference between a divine Person and a human person.

A person is an individual, incommunicable substance of a rational nature. This definition applies to human beings and angels as well as to God. In God, the internal divine relations are substantial because they are really identical with the divine essence. Because they are mutually opposed, incommunicability belongs to the three relations of fatherhood, sonship and passive spiration (active spiration is common to the Father and the Son). Therefore, only these three relations in God are divine Persons. Thus, St. Thomas Aquinas says that each divine Person is a subsistent, incommunicable, internal divine relation (see Summa Theologica, I, Q. 29, a. 4).

By "subsistent" is meant a reality that exists of itself. Since the three divine personal relations are identified with the divine essence, they are subsistent. They are "incommunicable" in the sense that they are not shared by another.

We have been trying to answer the questions: What are the "three" in God that the New Testament tells us about -- Father, Son and Holy Spirit? Or, How can we talk about them? The Church replies that the three are Persons. The, if one asks: What is a divine Person? The answer is that it is a subsistent relation. That is as far as one can go in trying to penetrate the absolute mystery of the Trinity.

Obviously, it is not necessary to know the theology of the Trinity in order to be saved or to live as a devout Catholic. The heart of the Catholic religion is the love and worship of the Father, through the Son, in the Holy Spirit. Jesus said, "This is eternal life -- to know you, the one true God, and Jesus Christ whom you have sent" (John 17:3). But it can be helpful for many Catholics to know that the Church possesses a highly developed rational explanation of the data of Scripture with regard to the Holy Trinity. For, in having us profess faith in the tri-personal One God, the Church is not asking us to believe in something that is contradictory or opposed to human reason. While the Trinity is an absolute mystery, that is, always beyond our grasp and intellectual reach, it is not opposed to reason.

By a "mystery" is meant something that is hidden, veiled, unknown. In this sense, there are many mysteries of nature, since there are aspects of atoms, molecules and living beings that are not yet known. Thus, science is constantly trying to unravel the "mysteries" of nature. This is not what is meant by mystery in the theological sense since human science by experiments and perseverance can finally unlock the secrets of nature. In other words, natural truths are not beyond the power of human reason.

In Catholic theology a "mystery" of faith is a truth revealed by God which totally surpasses the power of the human mind. Once it has been revealed by God we can know something about it, such as the Holy Trinity, the Incarnation and divine grace, but we could never come to any knowledge of it from our observation or experience. Fr. John A. Hardon, S.J., gives the following definition of mystery in his book Modern Catholic Dictionary (Doubleday, 1980): "MYSTERY. A divinely revealed truth whose very possibility cannot be rationally conceived before it is revealed and, after revelation, whose inner essence cannot be fully understood by the finite mind."

Mysteries in this sense are truths that concern God himself, since he is infinite and absolutely incomprehensible to the created mind. Theologians usually list three mysteries in this category: the Trinity, the Incarnation and divine grace or the supernatural. For, these three have to do with the very being of God. According to Catholic teaching these truths are absolute mysteries. By an absolute mystery is meant a truth that not only surpasses the power of the human intellect in this life, but also will surpass it in the next life in heaven. Thus, it follows that the blessed in heaven do not comprehend the Holy Trinity, that is, they do not fully understand it; for all eternity they can learn more and more about it and never exhaust its knowability. Such a consideration gives a hint of the activity connected with the lives of the saints who see God face to face.

The Catholic Church teaches in Vatican I that "there are two orders of knowledge, distinct not only in origin but also in object. They are distinct in origin, because in one we know by means of natural reason; in the other, by means of divine faith. And they are distinct in object, because in addition to what natural reason can attain, we have proposed to us as objects of belief mysteries that are hidden in God and which, unless divinely revealed, can never be known" (Denzinger 1795).

By natural reason we can come to a knowledge of God as their origin and source (see Rom. 1). But the various perfections of God which are revealed through the contemplation of created things, such as his power, wisdom and goodness, are common the three divine Persons. Therefore, natural reason can know God only in his unity of substance, but not in his trinity of Persons.

Our knowledge of the inner life of God -- the life of Father, Son and Holy Spirit -- must come through revelation by God in history. That took place primarily in Jesus Christ and through his Apostles.

Jesus revealed to us the absolute mysteries of the Holy Trinity, his Incarnation and divine grace. In order to receive this revelation we must be able to understand something about these mysteries. They are revealed to us through human words and human actions. We understand something about them when we accept them in faith, but we do not completely grasp them. In theological language, we do not "comprehend" them because "comprehend" means to understand something completely. By reading the Bible, by prayer and by meditation we can come to a deeper understanding of these mysteries, but we will never exhaust them because they have to do with God himself and he is infinitely exalted above us.

Once we know about the inner life of God we can learn more about it by comparing it with the created things we know. In fact, we have already done that in this series when we considered how the Son proceeds from the Father by way of intellectual generation. But the truth about God always remains obscure because, as St. Paul says, in this life "we walk by faith and not by sight" (2 Cor. 5:6f.).

Finally, it is important to note that the dogma of the Trinity is beyond reason, but not contrary to reason. St. Thomas Aquinas says that human reason of itself cannot show the possibility of the Trinity, but it can show that it is not contradictory, and so it can refute all counter-arguments. The Church in Vatican I said that even though faith is above reason, "yet there can never be any real disagreement between faith and reason, because it is the same God who reveals mysteries and infuses faith and has put the light of reason into the human soul" (Denzinger 1797). Therefore, it is reasonable to believe in the Trinity and to adore the Trinity because God has revealed it "who can neither deceive nor be deceived." So there can be no conflict or disagreement between faith and reason because it is the same God who created the world and reveals mysteries of his own inner life.

Reading Assignment

St. Thomas Aquinas, Summa Theologica I, Q. 29, a. 4; Q. 40, a. 2.

Writing Assignment

Write an essay of two to three pages on one of the following two topics: 

1) Explain why Catholic theology calls the three Persons in the Trinity subsistent divine relations.

2) Explain why the three Persons in one God is not contrary to human reason.


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