Thomas Aquinas writes: “The purpose and the fruit of our whole life is the knowledge of the Trinity in unity” (Commentary on the Sentences, 1, 2, 1). In a way, Thomas is speaking about eternal life, the culmination of our lives, when we understand more clearly the mystery of the Trinity. Yet, even now we can slowly appreciate the actions of the Father, Son and the Holy Spirit in our lives.

An excellent step in this appreciation is reading the New Testament. As we read the various parts of the New Testament attentively, we can recognize a consistent pattern of three subjects acting in divine ways. The New Testament authors simply describe these divine actions in a very natural way without explaining, assuming that the Father acts in this way, the Son acts in this way, the Spirit acts in this way.

A good example is the second reading for today from Paul’s Letter to the Romans, 8:14-17. Paul speaks of our being “led by the Spirit of God.” Someone might assume that Paul means God’s spirit, as if we were to say “the mind of God.” However, Paul indicates that the Spirit is distinct from God the Father: “The Spirit Himself gives witness with our spirit that we are children of God.”

In the New Testament, almost always “God” refers to the Father. Two exceptions are when John states that “the Word was God” (Jn 1:1) and when Thomas exclaims at the sight of Jesus, “My Lord and My God” (Jn 20:28). In the Gospels, Jesus always addresses God as “Father,” with the exception of His cry from the Cross, when He repeats the words of Psalm 22:1, “My God, My God,”

Scholars are sure that Jesus’ name for “Father” was the Aramaic form, Abba. Paul uses Abba in this passage from Romans. Scholars conclude that Paul would have been unlikely to use an Aramaic word when writing to the Christians of Rome, many of whom were Gentiles, unless these Christians were accustomed to Jesus’ name for the Father.

Jesus speaks of Himself as “the Son” and of God as “My Father.” He also speaks to the people of “your Father,” implying a difference.

This difference appears in this passage from Romans. Paul affirms that we call out Abba in “a spirit of adoption. We are said to be “heirs with Christ,” implying that Christ is the heir by nature.

There are two striking references in today’s Gospel, coming at the close of Matthew’s Gospel, Mt 28:16-20. Just before Jesus ascends into heaven, the eleven disciples “fell down in homage” before Him. Never before had the disciples given Jesus such homage during the time of His ministry. At the beginning of the Gospel, the Wise Men fell down in homage of the Infant Jesus, foretelling the future homage of the disciples.

Jesus instructs the disciples to make disciples of all nations: “Baptize them in the name of the Father, and of the Son, and of the Holy Spirit.” The three names are joined together, indicating their equality. The Spirit would not have been included with the Father and Son if He were simply a power of God. Jesus assures the disciples of His continued presence, “I am with you always.”

Thomas Aquinas was convinced that, although we might be able to reason to the existence of God from creation, we cannot prove that God is Three: “It is impossible to come to the knowledge of the Trinity of divine Persons through natural reason… by natural reason we can know of God only what characterizes Him necessarily as the source of all beings…” (1a. 32, 1).

Thomas cautions against relying on natural proofs or unconvincing arguments to prove the Trinity, lest one “becomes a laughing stock for the unbelievers, who think we rely on such arguments and believe because of them” (1a. 32, 1).

Augustine had proposed some analogies, such as an example of human intellect, will, and memory, which are three powers that are one but distinct. Thomas insists, “The analogy from our intellect also does not establish anything about God conclusively because it is not in the same sense that we speak of intellect in God and in us” (1a. 32, 1, ad 2).

Thomas does present an analogy of the Trinity with our minds, realizing that it is a weak comparison. Thomas affirms that our intellect and our will are the two powers of our souls. The intellect has the ability to know and the will has the ability to love. When a person knows in words, those words are within the person and have a likeness to the person. When the person speaks those words, the words reveal the person, yet the words still remain within the speaker. In a certain limited way, the words that remain within our minds, even when spoken, reflect the Son within the Father.

Thomas states: “Whenever anyone understands because of his very act of understanding, something comes forth within him, which is the concept of the known thing proceeding from his awareness of it. It is this concept which an utterance signifies; we call it ‘the word in the heart,’ signified by the spoken word (1a. 27, 1).

In a similar way, God conceives a Word, which is united with God and reflects God so much that this Word is His Image, having His nature so closely that it is His Son: “The Word comes forth with the same nature” (1a. 27, 2).  This Word reveals Him and all creation comes forth through the Word.

With regard to creatures, His Word not only expresses what is in creatures but causes these creatures to be. Thus, God’s plan for the being of all things is in the Word (1a. 34, 3).

The generation of the Word corresponds to the action of the intellect. But there is also the action of the will. In a certain sense, what one loves is within the one loving, just as a thing known is within the one who knows.

Thomas explains, “The coming forth in the intellect bears a likeness but the coming forth in the will is an urge or motion towards something. Thus what proceeds is not a likeness or a Son but a breathing of spirit, a living motion or impulse as when someone loves is driven by love (1a. 27, 4).

In the Trinity the Son, is known in the understanding and the love in the divine will is the Spirit. “Love” is the name for the Spirit (1a. 37, 1).

Thomas explains the Spirit as the bond of Love of Father and Son:

The Holy Spirit is called the bond between Father and Son in that He is love. The reason: because the Father loves the Son and the Son loves the Father by the one single Love, the name of the Holy Spirit as He is love implies the co-relationship between Father and Son as between lover and beloved. But from the fact that Father and Son love each other mutually, their mutual love, the Holy Spirit, necessarily proceeds from both (1a. 37, 1 ad 3).

Thomas explains that we are created through the Son and we are loved through the Spirit:

By the Holy Spirit the Father loves not only the Son but Himself and us as well…. Just as the Father utters Himself and every creature by the Word He begets, as the Word begotten completely expresses the Father and every creature, so He loves Himself and every creature by the Holy Spirit, as the Holy Spirit proceeds as Love…. The Word and Love proceeding include, a secondary reference to creation, as the divine truth and goodness are the grounds for God knowing and loving any creature” (1a. 37, 2 ad 3).

Thomas was well aware that this analogy from the human intellect and will was only a weak reflection of the Trinity. Nevertheless, it does give us some perspective since we speak of the Son as the “Word” and of the Spirit as “Love.”

Denis Vincent Wiseman, O.P.

References to Thomas Aquinas’ Summa Theologiae, first name the part or the Summa. Thomas’ treatise on the Trinity is found in the first part. Secondly, the number of the question is given, followed by the article. If he is responding to an objection, the Latin ad, meaning “to” is used, and then the number of the objection.

When we love, there is a movement towards another person within our minds. This movement remains within us yet also reaches to the other person. In a similar way, the Holy Spirit is God’s love.

“The soul is made like to God by grace. Hence for a divine Person to be sent to anyone by grace, there must be a likening of the soul to the divine Person Who is sent, by some gift of grace. Because the Holy Spirit is Love, the soul is assimilated to the Holy Ghost by the gift of charity: hence the mission of the Holy Spirit is according to the mode of charity. Whereas the Son is the Word, not any sort of word, but one that breaths forth Love. Hence Augustine says: ‘The Word we speak is knowledge with love’ (De Trinitate, 9,10). Thus the Son is sent not in accordance with every and any kind of intellectual perfection, but according to the intellectual illumination, which breaks forth into the affection of love, as is said, “Everyone who has heard from the Father and has learned comes to Me’ (Jn 6:45), and the Psalm, ‘In my meditation, a fire shall come forth’ (Ps 38:4). Augustine plainly say, ‘The Son is sent, whenever He is known and perceived by anyone’ (De Trinitate, 4, 20). Now perception involves a certain experiential knowledge and this is properly called wisdom, as it were, a sweet knowledge…” (1a. 43, 5 ad 2; First Part, question 43, article 5, reply to the 2nd objection).

St. Thomas Aquinas, Summa Theologiae, Vol. I trans. English Dominicans (New York: Benzinger Brothers, 1947), 222-223.