The Blessed Trinity

Introduction

Icon of the Blessed Trinity (Ruvlin)The Trinity is the central mystery of the Christian faith. The term describes the inner life of God, who is an eternal communion of Persons and a Family whose life is love. In more descriptive language, the Church describes the Trinity in the following words:

We firmly believe and confess without reservation that there is only one true God, eternal, infinite and unchangeable, incomprehensible, almighty and ineffable, the Father and the Son and the Holy Spirit; three persons indeed, but one essence, substance or nature entirely simple. (CCC 202)

Frank Sheed describes the Trinity in its barest outline as such:

  1. In the one divine nature, there are three persons, the Father, the Son, and the Holy Spirit.
  2. No one of the persons is either of the others, each is wholly himself.
  3. The Father is God, the Son is God, the Holy Spirit is God.
  4. They are not three Gods but one God. (Frank Sheed, Theology for Beginners, p. 27)

Not surprisingly, this mystery is so puzzling that it has often been the central stumbling block for many to understand the Christian faith throughout 2,000 years of Christian history. Many would agree with Voltaire, who wrote in his Dictionnaire Philosophique:

  • "That nothing is more contrary to strict reason than what is taught among Christians about the Trinity of persons in a single divine essence, the second of which was begotten by the first, and the third of which proceeds from the two others.
  • That this unintelligible doctrine is nowhere found in scripture...
  • That to maintain... that there are several distinct "persons" in the Divine Essence, and that it is not the Eternal who is the only True God, but that the Son and the Holy Ghost must be added to them, is to introduce the crudest and most dangerous error into the church of Jesus Christ, since it manifestly encourages polytheism.
  • That it implies a contradiction to say that there is only one God and that nevertheless there are three "persons", each of which is truly God.
  • That this distinction, one essence and three persons, was never in scripture..."

Voltaire is right that the word "Trinity" does not appear in the Bible. His assertion that the doctrine of the triune God and the distinction of one essence and three persons are not to be found in Scripture, however, is quite wrong. In this article, we will examine the presence of the Blessed Trinity in the Bible, beginning with the Tanakh (the Old Testament), and then moving on to the New Testament. In the third section, we will add some selected quotes from the Church Fathers to document how faith in the Trinity was grasped in the early Church.

It goes without saying that we can only scratch the surface here in introducing the mystery of the Trinity, about which volumes upon volumes have been written. Yet the fact that we call the Trinity "a mystery" does not mean that it is something completely illogical and incomprehensible - and we had better not even try to understand it. A mystery is not a self-contradiction, but rather something that in fact can be known and understood, but only partly and dimly, and only because God has chosen to reveal it to us. As the Catechism of the Catholic Church tells us:

The Trinity is a mystery of faith in the strict sense, one of the mysteries that are hidden in God, which can never be known unless they are revealed by God. To be sure, God has left traces of his Trinitarian being in his work of creation and in his Revelation throughout the Old Testament. But his inmost Being as Holy Trinity is a mystery that is inaccessible to reason alone or even to Israel's faith before the Incarnation of God's Son and the sending of the Holy Spirit. (CCC 237)

One important question follows from this paragraph: if the Trinity is God's very essence, and He seriously cares that we know about it, then why has He not told us up front? Why has He not introduced Himself to us clearly from the beginning, rather than merely leaving vague "traces of his Trinitarian being in his work of creation and in his Revelation throughout the Old Testament"? St. Gregory Nazianzen, a Church Father of the fourth century, provides the answer:

The Old Testament has manifested the Father clearly, the Son only dimly. The New Testament has revealed the Son and implied the divinity of the Spirit. Today the Spirit lives amongst us and makes himself more clearly known. It would actually have been dangerous openly to proclaim the Son while the divinity of the Father was not fully acknowledged, and then, before the divinity of the Son was accepted, to add as it were the extra burden of the Holy Spirit... It was more fitting that by adding a little at a time and, as David says, by ascending from glory to glory, the splendour of the Trinity should shine forth progressively. (Gregory Nazianzen, Fifth Theological Oration, 31, 26).

The Puzzle

Jesus is God

We have seen in another article that Jesus, through his words and deeds, made claims to divinity. To put it more bluntly, Jesus claimed to be God - a shocking claim which was nonetheless accepted and affirmed by the New Testament authors and Church Fathers. We will not review these claims here, but do recommend the reader to read or review the article on the divinity of Messiah, as it constitutes the foundation for our current article on the Blessed Trinity.

Jesus is Distinct from the Father

Jesus claimed to be one with God. Yet he also revealed himself as being distinct from God the Father. Jesus called God "my Father"; he prayed to God. And the New Testament authors also distinguish between "God the Father" and "the Lord Jesus Christ":

Every one therefore who shall confess me before men, him will I also confess before my Father who is in heaven. (Mt 10:32)

All things have been delivered to me by my Father; and no one knows the Son except the Father, and no one knows the Father except the Son and any one to whom the Son chooses to reveal him. (Mt 11:27)

My Father, if it is possible, let this cup pass from me; yet, not as I will, but as you will. (Mt 26:39)

And I will pray the Father, and he will give you another Counselor, to be with you for ever. (Jn 14:16)

Grace to you and peace from God our Father and the Lord Jesus Christ. (Rom 1:7)

For there is one God, and there is one mediator between God and men, the man Christ Jesus. (1 Tim 2:5)

An unsolvable puzzle?

At first sight it seems like Voltaire may be right: According to the Tanakh (the Old Testament), there is only one, transcendent God. But Jesus claimed to be God. He also claimed to be distinct from God the Father. How can these contradictory statements possibly be reconciled? If Jesus is God, but not the same person as God the Father, are they then two distinct “gods”? This would of course entirely contradict the most basic principle of the Jewish faith, the oneness of the Creator, as classically formulated by Maimonides: “I believe with complete faith that the Creator, Blessed is His Name, is unique, and there is no uniqueness like His in any way, and that He alone is our God, Who was, Who is, and Who always be” (Maimonides’ 13 Principles, 2).

Let us now see whether we can solve this puzzle.

Part I: The Trinity in the Tanakh (the Old Testament) and in Jewish Sources

God is Spirit

As we have just said, God is transcendent - entirely distinct from creation. He is not physical or corporeal like man. He is spirit and has no body. He is unchanging, infinite, eternal (CCC 42, 212, 300). At the same time, God immanent: He actively upholds and sustains creation at every moment (CCC 300-301). In the words of the psalmist:

Where can I go from Your Spirit? Or where can I flee from Your presence? If I ascend into heaven, You are there; If I make my bed in hell, behold, You are there. (Ps 139:7-8)

One God

The oneness of God is emphatically affirmed in the Old Testament, with the Sh'ma forming the timeless backbone of the Jewish creed:

Hear, O Israel: The Lord our God, the Lord is one! (Deut 6:4)

I am the Lord, and there is no other; there is no God besides Me. (Isa 45:5, also 46:9)

Yet at the same time the oneness of God is not described as an absolutely singular entity. The Hebrew word for one, "echad," is often used in the Hebrew Scriptures to describe a composite unity made up of two or more parts:

And it was evening, and it was morning – one day (yom echad). (Gen 1:5)

Therefore a man shall leave his father and mother and be joined to his wife, and they shall become one flesh (basar echad). (Gen 2:24)

The whole assembly was as one, forty-two thousand three hundred and sixty. (Ez 2:64)

The Plurality of God in the Old Testament

In addition, there are several passages in the Tanakh which portray God as a composite unity. The most common example is found in almost every page of the Bible: the very name for God in Hebrew, "Elohim," is a plural noun which can also be translated as "gods." Other examples are more explicit:

Let us make man in our image, according to our likeness. (Gen 1:26)

Behold, the man has become like one of us. (Gen 3:22)

And the Lord said: …Come, let us go down and confuse their language… (Gen 11:6-7)

God caused me to wander from my father’s house… (Gen 20:13) [In the original Hebrew, the verb "caused me to wander" (התעו, hit’u) is in the plural. This, however, is lost in the translation.]

There is a God who judges (plural) the earth. (Ps 58:12) [Here also the subtlety is lost in the translation. In Hebrew, the verb "judges" is in the plural, literally: "There are Gods who judge the earth" (יש אלוהים שפטים בארץ).

The LORD said to my Lord, ‘Sit at My right hand, till I make Your enemies Your footstool.’ (Ps 110:1)

Remember your creators in the days of your youth. (Eccl 12:1) [In the Hebrew, the word "your creators" is in the plural (בוראיך).]

One God, Three Persons

Other passages seem to portray a number of persons, two or three at the most, within God himself. Notice in the following passages that God is speaking, yet He seems to be speaking about "another" God - and His Spirit:

Thus says the Lord, the King of Israel (1), and his Redeemer the Lord of hosts (2). (Isa 44:6)

Listen to Me, O Jacob, and Israel, My called: I am He, I am the First, I am also the Last… From the time that it was, I (2) was there. And now the Lord God (1) and His Spirit (3) have sent Me (2). (Isa 48:12, 16)

I will dwell in your midst, says the Lord (2)…then you will know that the Lord of hosts (1) has sent Me (2) to you. (Zech 2:10-11)

The Mystery of Three in the Zohar

The medieval Zohar, the most important book of Jewish mysticism, describes the tri-unity of the Godhead in explicit terms: [emphases added]

Come and see the mystery in the word YHWH: there are three degrees, and each degree exists on its own; nevertheless, they are one, and they are united in a way that they cannot be separated one from another. (Zohar, vol. 3, p. 65, Amsterdam edition)

The same one, Holy and Ancient of Days is revealed in three heads, contained in one head, and it is the head that is exalted three times. (Zohar, vol. 3, p. 288)

God is the artist who dwells above… God is the artist below, and this is the Shekhinah on the earth… The God of creation commanded, and immediately the artist worked and did according to his Word. When God was revealed in the world of the separate ones (the angels), the artist said to the Lord of the buildings: ‘Let us make man in our image, according to our likeness.’ (Zohar, Genesis, p. 22)

The three spirits are united in the One. The spirit located below is called "the Holy Spirit." The middle spirit is the central pillar, called "spirit of wisdom and understanding"… The uppermost spirit is hidden in secrecy, and in it exist all holy spirits and all sources of light. (Zohar, Genesis, p. 15)

YHWH, Adonai, and the Shekhinah, they are the Holy One, blessed be He, and the Shekhinah is located between two extremities: YHWH on its right side, and Adonai on its left side. And they are an illuminating vision. But without the Shekhinah the vision will be obscure. In one righteous, the Shekhinah, they are One. (Tikunei haZohar, p. 66)

The "Middle Spirit": the Word of God

These passages from the Zohar portray God as a tri-unity called by different names: YHWH, Adonai, and the Shekhinah; or the uppermost spirit, the middle spirit, and the spirit below (the Holy Spirit).

The "middle spirit" could well be associated with the eternal Word of God, present before creation, described in the Aramaic Targumim. The Targumim are Jewish translations of the Bible into Aramaic that date back to the early centuries of the Christian era. We will now see that several passages which directly refer to God in the Bible refer to the "Word of the Lord" in the Targum. The following verses will be presented in pairs. The first passage is the verse from Scripture, and the second is its Aramaic translation from the Targum:

So God created man in His own image; in the image of God He created him; male and female He created them. (Gen 1:27)

And the Word of the Lord created man in His likeness, in the likeness of the presence of the Lord He created him, the male and his yoke-fellow He created them. (Jerusalem Targum)
And God spoke all these words, saying… (Ex 20:1)

And the Word of the Lord spoke all the excellency of these words saying... (Jerusalem Targum)
Rise up, O LORD! Let Your enemies be scattered. (Num 10:35)

Arise now, O Word of the Lord, in the power of Thy might, and let the adversaries of Thy people be scattered… (Jerusalem Targum)
Israel shall be saved by the LORD with an everlasting salvation… In the LORD all the descendants of Israel shall be justified, and shall glory. (Isa 45:17,25)

Israel shall be saved by the Word of the Lord with an everlasting salvation… in the Word of the Lord all the descendants of Israel shall be justified and shall glory. (Targum Jonathan)

As we have seen in the article on the divinity of the Messiah, God also appears as the "angel of the Lord" in the Old Testament. The angel of the Lord is also called "Metatron" and "Son of God" in the Zohar and other Jewish mystical works. This "Son of God" is plausibly identical with the "Word of the Lord" spoken of in the Targum.

God's Spirit

In addition to the "middle spirit," who is the eternal Word of God, we also encounter God's Spirit - the Holy Spirit - in the Tanakh, who also seems to be somehow distinct from God Himself:

And the Spirit of God was hovering over the face of the waters. (Gen 1:2)

Do not cast me away from Your presence, and do not take Your Holy Spirit from me. (Ps 51:11)

There shall come forth a Rod from the stem of Jesse, and a Branch shall grow out of his roots. The Spirit of the LORD shall rest upon Him, the Spirit of wisdom and understanding, the Spirit of counsel and might, the Spirit of knowledge and of the fear of the LORD. (Isa 11:1-2)

The Spirit of the Lord GOD is upon Me… (Isa 61:1)

In summary, we see that even though God's self-disclosure in the Tanakh primarily reveals and emphasizes His unity, this unity is by no means absolutely singular, but rather a composite unity - and this composite unity is confirmed by later Jewish sources such as the targumim and the Zohar.

Part II: The Trinity in the New Testament

The Old Testament emphasized the unity of God and only hinted at His tri-unity. As Gregory Nazianzen stated it above in our introduction, it was essential that God first clearly established his oneness before he could disclose his tri-unity. Polytheism was common in the ancient world, and the temptation in Israel would have been too great to slip into tri-theism had not God firmly insisted upon his unity for a millenium or two before manifesting Himself as Trinity.

Yet with the coming of the Messiah, God gradually disclosed His Trinitarian nature and the infinite, intimate communion of love that has existed between the three divine persons for all of eternity. We will now examine some of the Trinitarian passages of the New Testament.

One Lord

The New Testament agrees with the Tanakh in affirming that there is only One Lord:

[There is] one Lord, one faith, one baptism; one God and Father of all, who is over all and through all and in all. (Eph 4:5)

But at the same time the Father, the Son, and the Spirit are all called "Lord":

The Father is Lord: "I will be a Father to you…says the Lord Almighty." (2 Cor 6:18)
The Son is Lord: "the coming of our Lord Jesus Christ." (2 Pet 1:16)
The Spirit is Lord: "Now the Lord is the Spirit." (2 Cor 3:17)

Three Divine Persons

All three persons, the Father, the Son, and the Spirit, are called "God":

The Father is God (1):

For He received from God the Father honor and glory… (2 Pet 1:17)

The Son is God (2):

In the beginning was the Word, and the Word was with God, and the Word was God. (Jn 1:1)
And Thomas answered and said to Him, ‘My Lord and my God!’" (Jn 20:28)

The Spirit is God (3):

Ananias, why has Satan filled your heart to lie to the Holy Spirit? …You have not lied to men but to God. (Ac 5:3-4)
Do you not know that you are the temple of God and that the Spirit of God dwells in you? (1 Cor 3:16)

Trinitarian Passages in the New Testament

Go therefore and make disciples of all the nations, baptizing them in the name of the Father (1) and of the Son (2) and of the Holy Spirit (3). (Mt 28:19)

But the Comforter, the Holy Spirit (3), whom the Father (1) will send in My name (2)… (Jn 14:26)

There are diversities of gifts, but the same Spirit (3). There are differences of ministries, but the same Lord (2). And there are diversities of activities, but it is the same God (1) who works all in all. (1 Cor 12:4-6)

The grace of the Lord Jesus Christ (2), and the love of God (1), and the communion of the Holy Spirit (3) be with you all. (2 Cor 13:14)

For through Him (2) we both have access by one Spirit (3) to the Father (1). (Eph 2:18)

For this reason I bow my knees to the Father (1)… that He would grant you…to be strengthened with might through His Spirit (3)… that Christ (2) may dwell in your hearts through faith. (Eph 3:14-17)

How much more shall the blood of Christ (2), who through the eternal Spirit (3) offered Himself without spot to God (1) cleanse your conscience from dead works to serve the living God. (Heb 9:14)

To the pilgrims… elect according to the foreknowledge of God the Father (1), in sanctification of the Spirit (3), for obedience and sprinkling of the blood of Jesus Christ (2). (1 Pet 1:2)

But you, beloved… praying in the Holy Spirit (3), keep yourselves in the love of God (1), looking for the mercy of our Lord Jesus Christ (2) unto eternal life. (Jude 20-21)

The Dogma of the Holy Trinity

These passages reveal the presence of the Trinity in the New Testament, but they do not explain to us how the Trinity "works". Without getting into a complete treatise on the Trinity, we now turn to the Compendium of Catechism of the Catholic Church for a description of the most essential expression of the Blessed Trinity:

48. How does the Church express her trinitarian faith?

The Church expresses her trinitarian faith by professing a belief in the oneness of God in whom there are three Persons: Father, Son, and Holy Spirit. The three divine Persons are only one God because each of them equally possesses the fullness of the one and indivisible divine nature. They are really distinct from each other by reason of the relations which place them in correspondence to each other. The Father generates the Son; the Son is generated by the Father; the Holy Spirit proceeds from the Father and the Son.

It’s important to note that the terms “generates” and “generated” here do not mean that the Father “created” the Son, or “gave birth” to Him in a human sense. The Father was not originally alone, and then later “created” or “begot” the Son. The Son did not come into existence “later” than the Father; He is not “younger” than the Father (this would really be polytheism). Rather, the Son is “eternally begotten” by the Father and eternally receives His divine nature from the Father. The Son is the Father’s eternal Word, Idea, or self-expression. Father and Son are like thinker and idea: distinct, but not separate, always existing alongside the other and in perfect communion with one another.

And so the Son did not begin to exist when Jesus was conceived in the womb of the Virgin Mary some 2,000 years ago. The divine Son existed eternally; but He took on our human nature and became man 2,000 years ago.

The more comprehensive Catechism of the Catholic Church expands upon this understanding of the Trinity:

253 The Trinity is One. We do not confess three Gods, but one God in three persons, the "consubstantial Trinity". The divine persons do not share the one divinity among themselves but each of them is God whole and entire: "The Father is that which the Son is, the Son that which the Father is, the Father and the Son that which the Holy Spirit is, i.e. by nature one God."

254 The divine persons are really distinct from one another. "God is one but not solitary." "Father", "Son", "Holy Spirit" are not simply names designating modalities of the divine being [such as, for example, water, ice, and steam are three forms of the same substance], for they are really distinct from one another: "He is not the Father who is the Son, nor is the Son he who is the Father, nor is the Holy Spirit he who is the Father or the Son." They are distinct from one another in their relations of origin: "It is the Father who generates, the Son who is begotten, and the Holy Spirit who proceeds." The divine Unity is Triune.

255 The divine persons are relative to one another. Because it does not divide the divine unity, the real distinction of the persons from one another resides solely in the relationships which relate them to one another: In the relational names of the persons the Father is related to the Son, the Son to the Father, and the Holy Spirit to both. While they are called three persons in view of their relations, we believe in one nature or substance... Because of that unity the Father is wholly in the Son and wholly in the Holy Spirit; the Son is wholly in the Father and wholly in the Holy Spirit; the Holy Spirit is wholly in the Father and wholly in the Son.

An Illustration

All this makes for pretty complex theology. Thankfully, there is a simpler way to explain the Trinity. Though this is a classical explanation going back to St. Augustine (early 5th century), the following formulation is borrowed from Frank Sheed's masterful book Theology and Sanity:

God, as person, knows and loves. Because He is infinite, His knowledge and love are infinite. Because He is infinite, His knowledge and love are simply Himself. God's infinite knowledge is the Second Person of the Trinity, the Son. God's infinite love is the Third Person, the Holy Spirit. The Second Person, therefore, proceeds from the First by way of knowledge. The Third Person proceeds by way of love.

The Second Person: The Word and the Son

In the beginning was the Word, and the Word was with God, and the Word was God. (Jn 1:1)

In Frank Sheed's words:

An idea is, so far as we make it so, the mental double or image of the object we are contemplating; it expresses as much of that object as we can manage to get into it. Because of the limitation of our powers, the idea we form is never the perfect double or image, never totally expresses the object, in plain words is never totally adequate. But if God does, as we know from Himself that He does, generate an idea of Himself, this idea must be totally adequate, in no way less than the Being of which it is the Idea, lacking nothing that that Being has. The Idea must contain all the perfection of the Being of which it is the Idea. There can be nothing in the Thinker that is not in His Thought of Himself, otherwise the Thinker would be thinking of Himself inadequately, which is impossible for the Infinite. Thus the Idea, the Word that God generates, is Infinite, Eternal, living, a Person, equal in all things to Him who generates It - Someone as He is, conscious of Himself as he is, God as He is. (Frank Sheed, Theology and Sanity, pg 104)

It also helps to reflect upon the two main titles that describe the Second Person of the Trinity: God the Son and God the Word.

Jesus is God the Son: A son is like in nature to the father. So God the Son, like the Father, is infinite, omnipotent, eternal. Jesus is also God’s Word: God is pure spirit, so His word is like a thought or an idea. God knows himself. When God thinks of himself, this thought must be perfect, because God is perfect, so whatever is in the Father must be in this idea of himself: the "image of the invisible God." (Col 1:15)

The Third Person

Between the two infinite persons of the Father and the Son, there is an infinite love. Since in their mutual love they give everything they have, then the love between them is perfect, so that love produces an eternal person as well, the Holy Spirit:

The First Person knows Himself; His act of knowing Himself produces and Idea, a Word; and this Idea, this Word, is the Second Person. The First Person and the Second combine in an act of love - love of one another, love of the glory of the Godhead which is their own; and just as the act of knowing produces an Idea within the Divine Nature, the act of loving produces a state of Lovingness within the Divine Nature. Into this Lovingness, Father and Son pour all that They have and all the They are, with no diminution, nothing held back. Thus this Lovingness within the Godhead is utterly equal to the Father and the Son, for They have poured Their all into it. There is nothing They have which their Lovingness does not have. Thus Their Lovingness too is Infinite, Eternal, Living, Someone, a Person, God. Observe that here again we are still within the Divine Nature. For love is wholly within the nature of the lover. But this love wholly contains the Divine Nature, for God puts the whole of Himself into love. (Frank Sheed, Theology and Sanity, pg 106)

The Work of the Trinity

The inner working of the Trinity is interesting, you may say, but what has it got to do with us? In fact, the Trinity has everything to do with us. For the Trinity, God's life of love, is the eternal home to which we are called. God freely wills to communicate to us the glory of his blessed life. Such is the eternal plan of his loving kindness: "He destined us in love to be his sons," "conformed to the image of His Son," through "the spirit of sonship" (Eph 1:4-5; Rom 8:15, 29). God’s plan unfolds in the work of creation, the whole history of salvation after the fall, and the missions of the Son and the Spirit which are continued in the mission of the Church. The whole divine economy is the common work of the three divine Persons. Yet each Person has a unique role: the Father is Creator and Provider. The Son is Savior and Redeemer. The Spirit is Sanctifier, Guide, and Guarantor. (CCC 257-59)

The following passages describe the common work of the persons of the Trinity in the New Testament:

In Creation:

Father: "In the beginning God created the heavens and the earth." (Gen 1:1)
Son: "All things were made through Him, and without Him nothing was made that was made." (Jn 1:3)
Spirit: "And the Spirit of God was hovering over the face of the waters." (Gen 1:2)

At Jesus’ Baptism:

Father: "And suddenly a voice came from heaven, saying, ‘This is my beloved Son, in whom I am well pleased." (Mt 3:17)
Son: "Jesus came up immediately from the water." (Mt 3:16)
Spirit: "and He saw the Spirit of God descending like a dove and lighting upon Him." (Mt 3:16)

At Jesus' Resurrection:

Father: "Jesus of Nazareth…whom God raised up, having loosed the pains of death…" (Acts 2:22-24)
Son: "Destroy this temple, and in three days I will raise it up." (Jn 2:19)
Spirit: "But if the Spirit of Him who raised Christ from the dead dwells in you, He who raised Christ from the dead will also give life to your mortal bodies through His Spirit who dwells in you." (Rom 8:11)

Working in the life of the Christian:

Father: "If anyone loves Me, he will keep My word; and My Father will love him, and We will come to him and make Our home with him." (Jn 14:23)
Son: "I will not leave you orphans; I will come to you." (Jn 14:18)
Spirit: "the Spirit of truth…you know Him, for He dwells with you and will be in you." (Jn 14:17)

In the Communication of the Divine Life:

Father: "I bow my knees to the Father of our Lord Jesus Christ…that He would grant you…that you may be filled with all the fullness of God." (Eph 3:14, 19)
Son: "that Christ may dwell in your hearts through faith." (Eph 3:17)
Spirit: "that He would grant you…to be strengthened with might through His Spirit in the inner man." (Eph 3:16)

In the Resurrection of the Believer:

Father: "For as the Father raises the dead and gives life to them…" (Jn 5:21)
Son: "everyone who sees the Son and believes in Him may have everlasting life; and I will raise him up at the last day." (Jn 6:40)
Spirit: "But if the Spirit of Him who raised Christ from the dead dwells in you, He who raised Christ from the dead will also give life to your mortal bodies through His Spirit who dwells in you." (Rom 8:11)

God's Image and Likeness: Called to Share in God's Life

Let Us make man in Our image, according to Our likeness… So God created man in His own image; in the image of God He created him; male and female He created them. (Gen 1:26-27)

The Trinitarian God created us in His own image and likeness. He desires to make himself known and to share His life with us (CCC 257, 260) so we may share in his truth, beauty and goodness (CCC 41, 319). Being in the image of God, man is capable of self-knowledge, of self-possession and of freely giving himself and entering into communion with other persons (CCC 357) - in other words, of imitating the Trinity's life-giving love. This is our ultimate calling: to become capable of loving as God loves us, and to imitate the life-giving love which is the very nature of God, who is an eternal exchange of love within Himself. Our participation in God’s trinitarian life is made possible especially in the Church's liturgy and sacraments, whereby we partake of God's life of grace. The sacraments are efficacious signs of grace by which God's divine, trinitarian life is dispensed to us (CCC 1131).

Part III: The Trinity in Patristic writings

Source for this section: Catholic Answers

We include in this section a number of quotes from the early Church Fathers testifying to their belief in the Trinitarian God, in accordance with the passages from the Tanakh and the New Testament which we have seen above.

The Didache

After the foregoing instructions, baptize in the name of the Father, and of the Son, and of the Holy Spirit, in living [running] water. . . . If you have neither, pour water three times on the head, in the name of the Father, and of the Son, and of the Holy Spirit (Didache 7:1 [A.D. 70]).

Ignatius of Antioch

[T]o the Church at Ephesus in Asia . . . chosen through true suffering by the will of the Father in Jesus Christ our God (Letter to the Ephesians 1 [A.D. 110]).
For our God, Jesus Christ, was conceived by Mary in accord with God’s plan: of the seed of David, it is true, but also of the Holy Spirit (ibid., 18:2).

Justin Martyr

We will prove that we worship him reasonably; for we have learned that he is the Son of the true God himself, that he holds a second place, and the Spirit of prophecy a third. For this they accuse us of madness, saying that we attribute to a crucified man a place second to the unchangeable and eternal God, the Creator of all things; but they are ignorant of the mystery which lies therein (First Apology 13:5–6 [A.D. 151]).

Theophilus of Antioch

It is the attribute of God, of the most high and almighty and of the living God, not only to be everywhere, but also to see and hear all; for he can in no way be contained in a place. . . . The three days before the luminaries were created are types of the Trinity: God, his Word, and his Wisdom (To Autolycus 2:15 [A.D. 181]).

Irenaeus of Lyons

For the Church, although dispersed throughout the whole world even to the ends of the earth, has received from the apostles and from their disciples the faith in one God, the Father Almighty . . . and in one Jesus Christ, the Son of God, who became flesh for our salvation; and in the Holy Spirit (Against Heresies 1:10:1 [A.D. 189]).

Tertullian

We do indeed believe that there is only one God, but we believe that under this dispensation, or, as we say, oikonomia, there is also a Son of this one only God, his Word, who proceeded from him and through whom all things were made and without whom nothing was made. . . . We believe he was sent down by the Father, in accord with his own promise, the Holy Spirit, the Paraclete, the sanctifier of the faith of those who believe in the Father and the Son, and in the Holy Spirit. . . . This rule of faith has been present since the beginning of the gospel, before even the earlier heretics (Against Praxeas 2 [A.D. 216]).

And at the same time the mystery of the oikonomia is safeguarded, for the unity is distributed in a Trinity. Placed in order, the three are the Father, Son, and Spirit. They are three, however, not in condition, but in degree; not in being, but in form; not in power, but in kind; of one being, however, and one condition and one power, because he is one God of whom degrees and forms and kinds are taken into account in the name of the Father, and of the Son, and of the Holy Spirit (ibid.).

Keep always in mind the rule of faith which I profess and by which I bear witness that the Father and the Son and the Spirit are inseparable from each other, and then you will understand what is meant by it. Observe now that I say the Father is other [distinct], the Son is other, and the Spirit is other. This statement is wrongly understood by every uneducated or perversely disposed individual, as if it meant diversity and implied by that diversity a separation of Father, Son, and Holy Spirit (ibid., 9).

Thus the connection of the Father in the Son, and of the Son in the Paraclete, produces three coherent persons, who are yet distinct one from another. These three are, one essence, not one person, as it is said, ‘I and my Father are one’ [John 10:30], in respect of unity of being not singularity of number (ibid., 25).

Origen

For we do not hold that which the heretics imagine: that some part of the being of God was converted into the Son, or that the Son was procreated by the Father from non-existent substances, that is, from a being outside himself, so that there was a time when he [the Son] did not exist (The Fundamental Doctrines 4:4:1 [A.D. 225]).

No, rejecting every suggestion of corporeality, we hold that the Word and the Wisdom was begotten out of the invisible and incorporeal God, without anything corporal being acted upon . . . the expression which we employ, however that there was never a time when he did not exist is to be taken with a certain allowance. For these very words ‘when’ and ‘never’ are terms of temporal significance, while whatever is said of the Father, the Son, and the Holy Spirit, is to be understood as transcending all time, all ages (ibid.).

Pope Dionysius

Next, then, I may properly turn to those who divide and cut apart and destroy the most sacred proclamation of the Church of God, making of it [the Trinity], as it were, three powers, distinct substances, and three godheads. . . . [Some heretics] proclaim that there are in some way three gods, when they divide the sacred unity into three substances foreign to each other and completely separate (Letter to Dionysius of Alexandria 1 [A.D. 262]).

Therefore, the divine Trinity must be gathered up and brought together in one, a summit, as it were, I mean the omnipotent God of the universe. . . . It is blasphemy, then, and not a common one but the worst, to say that the Son is in any way a handiwork [creature]. . . . But if the Son came into being [was created], there was a time when these attributes did not exist; and, consequently, there was a time when God was without them, which is utterly absurd (ibid., 1–2).
Neither, then, may we divide into three godheads the wonderful and divine unity. . . . Rather, we must believe in God, the Father Almighty; and in Christ Jesus, his Son; and in the Holy Spirit; and that the Word is united to the God of the universe. ‘For,’ he says, ‘The Father and I are one,’ and ‘I am in the Father, and the Father in me’ (ibid., 3).

Gregory the Wonderworker

There is one God. . . . There is a perfect Trinity, in glory and eternity and sovereignty, neither divided nor estranged. Wherefore there is nothing either created or in servitude in the Trinity; nor anything superinduced, as if at some former period it was non-existent, and at some later period it was introduced. And thus neither was the Son ever wanting to the Father, nor the Spirit to the Son; but without variation and without change, the same Trinity abides ever (Declaration of Faith [A.D. 265]).

St. Patrick of Ireland

I bind to myself today the strong power of an invocation of the Trinity—the faith of the Trinity in unity, the Creator of the universe (The Breastplate of St. Patrick 1 [A.D. 447]).

[T]here is no other God, nor has there been heretofore, nor will there be hereafter, except God the Father unbegotten, without beginning, from whom is all beginning, upholding all things, as we say, and his Son Jesus Christ, whom we likewise to confess to have always been with the Father—before the world’s beginning. . . . Jesus Christ is the Lord and God in whom we believe . . . and who has poured out on us abundantly the Holy Spirit . . . whom we confess and adore as one God in the Trinity of the sacred Name (Confession of St. Patrick 4 [A.D. 452]).

St. Augustine

All the Catholic interpreters of the divine books of the Old and New Testaments whom I have been able to read, who wrote before me about the Trinity, which is God, intended to teach in accord with the Scriptures that the Father and the Son and the Holy Spirit are of one and the same substance constituting a divine unity with an inseparable equality; and therefore there are not three gods but one God, although the Father begot the Son, and therefore he who is the Son is not the Father; and the Holy Spirit is neither the Father nor the Son but only the Spirit of the Father and of the Son, himself, too, coequal to the Father and to the Son and belonging to the unity of the Trinity (The Trinity 1:4:7 [A.D. 408]).