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The Doctrine of the Trinity

Explore the Distinctive and Central Doctrine of the Christian Faith

Curated by Fred Zaspel

Course Introduction

If ever there was a doctrine that is distinctive of Christianity it is the doctrine of the Trinity – the teaching that God is one in being and essence yet three in persons, that there is one God and that he subsists in three persons. As Martin Luther summarized it, “We believe the divine majesty to be three distinct persons of one true essence.” It is, in fact, the leading mystery of the Christian faith, and difficult as it is to comprehend, it is a doctrine on which professing Christians of virtually all denominational labels agree – and have agreed since the very beginning.

Nor is it a doctrine of mere isolated importance: it is a doctrine that shapes the whole of the Christian faith and devotion. We Christians revel in the fact that God has saved us, and when we set out to explain what that means we cannot avoid speaking of God as Father, Son, and Spirit – that the Father in grace sent his Son on a mission of rescue, that the Son came and accomplished our redemption, and that the Spirit, being sent by the Father and the Son, has drawn us to Christ, uniting us to him so that we may enjoy, in him, all the benefits of his saving work. Indeed, by the Spirit the Triune God himself has come to indwell us, to make us his, and to secure us for himself in love forever. When we are baptized, we are baptized into the name (note the singular) of the Father, and of the Son, and of the Holy Spirit. When we pray, we pray to the Father in the name of the Son and by the enablement of the Spirit and thereby worship the Triune God. When we sing, we sing praise to the one God who has saved us, and yet when we itemize that saving work we speak distributively of the work of the Father, the Son, and the Spirit. “The grace of our Lord Jesus Christ, and the love of God [the Father], and the fellowship of the Holy Spirit” (2 Cor. 13:14) are “with us” in joyful realization of the saving work of each, together, for us. We praise the Father for sending his Son; we praise the Son for coming to us in his incarnation, life, death, resurrection, ascension, and eventual return; we praise the Spirit for shedding abroad in our hearts this wonderful sense of the love of God for us, causing us to know in experience that we are sons of God in Christ; and we praise the Three in One. Clearly, this doctrine is much more than mere abstract truth of isolated significance.

And yet it is a doctrine that is ultimately impossible to grasp fully. It is, after all, the leading mystery of our faith. And it is here, perhaps more than at any other place, we are reminded that when we come to study and learn about God, we are in over our heads. Here we are brought to realize that God is like no other and that he is beyond the bounds of our finite minds. We may know him truly, for he has revealed himself to us. But we cannot grasp him fully. And so we learn to bow in humble adoration of his greatness and glory.

Here, then, is a doctrine designed to make us worship. Thus, we pursue this study as an end in itself, so that we may worship God more adequately and attribute to him more of the praise he deserves from us. And we pursue this study for our own sakes also, that we may revel more fully and more joyfully in the wonder of who he is and what he has done for us.

“Glory be to the Father, and to the Son, and to the Holy Ghost.”

Four Essential Affirmations

In this section we introduce the doctrine of the Trinity. The biblical teaching on the Trinity embodies four essential affirmations (see the ESV Study Bible for more detail):

  1. There is one and only one true and living God.
  2. This one God eternally exists in three persons—God the Father, God the Son, and God the Holy Spirit.
  3. These three persons are completely equal in attributes, each with the same divine nature.
  4. While each person is fully and completely God, the persons are not identical. The differences among Father, Son, and Holy Spirit are found in the way they relate to one another and the role each plays in accomplishing their unified purpose.

As you begin studying the trinity, the quiz below will help you determine whether your beliefs line up with the historic Christian views of the doctrine.

Now that you have tested your knowledge of the doctrine, the following Scripture passages, videos, articles, and books will help you correct or enhance your understanding of the trinity.

Relevant Scripture

Matthew 11:27; 28:19; 1 Corinthians 8:4–6; 12:4–6; 2 Corinthians 13:14; Ephesians 1:3–14; 4:1–6; 1 Peter 1:1–2

  • R. C. Sproul – Trinity
  • R. C. Sproul – For the Doctrine of the Trinity
  • Gavin Ortlund, Scott Swain, & Ligon Duncan – How is the Trinity Central to the Gospel

Recommended Books
Summary: Reformed Dogmatics (Volume 2), Chapter 6: The Holy Trinity
Summary: What is the Trinity?

The Revelation of the Doctrine of the Trinity

Christian theologians regularly emphasize that the doctrine of the Trinity is something we can know only from Scripture, yet they also point out that God did not reveal himself as triune from the very beginning. We may see hints of it in the Old Testament, but not until the New Testament is this doctrine entirely clear. Moreover, the way the doctrine appears in the New Testament reflects a revelatory act that preceded its writing.

Thus the revelation of God to Israel culminated in the revelation of God coming to save his people. It was not clearly revealed to Israel that this coming of Jehovah to redemption was one with the coming of the anointed King; as it was not clearly revealed to Israel that the anointed King was one with the atoning Servant. It required the fulfilment to weave together all the threads of the great revelation into one marvelous portraiture. But it was clearly revealed to Israel that God was its Saviour, and that he would visit his people in his compassion, and that he would redeem them from all their iniquities. In this hope Israel rested, and by it Israel lived: and resting in and living by it Israel laid its ear to the ground and listened with beating heart for the voice crying, “Prepare ye in the wilderness the way of Jehovah, make level in the desert a highway for our God.” Oh, the pity of it, that when at last the long expected voice went booming out from the water of Jordan, Israel’s ear was holden that it should not hear; and it failed to recognize in the “Behold, the man!” of the Roman governor the “Behold your God” for which it had so long been waiting. But verily it was he who came, as a mighty one, and his arm has ruled for him, and he has fed his flock like a shepherd, and gathered his lambs in his arms, and carried them in his bosom, and gently led those that give suck. And it is his voice and none other, that is crying down the ages, “Look unto me, and be ye saved, all the ends of the earth; for I am God, and there is none else.”  (B. B. Warfield)

  • R. C. Sproul – The Mystery of Trinity (Part 1)
  • Fred Sanders – Hearing Voices: The Trinity Speaking in the Old Testament
  • Fred Sanders – Theology of the Trinity
Audio Lecture Series
  • Sinclair Ferguson – Old Testament Revelation of Trinity (Part 1)Runtime: 46 min<p>1998 Westminster Lectures on Biblical Theology</p>
  • Sinclair Ferguson – Old Testament Revelation of Trinity (Part 2)Runtime: 45 min<p>1998 Westminster Lectures on Biblical Theology</p>
  • Sinclair Ferguson – Old Testament Revelation of Trinity (Part 3)Runtime: 44 min<p>1998 Westminster Lectures on Biblical Theology</p>
  • Sinclair Ferguson – Old Testament Revelation of Trinity (Part 4)Runtime: 44 min<p>1998 Westminster Lectures on Biblical Theology</p>
Additional Reading
B.B. Warfield – God’s Revelation of Himself to Israel

Biblical Essentials on the Trinity

Virtually all Christians acknowledge that there is no single passage of Scripture that is given to defending or explaining the doctrine of the Trinity, as such. Yet Christians of all stripes also agree—indeed, they insist—that Scripture does, in fact, teach this doctrine. Roman Catholic, Eastern Orthodox, and Protestant—all heartily confess the Trinity. So just what are the biblical essentials that make this doctrine so obvious? That is the question we take up in this section.

Though you won’t find the word Trinity in the Bible, the concept is biblical. This doctrine emerges when all of Scripture is surveyed and three essential elements come together. First, there’s only one God. Second, the Father, Son, and Holy Spirit are distinct persons. Third, each of these persons is fully God.

Element #1: From Genesis to Revelation, the Bible clearly affirms monotheism—that there is only one God. Every morning the faithful Jew would repeat a prayer known as the Shema: “Listen, Israel: The Lord our God, the Lord is one” (Dt 6:4). Isaiah also speaks with clarity that there is no God but one (Is 43:10; 44:6; 45:5; see 1Co 8:4). Jesus too affirms this belief when explaining the greatest commandment (Mk 12:29).

Element #2: The Father, Son, and Holy Spirit are clearly distinguished from each other by the way they interact with one other in personal ways. For example, at Jesus’s baptism, as the Holy Spirit descends on the Son, the Father says, “You are my beloved Son; with you I am well-pleased” (Lk 3:22).

Element #3: All three persons of the Trinity are fully God. The Father is repeatedly called God (1Co 8:6; 1Pt 1:3). Paul writes, “Blessed is the God and Father of our Lord Jesus Christ” (Eph 1:3). The Son is called God on numerous occasions (Jn 1:1; Rm 9:5; Ti 2:13–15; Heb 1:8; 2Pt 1:1). For instance, Thomas boldly calls Jesus, “My Lord and my God” (Jn 20:28). Finally, in the inception of the church, Ananias and Sapphira dropped dead after lying to the Holy Spirit since they had “not lied to people but to God” (Acts 5:1–4).

Therefore, if there is only one God, and if the Father, Son, and Holy Spirit are distinct persons, and if all are affirmed to be fully God, then the only explanation that makes sense of all the biblical data is the Trinity. ~ CSB Apologetics Study Bible for Students 

  • R. C. Sproul – The Mystery of Trinity (Part 2)
  • Dennis E. Johnson – The Trinity's Work in Salvation
  • Michael Reeves – A Trinitarian Gospel

On Key New Testament Passages
B. B. Warfield – Matthew 28:19
B. B. Warfield – The Trinity in the Gospel of John
B. B. Warfield – The Trinity in the Epistles
B. B. Warfield – 1 Corinthians 8:4–6

On NT Trinitarian Theology
Sinclair B. Ferguson – The Trinity in the New Testament
Charles Hodge – The Trinity
Herman Bavinck – Father, Son, and Spirit

Summary: The Essential Trinity (Part 1)
Summary: The Forgotten Trinity (cc. 11–12)
Summary: The Holy Trinity (cc. 1–3)

Historical Development of the Doctrine

Believing and confessing that God is Father, Son, and Spirit is one thing. It can be quite another to explain it with precision—and still another to answer all the attending questions. Just what, then, do we mean when we affirm that God is one? And how is this one God three? In what sense is God one? And in what sense is he three? Is each Person fully equal to the others? Or is the Father superior? What is the relation of the three Persons? What is it that makes them distinct … and yet one? Just how do we explain this mystery?

That the New Testament church believed in God as Trinity is reflected on virtually every page of the New Testament, but it fell to the church of the following centuries to put it all together in precise theological statement. And the statement they eventually gave has been enthusiastically embraced by the entire church of all the centuries. It is the development of this doctrine in the teachings of the early church and beyond that occupies our attention in this section.

It is in this intimacy of relation between the doctrines of the Trinity and redemption that the ultimate reason lies why the Christian church could not rest until it had attained a definite and well-compacted doctrine of the Trinity. Nothing else could be accepted as an adequate foundation for the experience of the Christian salvation. Neither the Sabellian nor the Arian construction could meet and satisfy the data of the consciousness of salvation, any more than either could meet and satisfy the data of the Scriptural revelation. The data of the Scriptural revelation might, to be sure, have been left unsatisfied: men might have found a modus vivendi with neglected, or even with perverted Scriptural teaching. But perverted or neglected elements of Christian experience are more clamant in their demands for attention and correction. The dissatisfied Christian consciousness necessarily searched the Scriptures, on the emergence of every new attempt to state the doctrine of the nature and relations of God, to see whether these things were true, and never reached contentment until the Scriptural data were given their consistent formulation in a valid doctrine of the Trinity. Here too the heart of man was restless until it found its rest in the Triune God, the author, procurer and applier of salvation.  ~ B. B. Warfield

  • R. C. Sproul – The Mystery of Trinity (Part 3)
  • R. C. Sproul – The Mystery of Trinity (Part 4)
  • Ryan Reeves – Early Church & Trinity
Additional Downloads
  • DownloadMichael A. G. Haykin – The Brilliance of the RainbowFiletype: .pdf
  • DownloadMichael A. G. Haykin – Glory to the Three EternalFiletype: .pdf
  • DownloadSummary Outline: Oration 31 (On the Deity of the Holy Spirit) by Gregory of NanzianzusFiletype: .pdf
B. B. Warfield – The Development of the Doctrine of the Trinity
Summary: The Holy Trinity (cc. 4–6)

Addressing Specific Issues

Now that we have investigated the biblical teachings concerning the Trinity, and now that we have listened to the discussion of the church in this regard, we are in a position to state the doctrine clearly ourselves and answer attending questions. Just what is meant when we say God is one and three? Just what are the relations of the three Persons? Does the historical revelation of God as triune reflect God he is “in himself”? Do God’s outward works reflect the relations of the three eternally? Is Christ is subordinate to the Father? And if so, is the same true of God the Son eternally? These important questions deserve careful attention. And you have probably noticed already that Christians have a distinct vocabulary when talking about the Trinity. Accepted terminology—a Trinitarian “Grammar”—has developed over the centuries to aid our understanding. These are the kinds of issues we address now in this section as we bring together what we’ve learned so far.

Scripture also gives us insight into the relations between the three persons of the Trinity. God the Father is the Creator, the father of his people, Israel, and supremely the father of his Son, the “Father of our Lord Jesus Christ.” The Father is preeminent in creation and redemption, the first in the divine economy. From this the Arians wrongly infer that the Father alone is God; a claim found nowhere in Scripture. On the contrary, the names given to Christ reveal the immanent relations of the triune God. Thus, Logos points to the one who is able to fully reveal God because from all eternity God communicated himself in all his fullness to him. He is also the Son of God in a metaphysical sense; by nature and from eternity he is elevated above angels and prophets. He is the “firstborn” and “only begotten” as the full image of God, who from all eternity bears a unique relation to the Father. He is not a creature, but is and was and remains God, who is over all, blessed forever. The Spirit is God as the immanent principle of life throughout creation; he is holy because he is God. He is both divine and personal. Finally, as Christ is related to the Father, so the Spirit is related to Christ. As the Son witnesses to and glorifies the Father, so the Spirit witnesses to and glorifies the Son. By the Spirit we have communion with no one less than the Son and the Father themselves. ~ Herman Bavinck

  • R. C. Sproul – The Mystery of Trinity (Part 5)
  • R. C. Sproul – The Mystery of Trinity (Part 6)
Carl R. Trueman – Trinitarianism 101: Evangelical Confusion and Problems
Matthew Y. Emerson – Trinitarian Vocabulary and Grammar

The Trinity & the Christian Life

No one has ever seriously argued the point, but some seem to assume that the doctrine of the Trinity is a doctrine merely abstract, a doctrine for theologians only and a doctrine that has no great bearing on Christian worship, life, and devotion—that there is little of “practical” value to the average Christian. But nothing could be further from the truth. This doctrine, distinctive of Christianity itself, is foundational to and has direct bearing on the way we perceive our faith and our salvation, and it is the shaping factor of Christian worship. Here we explore some of those implications.

To the great One-in-Three,

Eternal praises be,

Hence, evermore!

His sovereign majesty

May we in glory see,

And to eternity

Love and adore!

  • Sinclair Ferguson – The Doctrine of the Trinity Brings Comfort
  • Fred Sanders – Adoption and Prayer in the Trinity
  • D. A. Carson, John Piper, & Tim Keller – Only the Triune God is Love
Summary: Delighting in the Trinity
Summary: The Essential Trinity (Part 2)
Summary: On Communion with God
Excerpt: Father, Son and Spirit (c. 9)
Summary: The Deep Things of God
  • Michael Haykin – Knowing and Adoring the Triune GodRuntime: 53 min

Additional Resources

  • Scott R. Swain – The Trinity
  • Fred Sanders – The Trinity and the Shack
  • DownloadA. A. Hodge – Outlines of TheologyFiletype: .pdf<p>On the Trinity</p>

Additional Summaries

Summary: "To Serapion on the Holy Spirit" by St. Athanasius
  • DownloadOutline: St. Athanasius – On the Incarnation of the WordFiletype: .pdf
Summary: "On the Holy Spirit" by Basil the Great
Summary: The Holy Trinity (cc. 7–20)
Summary: The Quest for the Trinity
Summary: Shared Life