The Splendor of the Three-in-One God: The Necessity and Mystery of the Trinity

©1999 Modern Reformation All Rights Reserved. For permission to reprint or re-post contact Modern Reformation

Hear, O Israel, the Lord our God, the Lord is one!” In contrast to the polytheistic religions of her neighbors, Israel was made deeply conscious of the fact that there is only one God (hence, the term, “monotheism”). The monotheistic doctrine of God is at the headwaters of the Christian faith, but it is the doctrine of the Trinity which makes our doctrine of God distinctively Christian. Islam, one of the world’s fastest growing religions, is monotheistic, but rejects entirely the doctrine of the Trinity as unreasonable. Jewish critics have long regarded the doctrine of the Trinity as polytheistic. Clearly the doctrine of the Trinity is a stumbling block to vast numbers of people, but without it we are no longer Christians. The Trinity is among those doctrines by which heresy (as distinguished from error) against the “catholic, undoubted Christian faith” is properly judged (Heidelberg Catechism, Q. 22). Since the fourth century AD, the agreement among orthodox, catholic Christians on the essentials of the doctrine of the Trinity has greatly outdistanced agreement on many other doctrines (e.g., the doctrine of salvation). 1

Given the centrality to our faith of our teaching about the Trinity, it is profoundly ironic that for most believers this doctrine is practically disposable. In my experience, most North American evangelical Christians when asked to state the doctrine of the Trinity (if they can do it at all) will almost always give a heretical answer. The most common heresy among Western Christians has been “modalism,” which is the notion that God is not really one God in three persons, but rather only appears to be three persons. This is what we often teach in our Sunday Schools by way of the illustrations we use which imply that God wears a series of masks (first Father, then Son, then Spirit) or takes different forms under different conditions (e.g., water in solid, liquid, and gas forms). 2

The Christian view of God is, as the Athanasian Creed teaches, that:

…we worship one God in Trinity, and Trinity in Unity; neither confounding the Persons, nor dividing the Substance. For there is one Person of the Father, another of the Son, and another of the Holy Ghost. But the Godhead of the Father, of the Son, and of the Holy Ghost, is all one, the Glory equal, the Majesty co-eternal.

As this creed continues, “the Father is Almighty, the Son Almighty, and the Holy Ghost Almighty. And yet they are not three Almighties, but one Almighty.” In biblical, creedal, and Christian teaching, God is one substance (Deut. 6:4). Whatever it is which makes the Father to be God, is that which makes the Son and the Spirit to be God: “Such as the Father is, such is the Son, and such is the Holy Ghost (Athanasian Creed).

At the same time, tri-personality is also essential to the Deity: “For there is one Person of the Father, another of the Son, and another of the Holy Ghost” (Athanasian Creed). It is possible to conceive of a god who is unipersonal, but the history of theology shows that any such god would necessarily be impersonal and so transcendent as to be unknowable, which is practical atheism. 3 If we lose God’s tri-personality we forfeit our Christology. We believe that Jesus Christ is God the Son in the flesh, that he is of the same substance as God the Father and God the Spirit. We would also forfeit our Pneumatology (that is, the doctrine of the Holy Spirit) since we also believe that God the Spirit is of the same substance as the Father and the Son. If this is so (and without these truths one cannot be a Christian!), then God must be triune. As the Athanasian Creed puts it: “Unity in Trinity and the Trinity in Unity is to be worshipped.”

How this can be is a mystery, but it is a necessary mystery. It is necessary because “we are compelled by the Christian verity” to confess this doctrine. It is necessary because: “Whosoever will be saved, before all things it is necessary that he hold the catholic Faith. Which Faith except everyone do keep whole and undefiled, without doubt he shall perish everlastingly” (Athanasian Creed). It is a necessary doctrine because our very destiny is at stake, not merely fine points of doctrine.

The Necessity of the Trinity

The way one reads the Bible is intimately related to the God one finds revealed there. Christians, being Trinitarian, read the Bible as a unity. That is, because God is one, the Scriptures are one. If God is revealed to be triune in the New Testament we should expect to find him so revealed in the Old Testament. God’s Word itself recommends this hermeneutic: 1 Peter 1:10-12 teaches us that the same Holy Spirit who inspired Moses and the prophets also inspired the apostles as they interpreted the Law and the Prophets for us.

It also means, as John 1:1 teaches us, that the Son has always been God’s Word. He did not become the Word only in the incarnation, but rather he was the Word “in the beginning.” More than that, he was “with” God the Father, which means that he has always been personally distinct from the Father. At the same time the Word “is God” which means that God the Son and God the Father are, as the Nicene Creed states, “of the same substance” (consubstantial). Thus, the Apostle John teaches us not to read the Son into the Old Testament, but to refuse to read him out of it.

Hence, when we consider the fundamental Israelite confession about God, “Hear O Israel, Yahweh our God, Yahweh is one” (Deut. 6:4), we understand that this unity not only permits but entails tri-personality. Indeed, read from the perspective of the New Testament–how else can a Christian read Scripture?–the Old Testament is rich with Trinitarian revelation. The New Testament turns to several places in the Old Testament for its doctrine of the Trinity. Psalm 110 is cited more than any other Old Testament passage (see Matt. 22:44; 26:64; Mark 12:36; 14:62; Luke 20:42-43; 22:69; Acts 2:34-35; Heb. 1:13; 5:6, 10; 7:17, 21). The psalm speaks of the accession and rule of a Davidic Priest-King. The New Testament, however, focuses consistently on the doctrinal teaching of the psalm and, therefore, regards it as a promise of the ascension and inter-adventual reign of Christ. In that case, the primary reference of the psalm is not (as Peter reminds us in Acts 2:34-35) to David, but to the intra-Trinitarian relations between the Father and the Son and the outworking of those relations in redemptive history.

A second strand of Trinitarian revelation in the Old Testament is the revelation of the Son in the history of redemption in the person of the Angel of the Lord (Malak Yahweh). When the Angel of the Lord appeared he was treated not as a mere heavenly representative of God, but as God himself; he did not reject worship, but accepted it as only God can. (Typically it is only after one has had an encounter with the Angel of the Lord that one realizes that, in fact, it was no mere angel but God himself; see Gen. 16:9-13; 22:11-18; 32:28-30; Ex. 3:2-6; Judges 6:11-14, 22; 13:22.) Both Augustine and Calvin interpreted these manifestations as wonderfully cryptic revelations of God the Son in a pre-incarnate state. 4

John 1:1-3 teaches that when Genesis 1:1 says, “In the beginning God created the heavens and the earth,” we should understand that creation occurred through the agency of God the Son and that his work was essential to the act of creation because the Creator God is triune.

The work of redemption was also a Trinitarian work. Think, for instance, of the deliverance of God’s people from Egypt. On the principle that the God who revealed himself to Israel is triune, and that the Son has always been the Word (God’s authoritative self-revelation), we should consider that it was God the Son who met Moses in the burning bush, and at the top of Mount Sinai: “No one has ever seen God; God the only begotten who is in the bosom of the Father, this one has revealed him” (John 1:18). Jesus declared, “Anyone who has seen me, has seen the Father” (John 14:9). The writer to the Hebrews teaches that Christ is not only the “radiance of the glory” but the “exact manifestation” of the “divine being” (hypostasis), “sustaining all things by his powerful word” (Heb. 1:3).

Hebrews 12:18-24 contrasts Mount Sinai with that mountain to which we have come. In so doing, however, it also tells us how we should think about the God who revealed his “hindmost quarters” to Moses. The mountain to which Moses came was covered in darkness, fire, gloom, and storm. In the New Covenant believers have come, however, to thousands of angels, to “the church of the firstborn, whose names are written in heaven. You have come to God, the judge of all men, to the spirits of righteous men made perfect, to Jesus the mediator of a new covenant, and to the sprinkled blood that speaks a better word than the blood of Abel” (Heb. 12:23-24). Notice how the writer to the Hebrews uses a series of parallel expressions to drive home the same point: “church of the firstborn” (i.e., the risen Christ), “God, the judge of all men” who is “Jesus the mediator of a better covenant.” It was the Son who was revealed awesomely at the top of Sinai, who met with the elders, before whom they ate and drank, whom they “saw and did not die” (Ex. 24:9-11), and it is the Son with whom we have to do today.

There is significant evidence that God the Spirit was also active in creation. The New International Version is right to spell Spirit with the capital “S” in Genesis 1:2. The “Spirit of God was hovering over the waters.” That such work is proper to the Spirit is suggested in 1 Peter 4:14 which uses the same image to describe the Spirit’s relations to the New Covenant temple people. By the analogy of Scripture we understand that it was God the Spirit who guided us through the wilderness. The pillar of divine presence, surrounds and protects God’s people, hovering over his creation and new creation, indwelling and sanctifying, as he ever has. 5

God the Father was also active in creation, speaking the Word, present in the redemption of Israel in the person of the Son, by the power of the Spirit. Who else could have passed over Israel for the sake of the blood of the lamb, but God the Father? One has only to think of how the Father provided earthly manna for his people and how he gave that ultimate manna which gives eternal life to all who eat by faith (John 6:31-33). Certainly one sees wonderful evidence of his providence throughout the Hebrew Scriptures. At each turn the Father was meeting our needs, with drink from the rock and food from heaven (Num. 20:11, 1 Cor 10:1-4). All this establishes not only that God revealed personal distinctions in the Old Testament, but that he revealed himself as tri-personal.

The New Covenant Scriptures make explicit what was implicit in the Old Covenant. We may begin with our Lord, himself a Trinitarian theologian. His conception of himself and of his relations to the Father and the Spirit was unreservedly Trinitarian. This is not surprising given that he was himself a member of the triune Godhead, God the co-eternal, eternally begotten Son incarnate. We have already reviewed Jesus’ revelation of the personal distinction between himself and the Father. He also made clear that God the Spirit has his proper work drawing sinners to the Son; “the Spirit blows where he will” and without the work of the Spirit no one is able to see the Kingdom of God (John 3:8).

Christ’s Trinitarian consciousness is clearly evident in his command to baptize in the triune name of God. “Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit…” (Matt. 28:19). Notice that Jesus said, “in the name.² This is a most significant expression in Scripture. Out of the burning bush God the Son revealed the divine name to Moses: I AM. God’s name is who he is in himself, and also who he is in relation to us, the self-existent one. Thus, Herman Bavinck was right to say that, in this passage, Jesus drew together all the Trinitarian revelation of God in Scripture. 6

Paul was equally explicit about God’s tri-personality in the benediction contained in 2 Corinthians 13:14 in which he named each of the Trinitarian persons: “May the grace of the Lord Jesus Christ, and the love of God, and the fellowship of the Holy Spirit be with you all.² (This expression is doubtless linked to the Aaronic benediction of Numbers 6:24-26.) This was Paul’s consistent language about God. Frequently he used the noun “God” to refer to the Father (e.g., Rom. 1:1, 7, 8; 8:14-17; 15:5-6; 1 Cor 1:3; 8:6; 11:3; 2 Cor 1:2; Gal. 1:3; Eph. 1:2, 17; 4:6; 5:20). He refers to the Son as “Christ” and to the third triune person as the “Spirit.” Read this way, his epistles are replete with allusions to the Trinity.

It is no wonder then that the earliest Fathers of the Christian church developed the biblical Trinitarianism almost immediately. This teaching was crystallized in the great ecumenical creeds: The Apostles’ Creed, the Nicene Creed (325 AD), the Athanasian Creed (381-421 AD) and the Chalcedonian Definition (451 AD). 7

Against the Arians, Athanasius (c. 293-373), an Alexandrian archdeacon, defended stoutly the doctrine of the eternal generation of the Son. When Scripture says “only begotten God,” it means that the Son has always been begotten of the Father (see John 1:18). There has never been a point (remember we’re speaking of eternity) when the Son was not. The Son has always been the Son and the Father has always been his Father. This eternal begottenness of the Son does not mean, however, that the Son is a creature. Because he is the same substance (homoousios) as the Father and the Spirit, he was also uncreated.

The biblical and Christian doctrine of the Trinity is a necessary mystery to the faith so that without it, there would be no faith. It is necessary primarily because the Scriptures teach it. Because it is a biblical doctrine, the creeds teach it and for the same reasons our theologians have taught it. Despite all the attempts by students to investigate it and despite all the attempts by critics to level it, the doctrine of the Trinity remains a glorious mystery.

The Mystery of the Trinity

“So the Father is God, the Son is God, and the Holy Ghost is God. And yet they are not three Gods, but one God” (Athanasian Creed). How can God be truly one and also three distinct, co-eternal, subsistences or persons is a mystery; and yet we are bound to say that he is. To confess these truths is to commit oneself to a great and glorious mystery–that is, something which is necessarily true but which transcends our ability to explain fully. 8

In this case, then, we must repudiate the root of the Arian heresy: rationalism, the notion that one should believe only that which one can comprehend entirely. With Athanasius, we know that if “there was when the Son was not,” the Son could never be a Savior. He also knew that we can confess Jesus to be “very God of very God” only if God is triune; otherwise we are polytheists. “So we are forbidden by the catholic religion, to say, There be three Gods, or three Lords” (Athanasian Creed).

As trinitarians we also acknowledge that it is possible to apprehend revealed truths about God and to develop them, but it is not possible to comprehend him in our formulae. Therefore, it is impossible to remove mystery from the Trinity and remain Christian. At the same time, it is also evident that Christianity is a theological religion. That is to say, it is not sufficient to quote Scripture in the face of heresy, but rather we are morally obligated not only to read Scripture carefully, but also to assemble its truths, to make good and necessary deductions from scriptural truth to edify God’s people, and to array those truths against unbelief.

For example, our Trinitarianism separates us utterly from unbelief. There is no other article of the Christian faith which so alienates unbelievers as our claim that there is one God in three persons. When we come to the doctrine of the Trinity, we Christians realize that we are completely dependent upon God’s Word for saving knowledge of God. Since the patristic-creedal period, perhaps no theologian has meditated on the Trinity more profitably than John Calvin (1509-64). 9 With the breakup of the medieval Church, the sixteenth century was littered with sects including anti-trinitarians. Calvin responded to the Unitarians by defending both God’s essential simplicity (God is one) and his tri-personality or tri-subsistence (Institutes 1.13.2, 6).

He used the term subsistence to distinguish between the divine essence and his tri-personality. These sorts of considerations are sometimes developed under the heading ontological Trinity, i.e., the Trinity regarding God’s being. He reminded us that there are certain attributes which belong to each Trinitarian person which are not shared among the persons of the Trinity. Recognizing these distinctions is part of not “confounding the persons” (Athanasian Creed). These properties unique to each person distinguish (not separate) each person from the others. For example, only the Father is unbegotten. “The Father is made of none, neither created, nor begotten” (Athanasian Creed). The Son, because he is such, is eternally begotten. “The Son is of the Father alone, not made, nor created, but begotten” (Athanasian Creed). Only the Spirit is able to proceed from the Father and the Son. “The Holy Ghost is of the Father and Son, neither made, nor created, nor begotten, but proceeding” (Athanasian Creed). Considered distinctly, however, each divine person can be said to be God “of himself,” i.e., the Father, Son and Spirit subsist of themselves. “And in this Trinity none is afore, or after other; none is greater, or less than another” (Athanasian Creed).

At the same time, Calvin also reminds us of another heading in the doctrine of the Trinity, the economic Trinity. This relates to the outworking of creation and redemption. For example, it belongs to the Son to become incarnate. It belongs to the Father to elect people to faith in Christ. It belongs to the Spirit to draw sinners to Christ and to sanctify them through the Word. Under this heading, we can think of the Father primarily as the Creator. The first articles of the Nicene and Apostles’ Creeds both encourage this sort of thinking. The Son can be said to have voluntarily subordinated himself to the Father, for the sake of redeeming his people, and the Spirit voluntarily subordinates himself to the Father and the Son for the sake of sanctifying his people, as the Nicene and Apostles’ Creeds both teach.

Thinking in these categories does not imply, however, that either the Son or the Spirit became less than they were, otherwise we would be “dividing the persons” (Athanasian Creed). Rather, these distinctions are a part of the administration of salvation, not changes in the divine being.

Both the personal distinctions within the Trinity and the Trinitarian character of God’s works of creation and redemption witness to the fundamental unity in the divine being. They also witness to the eternal fellowship and love which exists within the Trinity. The Greek Fathers spoke of God’s perichoresis or what Francis Turretin called the “mutual intertwining” of the persons of the Deity.10 In this case, we know that the Trinity we worship is no static deity, but rather that there are dynamic relations among the Father, the Son, and the Spirit. It is out of that dynamic, loving fellowship that both creation and redemption have issued.


The doctrine of the Trinity is of the essence of our religion. We cannot and should not think of creation or redemption as anything but Trinitarian operations. This is a duty of the Christian faith. Christianity is more than duty, however. Being drawn to greater wonder and awe before the face of God is one his best gifts. The Trinity reminds one that the Christian religion is not about us, but about God and his glorious grace. The Father to whom we pray is the eternal Father of our Lord Jesus Christ, in whose name we pray, and the Spirit in whose power we pray is of the same substance as the Father and the Son and he is their gift to us to draw us by Christ to the Father.

Since the Trinity is such a necessary mystery, though woefully misunderstood or forgotten in our churches, how can we recover this truth? Three sources have helped me. First, God’s Word is thoroughly Trinitarian and it is the fundamental source of all Christian teaching. Second, it was through meditating on the Nicene and Athanasian Creeds that I began to read Scripture with renewed Trinitarian eyes. Third, the Athanasian and Nicene Creeds also alerted me to the fact that Reformed theology is unreservedly Trinitarian. 11 It structures our theology. Calvin’s Institutes (1559) were laid out along the lines of the Creed. The Heidelberg Catechism (1563) is in three parts, each roughly corresponding to the work of the economic Trinity.

The benefits of reading the Bible in the communion of the saints (e.g., Athanasius, Basil, Calvin) have been revolutionary. Recovering the doctrine of the Trinity has delivered me from a warped conception of God. I have learned again that there is no other God than the God who is one substance in three subsistences (persons); that the Christian is not entitled to think of God in any other way than he has revealed himself (Heidelberg Catechism Q. 25, 96); that with Calvin and before him Gregory of Nazianzus (330-89) we must say, “I cannot think on the one without quickly being encircled by the splendor of the three; nor can I discern the three without being straightaway carried back to the one.” 12 For Gregory, for Calvin, and for us, to think of God as triune is not a second blessing, reserved for the illuminati. Rather, it is how anyone must think of God, for any other god is an idol to be rejected. 13


1 For example, semi-Pelagianism, whether in its Roman or Arminian form is a grave error, but it is not heresy, at least not in the same way as anti-Trinitarianism. It is true, however, that certain modern developments in Roman dogma (e.g., the alleged assumption of the Virgin Mary) threaten seriously the catholicity of their doctrine of God.

2 Some other well-meant but errant illustrations: the egg, forms of gold, apple, the lover, beloved and love and the shamrock. On the dangers of such analogies, see John Calvin, Institutes, 1.13.18. L. Berkhof gives a more favorable view of some analogies. See idem, Systematic Theology (Grand Rapids: Eerdmans, 1939), 90.

3 This is true of Islam. Strictly speaking Allah is not personal. Personal speech about him is mere convention. This is true of most other forms of Unitarianism.

4 See Peter Toon, Our Triune God: A Biblical Portrayal of the Trinity (Wheaton: Victor, 1996), 82-85, 90-92. See also Herman Bavinck, The Doctrine of God, trans. W. Hendriksen (Grand Rapids: Eerdmans, 1955); and Hermann Witsius, The Apostles’ Creed, trans. D. Fraser, 2 vol. (Edinburgh, 1823; [reprint: den Dulk Foundation P&R Publishing, 1993]), especially vol. 1.

5 See Dennis E. Johnson, “Fire in God¹s House: Imagery from Malachi 3 in Peter’s Theology of Suffering (1 Pet. 4:12-19),” Journal of the Evangelical Theological Society 29 (1986), 285-94. See also M. G. Kline, Images of the Spirit (Grand Rapids: Baker, 1980); Bavinck, 255-56, 271-74.

6 Bavinck, 264-66.

7 See Gerald L. Bray, “The Patristic Dogma,” in Peter Toon and James D. Spiceland, eds., One God in Trinity (Westchester: Cornerstone Books), 42-61; idem, “Explaining Christianity to Pagans: The Second Century Apologists,” in Kevin J. Vanhoozer, ed., The Trinity in a Pluralistic Age: Theological Essays on Culture and Religion (Grand Rapids: Eerdmans, 1997). The Chalcedonian Definition was primarily a Christological statement, but it presupposed the creedal doctrine of the Trinity.

8 The great Reformed theologian Francis Turretin spoke of the “adorable mystery” of the Trinity. See F. Turretin, Institutes of Elenctic Theology, 3 vol., trans. by G. M. Giger, ed. by J. T. Dennison, Jr. (Phillipsburg, NJ: P&R Publishing, 1992-1997), 1:3:23.

9 See Calvin, Institutes, 1.13. Also see B. B. Warfield, “Calvin’s Doctrine of the Trinity, The Princeton Theological Review 7 (1909), 553-652, reprint in Calvin and Calvinism (New York, 1931). The latter edition is used here. See also R. S. Clark, “The Catholic-Calvinist Trinitarianism of Caspar Olevian (1536-87),” Westminster Theological Journal 61 (1999): 15-39.

10 Turretin, Institutes, 1:3:23:13.

11. On this point, see Clark, “The Catholic-Calvinist Trinitarianism”; Carl R. Trueman, The Claims of Truth: John Owen¹s Trinitarian Theology (Carlisle, UK: Paternoster, 1998); idem and R. S. Clark, ed., Protestant Scholasticism: Essays in Reassessment (Carlisle, UK: Paternoster, 1999).

12 On Holy Baptism, oration 40.41, cited in Calvin, Institutes, 1.13.17.

13 Witsius, ibid., 1:129, 135.

    Post authored by:

  • R. Scott Clark
    Author Image

    R.Scott Clark is the President of the Heidelberg Reformation Association, the author and editor of, and contributor to several books and the author of many articles. He has taught church history and historical theology since 1997 at Westminster Seminary California. He has also taught at Wheaton College, Reformed Theological Seminary, and Concordia University. He has hosted the Heidelblog since 2007.

    More by R. Scott Clark ›

Subscribe to the Heidelblog today!