Confessing Mystery and Talking about the Trinity

The Holy Trinity is the core confession of the Christian faith that lies behind all the biblical content believers confess to be true. It is only by God’s kind condescension in revealing himself that we know him as Trinity. “It is,” as Thomas Aquinas puts it, “impossible to attain to the knowledge of the Trinity by natural reason … by natural reason we can know what belongs to the unity of the essence, but not what belongs to the distinction of the persons”(a). Apart from divine revelation, adequate knowledge of the Trinity is not had, and so eternal life would not be enjoyed by God’s creatures. However, God the Trinity has revealed himself as he is: “No one has ever seen God; the only begotten God [μονογενὴς θεὸς; monogenēs theos(b)], who is at the Father’s side, he has made him known” (John 1:18); “we have received not the spirit of the world, but the Spirit who is from God, that we might understand the things freely given us by God” (1 Cor 2:12). Nonetheless, that God has faithfully revealed himself as he is—as Father, Son, and Holy Spirit—does not mean that our knowledge of him is exhaustive or comprehensive. The doctrine of the Holy Trinity remains mysterious.

Such a confession of “mystery” aligns well with the Christian tradition. Take, for example, post-Reformation theologian, Francis Turretin: “In the Christian religion there are two questions above all others which are difficult. The first concerns the unity of the three persons in the one essence of the Trinity; the other concerns the union of the two natures in the one person in the incarnation”(c). In much earlier circles, one of the Cappadocian church fathers, Gregory of Nazianzus, writes, “To know God is hard, to describe him impossible … mentally to grasp so great a matter is utterly beyond real possibility”(d). So why would we say anything at all about such sacred teaching and reality beyond our intellectual grasp?

Among the numerous reasons to speak about the Trinity (and there really are numerous reasons), space limits me to discuss only one here: the doctrine of the Trinity “pervades”(e) every component of the Christian confession of faith from beginning to end (f). Herman Bavinck says, “The confession of the Trinity is the heartbeat of the Christian religion”(g). He adds, “For the church, the doctrine of the Trinity was the dogma and hence the mystery par excellence. The essence of Christianity … could only be maintained, the church believed, if it was grounded in the ontological Trinity”(h).

The doctrine of the Trinity is not only the “heartbeat” and “essence of Christianity,” but it also acts, as it were, a sort of formal entryway in the Christian faith. In this regard, Scott Swain connects baptism—the entrance rite of Christianity—to the Trinity(i). Jesus himself commissions his disciples, saying, “Go therefore 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). In other words, the formal entrance into Christianity is a rite that involves a trinitarian formula—there is one singular name (τὸ ὄνομα; to onoma), and this singular name is of three persons: Father, Son, and Spirit(j)—wherein we begin “to ‘put on’ the reality signified and sealed to us through baptism in God’s triune name,” namely, that “In baptism the God who is Father, Son, and Spirit signifies and seals to us that he is our Father, through union with the Son, by the indwelling of the Spirit and that we are God’s sons and daughters, fellow heirs with Christ of an eternal kingdom”(k). Put simply, on account of the baptism formula ordained by our Lord Jesus himself, the Trinity is part of the formal Christian basics. 

If this is true, pastors and teachers should not shy away from teaching about the Trinity despite its immense difficulty. That the Trinity is “mystery” does caution what we say about and how far we go in our speech about God, but that does not require us to be completely silent about the doctrine. If (1) the Trinity is the “heartbeat” and “essence of Christianity,” as Bavinck says it is, and (2) if the trinitarian formula is engrained in the entrance rite of Christianity, and (3) if, as Calvin writes, “The final goal of the blessed life, moreover, rests in the knowledge of God”(l), then talking about the Trinity is both joyful and necessary for the Christian life. 

Additionally, we might say something briefly about why talking about the Trinity is worthwhile. We can learn from two prominent figures from the Christian tradition who wrote seminal pieces on the Trinity: Augustine and Thomas Aquinas.

First, in his seminal work, On the Trinity, Augustine famously wrote: “where we are seeking the unity of the three, of Father and Son and Holy Spirit … [there is] nowhere else a mistake more dangerous, or the search more laborious, or discovery more advantageous”(m).

Second, Thomas Aquinas has likewise famously written on the benefits and necessity of speaking about the Trinity, which in one sense elaborates on Augustine’s more general statement:

"There are two reasons why the knowledge of the divine persons was necessary for us. It was necessary for the right idea of creation. The fact of saying that God made all things by His Word excludes the error of those who say that God produced things by necessity. When we say that in Him there is a procession of love, we show that God produced creatures not because He needed them, nor because of any other extrinsic reason, but on account of the love of His own goodness … In another way, and chiefly, that we may think rightly concerning the salvation of the human race, accomplished by the Incarnate Son, and by the gift of the Holy Spirit."(n)

To close, let us recall and enjoy Paul’s trinitarian benediction to the church of Corinth: “The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all” (2 Cor 13:14).


a. Thomas Aquinas, Summa theologiae Ia.32.1 resp.
b. For an understanding of this term, see Charles Lee Irons, “A Lexical Defense of the Johannine ‘Only Begotten,’” in Retrieving Eternal Generation, eds. Fred Sanders and Scott R. Swain.
c. Francis Turretin, Institutes of Elenctic Theology, XIII.xi.1.
d. Gregory of Nazianzus, Oration 28.4 in On God and Christ.
e. I thank Matt Crutchmer for this terminology.
f. John Webster saw this especially well. See John Webster, God Without Measure: Working Papers in Christian Theology, vol. 1, God and the Works of God.
g. Herman Bavinck, Reformed Dogmatics: Abridged in One Volume, 227.
h. Bavinck, RDA, 230.
i. See Scott R. Swain, The Trinity: An Introduction, 16–17, 27–28.
j. See Swain, The Trinity, 30–31.
k. Swain, The Trinity, 17.
l. John Calvin, Institutes of the Christian Religion I.v.1.
m. Augustine, De Trinitate (On the Trinity), I.5.
n. Aquinas, ST Ia.32.1 ad. 3.