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11 Things to Know about the Doctrine of the Trinity

Categories Theology Systematic Theology Online Courses

To contemplate the Trinity is to lift up your heart and to “set your mind on the things above” (Col. 3:2).

It’s easy to turn doctrinal discussions into strictly intellectual affairs, but as Dr. Fred Sanders teaches in The Triune God course, we need to do so “in a way that enlists the reader’s strict and holy attention for what is essentially a spiritual exercise.”

Any discussion of trinitarian doctrine is an attempt to more deeply understand the character and nature of God.

If we’re interested in discovering (and maintaining) an orthodox understanding of the Trinity, there are some principles we need to understand.

These 11 things you need to know about the doctrine of the Trinity are adapted from his course:

1. The revelation of the Trinity comes with the revelation of the gospel.

The doctrine of the Trinity is need-to-know information that we didn’t need to know with any clarity until, as Paul puts it:

“When the set time had fully come, God sent his Son, born of a woman, born under the law, to redeem those under the law, that we might receive adoption to sonship. Because you are his sons, God sent the Spirit of his Son into our hearts, the Spirit who calls out, ‘Abba, Father.’”
—Galatians 4:4–6

God published both the revelation of the gospel and the revelation of the Trinity same time, in the same ways: more obscurely and by way of anticipation under the old covenant, more luminously and by way of fulfillment under the new.

The question of whether the Trinity is revealed in the Old Testament runs parallel to the question of whether the Gospel was.

In both cases, Trinity and gospel, we must account for two factors:

  1. The consistency of God’s entire work of salvation
  2. The newness in “the revelation of the mystery that was kept secret for long ages” (Rom. 16:25) “which was not made known to the sons of men in other generations as it has now been revealed . . .” (Eph. 3:5).

Learn more in The Triune God online course.

2. The revelation of the Trinity accompanies salvation.

We make statements in the doctrine of the Trinity that would be true of God even if we didn’t exist or if the incarnation had never occurred. But what we know about the Trinity always accompanies salvation, and always flourishes in the context of teaching about salvation. This is why the doctrine of the Trinity has been the quintessential catechising doctrine throughout church history.

Even though it can be stated propositionally and in the form of information, the doctrine of the Trinity was not given primarily as information. Rather, this knowledge came along with the carrying out of God’s work of salvation.

God saves, and further, wants the saved to “understand the things freely given us by God” (1 Cor. 2:12). God did not hand down statements regarding the Trinity, but extended his arm to save, an action that by design brought with it knowledge of the one doing the saving.

As B. B. Warfield wrote, “The revelation of the Trinity was incidental to, and the inevitable effect of, the accomplishment of redemption.” (B. B. Warfield, “The Biblical Doctrine of the Trinity,” in Biblical and Theological Studies)

The doctrine of the Trinity is not mainly for apologetics or for opposing heretics (although that’s been an important element of the doctrine); it’s mainly for the purpose of teaching Christians what they believe about God on the basis of being saved by that God.

3. The revelation of the Trinity is revelation of God’s own heart.

It’s hard not to use more emotional language here. As Thomas Goodwin, says, “The gospel reveals the deep things of God.”

When God makes himself known to us and saves us, what he reveals is something from the fundamental depths of who he is.

Theology, broadly considered, is knowledge of God and of all things in God; “all things” are accounted for by a great many doctrines. But the doctrine of the Trinity is theology proper—the knowledge of God.

Its focus is not on those aspects of the divine nature that are knowable by the things created or of God in relation to things outside of him; those things are spoken of in Scripture substance-wise, according to God’s one nature. But the doctrine of the Trinity is a statement about God’s interior life, requiring statements relation-wise, internal to the divine being, describing the Father and the Son and the Spirit as they stand toward each other.

Prepositions will be decisive here: “That true and absolute and perfect doctrine, which forms our faith, is the confession of God from God and God in God” (Hilary of Poitiers, On the Trinity).

If we’re able to say that the Holy Spirit is God or that Jesus is God, we’re able to say that what is made known to us in the Son and the Spirit is about the very heart of God.

4. The revelation of the Trinity must be self-revelation.

The way that God made himself known was not declarative. He didn’t tell us, “I am Father, Son, and Spirit.” He actually sent the Son and the Spirit so that they were here among us, revealing themselves by making themselves present.

This knowledge cannot be delegated or delivered by proxy. As Hilary of Poitiers said, “Since then we are to discourse of the things of God, let us assume that God has full knowledge of Himself, and bow with humble reverence to His words. For He Whom we can only know through His own utterances is the fitting witness concerning Himself” (On the Trinity).

5. The revelation of the Trinity came when the Son and the Spirit came in person.

As was said in the last point, the doctrine of the Trinity wasn’t shouted over the ramparts of heaven. “But when the fullness of time had come, God sent forth his Son . . . And because you are sons, God has sent the Spirit of his Son into our hearts, crying ‘Abba! Father!’” (Gal. 4:4, 6).

God did not openly proclaim the existence of his Son and Holy Spirit and then send them; but he sent them. God did not announce the Trinity; rather, the Son of the Father showed up, with their Spirit.

“The revelation itself was made not in word but in deed. It was made in the incarnation of God the Son, and the outpouring of God the Holy Spirit” (B. B. Warfield, “Biblical Doctrine of the Trinity).

6. New Testament texts about the Trinity tend to be allusions rather than announcements.

There is never a point in the New Testament when Paul writes to a church, “Now concerning the three persons in the one God, brethren, I would not have you ignorant.” That doesn’t happen because neither Paul nor the other apostles ever announce to the church for the first time that we have received information that God is triune.

The churches exist because the Son and the Spirit were sent on the mission of the Father. The kind of work that Paul and the apostles are doing is alluding to a revelation that they had already received.

The evangelists and apostles write from a background assumption that readers know God the Father because they have met the Son and Holy Spirit. They refer almost offhandedly to this understanding as something already given, not something to be introduced, put in place, or argued for. There is an obliqueness in nearly every sentence on this doctrine in the New Testament.

7. The revelation of the Trinity required words to accompany it.

There is a modern way of looking at the revelation of God that only wants to focus on the revelation in actions and wants to deny that there are revelations in words. Or if there are revelations in words, it’s only minor elements and it couldn’t be something as important as the identity of God.

On the contrary, the Son came preaching and the Spirit came bearing witness. So this revelation of the Trinity happened mainly in history but were accompanied by words that have an inner unity with history.

Since the revelation was made by personal presence rather than by mere verbal announcement, interpreting it is in some ways more like interpreting God’s self-revelation through his mighty acts of deliverance than it is like interpreting God’s self-revelation through spoken oracles. But not exactly like it, because this particular mighty act of God was the mighty act of sending persons who speak.

The Son and the Holy Spirit came preaching and testifying to the truth and reality of their own twofold mission from the Father. Without these words, their personal presences would not have been the luminous truth of the knowledge of God.

If the risen Lord had not said, “Baptize in the name of the Father, the Son, and the Holy Spirit,” the early church would never have had the confidence to count to three in the doctrine of God. Biblical revelation is always through acts and words having an inner unity, or fact plus meaning; in the revelation of the Son, the inner unity of his acts and words is his person.

8. The revelation of the Trinity is the extending of a conversation already happening.

As Jesus and the Spirit came among us speaking, teaching, and bearing witness to the identity of God, they’re bringing into our world the conversation that has been going on within the life of God.

When the Father says to the Son, “You are my beloved Son; with you I am well pleased” (Mark 1:11), this is a conversation happening within God. When the Father says to us, “This is my beloved Son, with whom I am well pleased,” he adds, “Listen to him” (Matthew 17:5). When we obey and listen to the Son, we find he tells us about his Father.

Unlike other doctrines, a leading skill in learning about the Trinity is the skill of overhearing as the Father and Son talk to and about each other in the Spirit. This is especially clear in the New Testament, but if the New Testament is to be believed, it is also characteristic of the Old Testament, where Father and Son were speaking to and about each other in words given by the Spirit to the prophets.

Learn more in The Triune God online course.

9. The revelation of the Trinity occurs across the two Testaments of the canon.

We can identify verses and passages, but what we really know about the Son and the Spirit is that their coming was prophesied.

And as we read the Old Testament witness to the one God promising salvation to his people and then see the arrival of the Son and Spirit in the New Testament, we can say, “The one God kept his promise by sending the Son and the Spirit.”

While the New Testament has a strategic priority as the latest moment in the process of progressive revelation, it actually takes both Testaments together to produce the right expectations and interpretive pressure that lead to recognition of the Trinity.

In particular, the canonical order is to be observed in the way God’s unity is analyzed and developed as internally threefold: the Bible is the story of how the one God reveals that divine unity has the form of the unity of Father, Son, and Holy Spirit.

10. The revelation of the Trinity in Scripture is perfect.

There’s a perfection to God’s Word that’s a larger claim than inspiration or inerrancy. The perfection of God’s Word has the practical implication that when we are arranging trinitarian theology so that it can be taught clearly, we’re not improving on the Bible.

It’s easy to think that the task of theology is to make something useful out of the mess of materials that God gave us in Scripture, or at least to put in logical order what was communicated in historical sequence. We’re not looking at Scripture in a way that communicates, “Wow, I can see what you’re trying to say. It’s too bad you don’t have a trained systematic theologian who could get in here and tidy things up and explain to the world what you’re trying to say.”

Theology can think of itself as synthesizing doctrine from raw materials, so in Trinitarian theology we can get turned around by asking, “Is the Trinity in the Bible?” and meaning, “Can the later synthesis be identified as a legitimate construction from the raw materials given in the Bible?”

Something is backward in such a question. In this doctrine especially, it is better to suppose that Scripture speaks from an achieved synthesis and gives partial expression, here and there, to glimpses of that fullness and coherence. To be specific, what we have in Scripture is rightly ordered, with the emphasis falling in the right places.

One application of this principle is that when a passage of Scripture names the Father and the Son, but then fails to complete the triangle, we should neither pronounce it binitarian nor cram the Holy Spirit into it.

In Trinitarian theology, the Holy Spirit in particular has suffered as much from his overzealous promoters as his underzealous neglectors.

He is fully God and a distinct person. But triangular symmetry is manifestly not a concern, or emphasis, or prominent motif, of Scripture, and we should not belabor it in every subpoint of our doctrine.

11. Systematic theology’s account of the Trinity should serve the revelation of the Trinity in Scripture.

Christian theology should be a humble discipline, pointing from itself back to Scripture as much as possible. It may need to invent new terms, make careful distinctions, and construct conceptual schemas to make sense of the evidence; I’m neither justifying theological laziness nor criticizing scholastic predecessors (who tended to obey this rule more than moderns have).

But a systematic rendering of the Trinity should be careful not to rocket out of the orbit of the biblical content it is designed to explain. It ought to eventually lead back to good reading of the text.

Scott Swain argues that “doctrinal propositions apart from the exegetical arguments that they summarize are at best ambiguous” (Scott R. Swain, The God of the Gospel: Robert Jenson’s Trinitarian Theology), and this is especially true in Trinitarian theology, where the dynamics of the arguments can be so conceptually seductive as to alienate theological affections from Holy Scripture.

Because of what the inspired text is—the words of the Father and the Son speaking in the Spirit—readers may actually come into contact with the triune God in them. The doctrine of the Trinity ought to help open that possibility, not obstruct it.


To learn more, sign up for The Triune God course, taught by Dr. Fred Sanders. Take a look at the free preview:

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