5 Ways the Doctrine of the Trinity Is Surprisingly Practical

doctrine of the trinity

Even the best metaphors fail to capture the complexities of God’s being. In fact, when Christians attempt to explain the Trinity, they often stumble into metaphors that sound suspiciously like the very heresies Trinitarian theology was developed to counteract!

But even if you conquer the intimidating task of explaining the meaning of the Trinity, you may face an even more momentous challenge: demonstrating why it matters.

Pastor and theologian Peter Leithart says that, far from being an abstract theological concept only for the most pedigreed theologians, the doctrine of the Trinity has profound, practical implications. And not just for the way we think about God; the Trinity should affect the way we live the Christian life.

The doctrine of the Trinity . . . is a practical doctrine. It tells us what God is like, it tells us what to be like, it says something about the kind of God we worship and the way God interacts with us and with the world. As we understand more and more what the Bible reveals to us about the Father, Son, and the Holy Spirit, the more practical this doctrine becomes.

Here are five ways the doctrine of the Trinity is surprisingly practical, all drawn from Peter Leithart’s Mobile Ed course on Trinitarian theology and his book Traces of the Trinity.

1. The Trinity distinguishes Christianity from other religions

Why does it make any difference if we say God is Father, Son, and Spirit, instead of just one person—like Allah? In this clip from his Mobile Ed course on Trinitarian theology, Leithart argues that the doctrine of the Trinity underscores the differences between Christianity and other religions.

If we jettison the doctrine of the Trinity, we forfeit one of the key doctrines that distinguishes Christianity from other monotheistic religions. What’s more, we’re left with a conception of divinity that fails to account for one of the most fundamental aspects of God’s being: love.

2. The Trinity enriches our understanding of righteousness

As demonstrated in the clip above, Leithart—like St. Augustine before him—roots the divine attribute of love in the very nature of the Trinity. But he goes on to argue that our understanding of every single attribute of God should be informed by the Trinity:

All the . . . attributes the Bible talks about are attributes of the triune God, and we can reason about all of these attributes in the context of Trinitarian theology. And unless we do, we are missing a large part of what these attributes mean.

For instance, Christians everywhere describe God as eternally righteous. But let’s imagine for a moment that God does not exist as a Trinity. If righteousness is meeting one’s obligations, and If God is only one person—what’s known as a unitarian view of God’s being—how could God be truly righteous? How could God be “righteous” before any other person existed?

Leithart says that no matter how you define it, the very concept of “righteousness” implies the existence of more than one person. A unitary being can’t have obligations. The most you could say is that such a one is “potentially righteous.”

Define righteousness however you like. Define righteousness as faithfulness in relationship. Define righteousness as justice. How can a righteous God be truly righteous, actively righteous, if he is only one person? The righteousness of God is the righteousness of the relationship of Father, Son, and Spirit. They are faithful in those relationships; they are just in those relationships. Those relationships have the characteristic of righteousness. And this is active righteousness; this isn’t simply potential righteousness as a unitarian God would have.

Without the doctrine of the Trinity, we couldn’t claim that God is righteous in any meaningful way.

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3. The Trinity underscores the importance of relationships

In his book Traces of the Trinity, Leithart dives deep into a little-known theological concept called vestigia Trinitatis. Meaning “traces of the Trinity,” vestigia Trinitatis is all about identifying the Trinitarian underpinnings of a universe spoken into existence by a triune God.

In other words, if the Christian God is the creator of the universe, then it follows that there would be traces of the Trinity etched into the substructure of the cosmos—from the intricate complexities of science and mathematics to everyday human interactions.

By analyzing everything from the nature of time to human communication, Leithart follows many theologians before him in concluding:

The Father, Son, and Spirit live in a harmony and love that is a model for human life . . . . Others indwell our lives; therefore we ought to open our lives hospitably to them. We indwell the lives of others; therefore, we ought to see others not as obstacles to our plots and projects but as potential homes in which we can dwell together. A world of mutual [indwelling] implies an ethic of hospitality, welcome, invitation, companionship, centered on a common table.

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4. The Trinity demonstrates the true meaning of holiness

Likewise, our conception of holiness should be undergirded by a Trinitarian framework. To demonstrate this, Leithart first establishes the biblical understanding of holiness.

If we define holiness in biblical terms, holiness has to do with indwelling and possession. God consecrates persons and places and things by coming near to them and indwelling them in glory. God comes into the tabernacle and indwells the tabernacle. He is enthroned above the Cherubim in the most holy place, and he consecrates the tent by His presence. He claims places as his peculiar places by indwelling them in his glory.

Having shown the Bible’s unique take on holiness, Leithart goes on to explore its implications regarding the Trinity.

If that’s what holiness is about, if that’s what holiness means, then a single entity, a single person, a single divine person, cannot be holy. He can’t be holy in the sense that he is separated from everything. He can’t be holy in the sense that he consecrates or is consecrated by another.

But when we think about the Trinity as a holy communion, then we can see that indwelling is essential to their holiness. The Father is holy because he is indwelt by the Spirit and by the Son. The Son is holy because the Holy Spirit indwells Him eternally, the Holy Spirit that comes from the Father. The Spirit is holy because he is indwelt by the Father and the Son. The three persons consecrate each other in a communion of holiness.

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5. The Trinity clarifies the meaning of the “glory of God”

One of the most respected summaries of Christian doctrine, the Westminster Shorter Catechism, asserts “man’s chief end is to glorify God and to enjoy him forever.”

When some Christians hear that, their skin crawls. Doesn’t that make God seem selfish? Is the creator of the universe really that egotistical—really that insecure—that he has to create an entire species to satisfy his hunger for worship?

Leithart is sensitive to this objection—and says that a robust understanding of the Trinity can overcome it.

That objection comes from not recognizing that the God who seeks all glory for himself is not a single entity who is sucking the glory from everything, but a communion of persons, a communion of mutually glorifying persons. Jesus, at the beginning of his high priestly prayer, speaks of the glory with which the Father has glorified him, and he declares his intention to glorify the Father. Within the communion of God, the Father is not seeking glory from the Son; he is glorifying the Son. The Son is not seeking glory for himself, but he is seeking the glory of his Father. And the Spirit is not seeking glory for himself, but he is glorifying the Father and the Son, or he is the glory that glorifies the Father and the Son.

When we think about God as a God who glorifies himself within a Trinitarian context, we can see that there is a mutual glorification going on, and God is not selfish. No person of God is selfish. But within God, there is this humility and self-sacrifice for the sake and for the glory of the other.

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A practical doctrine

The doctrine of the Trinity can be daunting to describe, but its rewards are equally grand. When we glimpse the beauty of this teaching—not in spite of, but because of its rich complexity—its implications stretch before us in ever-widening circles: from the very reason for our existence, to the way we live our lives, to the way we treat one another, and even to the way we relate to other religions and worldviews.

Perhaps most precious of all, the doctrine of the Trinity reveals that woven into the very fabric of the universe is the self-giving love of God.

And what could be more practical than love?


Learn more about the Trinity, the sacraments, and hermeneutics straight from Peter Leithart himself. Learn more about the bundle and get it today!

Written by
Tyler Smith
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  • “Traces of the trinity” and other mined insights here may be very spiritually enriching and philosophically stimulating, but I always wonder about the significance of this doctrine, if not its veracity. It’s not that I don’t believe “trinity.” It’s more that I don’t want to claim something that is not explicitly claimed in the scriptures. For now, I’m content to reside in the reality of this blogpost’s very first line: even the best metaphors can’t explain God.

    • Good thoughts, Brian. I tend to follow the principle from The Westminster Confession of Faith that says, “The whole counsel of God concerning all things necessary for his own glory, man’s salvation, faith and life, is either expressly set down in Scripture, or by good and necessary consequence may be deduced from Scripture: unto which nothing at any time is to be added, whether by new revelations of the Spirit, or traditions of men.”

      I think the Trinity is a “good and necesarry consequence” deduced from Scripture. Thanks for sharing your thoughts!

  • Your first two arguments presupposes a weak, impotent god. My God is almighty. I am sorry, but if I were sitting in your class I would have to stand up and proclaim the same thing. How can you put such restrictions on the Creator and Sustainer? My God could be only One, but He chose to be Three in order that He could interact and redeem you and me. But given even that, I still have problems with your first two arguments because they are based upon narrow, obscure definitions. Are you really trying to argue that a unitarian god could not love those he created? Are you really trying to argue that there is no love nor righteousness possible in a unitarian god? I know my God is Trinitarian and there is no other. But I would never restrict His capability! Not for one minute would do that, not even to say that the gods others worship are false because they are not like mine. There are plenty of other attributes of our God you could focus on to prove your point rather than limiting His capabilities.

    Just my humble opinion. Other than the first arguments, I agreed with and enjoyed your article.
    May God bless you in all your endeavors.

    • Thanks for your thoughts, Sam. I think Leithart’s point (one I find convincing) is similar to the idea that God can’t do anything that’s inconsistent with his character or being. Can God make a “square circle”? Can he make 2+2=5? Can he make a stone so large he can’t lift it? I think most theologians would limit omnipotence to the logically coherent. (Though I’d love to hear of any you know that argue otherwise).

      So, I think Leithart’s point is that a unitarian God could not be eternally loving, since love presupposes the existence of other persons (not their potential existence, but actual existence). If God is one person and not three, then there was a time in which he did not love—since no beings were in existence for him to love. Therefore, a unitarian God could not be eternally loving.

      Glad you got something from the post regardless. Thanks for chiming in!

    • It doesn’t seem healthy to speculate on if God had chosen to be something other than who He is. God is Trinity, this is the only way to describe our God who is Father, Son, and Holy Spirit. This is how God has revealed Himself to us in the Bible. God is love, love is both given and received between the Father, Son, and Holy Spirit. God is complete in His love because He is Triune. A unitarian god cannot love without a recipient. A unitarian god must create to complete his love.

      • To conclude that God is three is, partly as Tyler replied, a “consequence” of reasoning through things such as the Westminster Confession, superimposed on scripture. Threeness may be deduced, but it is certainly not a necessary inference. Threeness is not explicitly claimed in scripture, so I do not rest there, either. The terms “unitarian God” and “trinitarian God” are somewhat charged and are at least laden with baggage of centuries. It may be healthy to speculate on the nature and constitution of God; it is not healthy to try to nail him down to a human number. None of this precludes anything seen/read as the Incarnate Son or the action of God’s Spirit, e.g., in the Acts of the Apostles.

    • How can God be other than He is? God’s omnipotence and corresponding freedom does not enable Him to be other than He is. It is impossible for God to be other than He has eternally been. It is impossible for God to be other than His very essence. But don’t take it from me: the Holy Spirit says somewhere that “it is impossible for God to lie,” for “God is true” (Heb 6:18; John 3:33). He cannot act contrary to His nature.

      • I thought that part of Christian belief is that all things are possible through God.

        Also, I believe that what this article has left out is the idea that the Holy Spirit is godliness in an essential form that inhabits all and is known to all who embrace it. It is a part of God but is separate from Him, just as Jesus Christ is a part of God but separate from Him. All are glorified by one another, all three glorify the people, and the people glorify the Trinity.

        This article and the comments are a perfect example of a major flaw in Christianity as it refers to human involvement. Lack of coherence and understanding on the part of the Christian community is one of the main problems affecting Christianity. Much of it stems from the desires of humans, which often seem to trump the attempted righteousness of rational beings. However, it is a problem not likely to be solved.

  • Agreed, Michael: His nature is indescribable, although many metaphoric attempts have been made (in scripture and otherwise). God simply is, and He is Who He is, and He will be what He will be.