Introducing the Trinity: The Mystery at the Heart of Christianity

The charge has long been levelled against the doctrine of the Trinity that it is difficult to describe, impossible to understand, and not found in the Bible, anyway. And yet for centuries, orthodox Christianity has affirmed it as a core tenet of the faith.

Every major Christian tradition affirms the trinitarian formulation of the Christian God. Protestants, Anglicans, Orthodox, and Catholics disagree about a great many things, but they are united on the truth about the Trinity, affirming with one voice that the God Christians worship exists in three persons: Father, Son, and Holy Spirit.

But why is this doctrine so important? Why is it crucial to orthodox Christianity that we affirm the Trinity? I am sure that we could list many reasons, but three come immediately to mind.

The first is that the Trinity is indispensable for understanding the character of the Christian God. Christianity occupies a unique position among the world’s religions. Like Judaism and Islam, it is monotheistic, affirming that there is one God, who alone is worthy of worship and allegiance. And yet, unlike any other religious tradition, Christianity confesses that this one God exists in three distinct persons: Father, Son, and Holy Spirit.

You will not find that anywhere else. But it is important to recognise, because if you want to truly know the God of the Bible—the God of Abraham, Isaac, and Jacob—you must embrace what Scripture reveals about him through the lens of the Trinity. There is simply no other way to see him clearly.

A second reason is that the Trinity gives us a framework for understanding Christian love and unity. Scripture calls believers to love one another and to guard the unity of the Spirit in the bond of peace. That is a high and demanding call, especially given our natural tendency as sinful human beings to divide rather than to unify. But the doctrine of the Trinity shows us that this kind of unity is not a human invention but a reflection of something eternal.

Father, Son, and Holy Spirit are perfectly unified in purpose and bound together in a love that knows no division, even as each person is distinct in function. The triune God now calls his church to model that same relational love. Understanding the Trinity, even imperfectly, gives us both the pattern and the motivation to pursue unity.

The third reason is that the Trinity is the only framework within which the claims of Jesus Christ make sense. Jesus is not merely a great moral teacher or a prophet in a long line of prophets. According to Scripture, he is the eternal God who entered human history, taking on flesh, living a sinless life, dying a sacrificial death, and rising victoriously from the grave before ascending to the right hand of the Father. To affirm who Jesus truly is, we must affirm the Trinity. We must be able to say, with the church across the ages, that he is both the Son of God and God the Son.

These are the convictions that have for centuries driven an embrace of Christian trinitarianism.

There is no shortage of critics who have argued that the Trinity is an invention of later Christians to explain the development of Christian doctrine. I recently came across an interview with Bart Ehrman, who denies that Christian teaching about the Trinity can be found in the Bible. While he displays an accurate enough understanding of what the doctrine is, and while he recognises that the Bible does speak of Father, Son, and Holy Spirit, he denies that the teaching, as held in Christian theology, arises from the text.

Erhman argues that the Trinity developed as a theological solution to a tension that Christians found in the text of Scripture. Since the Bible seems to portray Jesus and the Holy Spirit as divine, and yet clearly affirms there is only one God, a solution was necessary to harmonise these teachings.

He claims that the doctrine of the Trinity as we understand it was not universally embraced, even after its development. Subordinationism (that Jesus is divine but created by and inferior to God) and modalism (that the persons are actually one being manifested in three different modes) were common competing ways to understand the claim of Scripture, while others simply denied the deity of Christ entirely. The Council of Nicaea was convened to answer this question and decided on the trinitarian formulation with which we are familiar. Even after that, he claims, it was a long time before the doctrine as we know it was widely accepted.

If the doctrine of the Trinity as traditionally affirmed by Christianity is “orthodox,” it is not necessarily because it is true, says Erhman, but because it is the most popular. The Trinity became the dominant way to explain the nature of God not because it is what the Bible actually teaches, but because of historical development and theological power dynamics. In his view, the Trinity is a constructed doctrine that did not arise from the text but developed over centuries of theological debate.

Erhman’s view is popular among sceptics, but does it accurately explain the origins of the Trinity, or do the claims of historic Christianity actually arise from the text of Scripture?

The pastor of a church with which my own church is in association recently began a brief, four-part sermon series on the doctrine of the Trinity. While I rarely listen to preaching outside of my own church, a sermon series on the Trinity was intriguing enough for me to listen to the recordings of his sermons. I have found them helpful, edifying, and illuminating.

For the next several posts, I want to explore the doctrine of the Trinity. This is a huge topic, and I cannot hope to cover it in any great detail, but I believe it will prove helpful to my own thinking to crystallise some of the things the Bible teaches about the Trinity. While it is a doctrine that we can never fully grasp with our finite mind, it is also not merely a puzzle for the intellectually curious. It is how God has revealed himself to be and is therefore formative for our worship.

That point warrants reflection. The first commandment tells us we may worship only the one true God. The second, in forbidding idols, instructs us that we must worship him on his own terms—in the way he has revealed himself to be known. If we are going to worship God according to knowledge, if we are going to approach him as he is rather than as we might prefer him to be, we must worship him as the triune God, who exists as Father, Son, and Holy Spirit. May our reflection on his nature drive us to worship him more deeply.