A Basic Definition of the Trinity

Thomas Overmiller

Any description of the Trinity must include two basic elements. First, it must affirm that there is one eternal God. Second, it must affirm that this God has always existed as three persons. That is why theologians use trinity to describe this “three-in-oneness” of God. He is one God (uni- means “one”) and three persons (tri- means “three”). Hence, he is triune. One example of a basic statement of the Trinity describes God as “three distinct persons in one divine essence.”¹ A similar statement affirms that “God exists as three persons, yet he is one God.”² Ultimately, it is appropriate to define the Trinity as one eternal God who exists in three coeternal, coequal persons: Father, Son, and Holy Spirit.

Statements like this, which insist that there is one God but three persons, seem incompatible and contradictory. In fact, they seem so incompatible that no person would have devised such a concept.³ In this way, the triune nature of God underscores the divine origin and authority of Scripture as God’s self-revelation, demonstrating that the Bible is no result of human imagination (2 Pet 1:20-21).⁴ So then, the tri-unity of God upholds the divine nature of Scripture, and the Scripture upholds the tri-unity of God as an orthodox doctrine. Furthermore, the triunity of God sets apart the Christian faith as unique from any other religion. No other faith worships such a triune God.

Avoiding Common Misconceptions

To understand the triunity of God in a responsible way requires an awareness of common misconceptions. Modalism (or Unitarianism), for instance, emphasizes the oneness of God, but not as three eternal persons. It alleges that God is one divine being who has manifested himself in three alternate ways – either as Father, Son, or Holy Spirit, but only one at a time. Tritheism, on the other hand, alleges that the Father, Son, and Spirit are three independent gods, which is polytheism. This view emphasizes the three eternal persons, but not as one unified God. Altogether, any description of the Trinity must avoid both errors by firmly accepting the oneness of God and the three persons of God in perfect and eternal harmony.

Embracing the Mystery of the Trinity

Christians believe that God is triune, both one God and three persons, not because the concept makes sense, but because God reveals himself this way in Scripture. Therefore, it is necessary to accept this doctrine by faith. As such, a believer must avoid any attempt to resolve apparent contradictions, knowing that the Trinity defies full comprehension. This does not mean that the doctrine is erroneous, nor does it mean that God has revealed himself in a faulty or incomplete way. Instead, believers seek to understand God through their limited human abilities, which prevent them from understanding the sovereign, incomparable God completely.⁵ Nevertheless, he expects every believer to understand him as fully as possible, to the extent that he has revealed himself in Scripture. This requires prayerful, humble reliance upon the Holy Spirit and careful study of his inspired revelation.

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Thomas Overmiller serves as pastor for Faith Baptist Church in Corona, NY and blogs at Shepherd Thoughts. This article first appeared at Shepherd Thoughts, used here with permission.

This article appeared here. It is an excerpt from a larger piece appearing here.

1. Nathan D. Holsteen and Michael J. Svigel, Exploring Christian Doctrine, vol. 1 (Minneapolis: Bethany House, 2014), 131. [↩]
2. Wayne A. Grudem, Systematic Theology: An Introduction to Biblical Doctrine (Grand Rapids: Zondervan, 2004), 226. [↩]
3. C. S. Lewis, Beyond Personality (New York: Macmillan, 1945), 13. [↩]
4. “It appears that Tertullian was right in affirming that the doctrine of the Trinity must be divinely revealed, not humanly constructed. It is so absurd from a human standpoint that no one would have invented it. We do not hold the doctrine of the Trinity because it is self-evident or logically cogent. We hold it because God has revealed that this is what he is like. As someone has said of this doctrine: Try to explain it, and you’ll lose your mind; but try to deny it, and you’ll lose your soul” (Millard J. Erickson, Introducing Christian Doctrine [Grand Rapids, MI: Baker, 1992], 105). [↩]
5. “We cannot fully understand the mystery of the Trinity. When someday we see God, we shall see him as he is, and understand him better than we do now. Yet even then we will not totally comprehend him” (Erickson, Introducing Christian Doctrine, 104). [↩]