The Trinity is the doctrine that God eternally exists as one God in three distinct Persons: the Father, the Son, and the Holy Spirit. These three Persons are co-equal, co-eternal, and fully share the one divine being, or essence. This is not a belief in three gods (tritheism) nor in one person revealing himself in three different modes (modalism). It is one God (Deut 6:4) who subsists in a tri-personal way (Matt 28:19; 2 Cor 13:14).

We can understand this partly by distinguishing between “being” (what something is) and “personhood” (who someone is). A tree, for example, possesses being but has no personhood. A human possesses both one being and one personhood. God is unique: He possesses one single, indivisible divine being and three distinct Persons. The Father, Son, and Spirit are not three parts of God; each Person is fully God.

While God is eternally one being and three persons, we can appreciate these distinct realities through different perspectives. God’s oneness and unity are most clearly seen in His eternal existence and attributes: His self-sufficiency, His immutability, and His singular divine will.

Conversely, God’s tri-personhood is most clearly understood in His interactions with the world. We see this in the work of salvation: God the Father, who plans redemption and sends the Son (Eph 1:3-6); the incarnate Son, who willingly accomplishes redemption on the cross (John 1:14; 3:16); and the indwelling Spirit, who applies redemption and sanctifies the believer (John 14:16-17).

Both the single being and the triune personhood exist eternally within the Godhead and are equally active in creation (Gen 1:1-2) and redemption. The Trinity is revelaed in both the Old and New Testament, showing that He is eternally relational within His own being.