The Trinity: The God Who Is Three-in-One

The Trinity: The God Who Is Three-in-One

The doctrine of the Trinity stands as one of the central mysteries of the Christian faith. It is not a philosophical abstraction but the reality of God as revealed in Scripture: Father, Son, and Holy Spirit — three distinct persons, yet one God. The term Trinity (trias in Greek, trinitas in Latin) does not appear in the Bible, but the reality saturates both Old and New Testaments. Understanding the Trinity guards us from distortions such as modalism (the view that God is one person appearing in three modes) and gives the church a way to confess the God who is eternally relational, self-giving, and love.

The Trinity is the Christian belief that there is one God who exists eternally as three distinct persons: Father, Son, and Holy Spirit. Each person is fully God, sharing the same divine essence, yet they are not the same as one another. The Father is not the Son, the Son is not the Spirit, and the Spirit is not the Father — but together they are one God. This is not three gods, nor one God who simply changes forms, but the mystery of the God revealed in Scripture: unity of being, diversity of persons, perfect in love and action.

The Trinity in the Old Testament

Though the Old Testament emphasizes the oneness of God (“Hear, O Israel: The LORD our God, the LORD is one” – Deut. 6:4), there are hints of plurality within that unity:

• Genesis 1:26 – “Let us make man in our image, in our likeness.” The plural pronouns suggest a divine plurality working together in creation.

• Genesis 18 – Abraham encounters three men at Mamre, a theophany often read by Christians as a foreshadowing of Trinitarian revelation.

• Psalm 110:1 – “The LORD says to my Lord: ‘Sit at my right hand until I make your enemies a footstool for your feet.’” Jesus later cites this to show that David acknowledged the Messiah as distinct from Yahweh yet sharing divine authority.

• Isaiah 48:16 – “And now the Lord GOD has sent me, and His Spirit.” Here, three figures appear: the Lord, the one sent, and His Spirit.

• Zechariah 12:10 – “Then I will pour out a spirit of grace and prayer on the family of David and on the people of Jerusalem. They will look on me, the one they have pierced, and they will mourn for him as for an only son.” Here the Lord (YHWH) is speaking, yet distinguishes between “me” who is pierced, the “Spirit” poured out, and the mourned-for “Son.” This remarkable passage anticipates the crucifixion, the outpouring of the Spirit, and the Father’s role — a clear foreshadowing of Trinitarian revelation.

The Old Testament is not explicit but sets the stage. As Augustine put it, “The New is in the Old concealed; the Old is in the New revealed.”

The Trinity in the New Testament

The New Testament brings Trinitarian revelation into full light:

• The Baptism of Jesus (Matt. 3:16–17) – The Son is baptized, the Spirit descends, and the Father’s voice speaks from heaven.

• The Great Commission (Matt. 28:19) – Disciples are baptized “in the name of the Father and of the Son and of the Holy Spirit” — one name, three persons.

• Paul’s Benediction (2 Cor. 13:14) – “The grace of the Lord Jesus Christ, the love of God, and the fellowship of the Holy Spirit be with you all.”

• John 1:1, 14 – The Word is with God and is God, yet distinct, and becomes flesh in Jesus.

• Acts 5:3–4 – Lying to the Holy Spirit is equated with lying to God.

These passages, among many others, led the early church to confess one God in three persons.

Refuting Modalism

Modalism (also called Sabellianism) taught that God is one person who merely appears in three forms: sometimes as Father, sometimes as Son, sometimes as Spirit. This view fails to account for the simultaneous presence of all three persons in passages like Jesus’ baptism. It also empties God of eternal relational love, since in modalism, God would have no one to love before creation. The Trinity, by contrast, shows God has always existed in love and communion.

Though most pastors affirm the Trinity, many unintentionally slip into modalistic explanations when trying to make the doctrine easier to grasp. The most common example is the “water analogy” — saying God is like water, which can exist as ice, liquid, or vapor. The problem is that water cannot be all three at once; it changes from one form to another. That’s modalism, not Trinitarianism, because the Father, Son, and Spirit do not merely shift forms — they exist as three distinct persons simultaneously. Another popular analogy is the “roles of a man” — one man may be a father, a son, and a husband, yet still one person. Again, this fails, because it portrays God as a single person wearing different hats, rather than three distinct persons who interact in love. Both illustrations collapse into the heresy of modalism because they deny the eternal distinctiveness of Father, Son, and Spirit.

The reason these analogies don’t work is that they flatten the mystery of God into human categories. The Trinity cannot be reduced to a created comparison without distortion. The best way to guard against modalism is to let Scripture define the boundaries: God is one in essence but three in person. The classic confession — Father is God, Son is God, Spirit is God, but the Father is not the Son, and the Son is not the Spirit — avoids the pitfalls of oversimplification. The moment we trade this confession for human analogies, we stop proclaiming the Trinity and start describing a God who doesn’t exist.

The Best Way to Understand the Trinity

No analogy fully captures the mystery, and many common ones (water as ice/liquid/steam, or one man as father/son/husband) actually slip into heresy if pressed too far. The best approach is to confess the reality Scripture presents: one essence (ousia), three persons (hypostaseis). The Cappadocian Fathers summarized it: “They are divided without division, united without confusion.”

The classic diagram of the Trinity — one God in three persons, with each person fully God yet not the other — remains the clearest visual tool to prevent misunderstanding.

Application

Belief in the Trinity is not a dry doctrine but the heart of Christian life:

• Worship: We worship the Father, through the Son, in the Spirit.

• Love: The eternal love within the Trinity is the model for Christian community (John 17:21).

• Salvation: The Father sends, the Son redeems, the Spirit applies. All three persons act in harmony to save us.

Conclusion

The Trinity is not a human invention but the inevitable conclusion of the biblical witness. From Genesis to Revelation, God reveals Himself as one and three: eternally Father, Son, and Spirit. While our finite minds cannot fully grasp this reality, we can confess with the church through the ages: Glory be to the Father, and to the Son, and to the Holy Spirit — one God, now and forever.