What is the Trinity?

Short answer

The Trinity is the Christian teaching that there is one God who exists eternally as three persons: the Father, the Son and the Holy Spirit. Each person is fully God, yet there are not three gods but one.

The word “Trinity” does not appear in the Bible. Christians use it as a short name for what Scripture teaches when all its statements about God are held together: there is only one God, and the Father, the Son and the Holy Spirit are each fully God, yet distinct from one another. In the fourth century the church summed this up in the Nicene Creed, which most Protestant, Catholic and Orthodox churches still confess. In short, God is one in being and three in persons.

There is only one God

The Bible never lets go of this conviction. Israel lived among nations that worshiped many gods, and its basic confession, the Shema, which Jews recite morning and evening, begins like this:

Hear, O Israel: The LORD our God is one LORD:
Deut 6:4 · King James Version (1769)

Commentators read this verse in two ways. Matthew Henry thinks that the threefold mention of God’s name and the plural form of the Hebrew word for God hint at a Trinity of persons even in this declaration of God’s unity. Adam Clarke is more cautious: if Moses teaches the Trinity here, he says, it is no more clearly than in the first verse of Genesis. Both agree on the main point: the Lord alone is God.

The prophets repeat it: there is no God besides the Lord (Isaiah 45:5). The New Testament does not change this. Paul insists that an idol is nothing and that there is one God the Father and one Lord Jesus Christ (1 Corinthians 8:4–6), a passage in which John MacArthur sees the full unity of the Father and the Son. James also takes one God for granted (James 2:19). So the Trinity is not belief in three gods. Christians are monotheists.

The Father, the Son and the Spirit are each God

Alongside this, the New Testament speaks of three persons who are each God.

The Father is God. Jesus calls God His Father, and after the resurrection He tells the disciples that His Father is their Father too (John 20:17).

The Son is God. John opens his Gospel with the Word who existed before creation:

In the beginning was the Word, and the Word was with God, and the Word was God.
John 1:1 · King James Version (1769)

Then John says that this Word became flesh in Jesus (John 1:14). When Thomas saw the risen Jesus, he called Him his Lord and his God, and Jesus accepted it (John 20:28). Paul writes that everything God is lives in Christ, who has a real human body (Colossians 2:9): He is fully God and also truly man.

The Holy Spirit is God. When Ananias lied to the Holy Spirit, Peter said he had lied to God (Acts 5:3–4). The Spirit is not an impersonal force. He guides into truth and speaks (John 16:13), and He can be grieved (Ephesians 4:30), which only a person can be.

At the same time, the three are distinct. They are not one person wearing three masks. At the baptism of Jesus all three are present at once:

And Jesus, when he was baptized, went up straightway out of the water: and, lo, the heavens were opened unto him, and he saw the Spirit of God descending like a dove, and lighting upon him: And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased.
Matt 3:16–17 · King James Version (1769)

The Son comes up out of the water, the Spirit descends on Him, and the Father speaks from heaven. Jesus also prays to the Father and promises that the Father will send another Helper, the Spirit (John 14:16–17). The Father is asked, the Son asks, and the Spirit is the gift.

One name, three persons

Before His ascension Jesus sent His disciples to all nations:

Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:

Matt 28:19 · King James Version (1769)

Jesus speaks of one name, not three names, and that one name belongs to the Father, the Son and the Holy Spirit. John Gill draws the conclusion: “there are three persons, but one name, but one God.” Christian baptism has always been done in this name.

The apostles blessed the churches in the same way. Paul ends his second letter to the Corinthians with the only New Testament blessing that names all three persons side by side:

The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Ghost, be with you all. Amen.

2 Cor 13:14 · King James Version (1769)

Peter likewise describes believers as chosen by the Father, set apart by the Spirit and cleansed by the blood of Jesus Christ (1 Peter 1:2).

Scripture does not explain how the three are one. Jamieson, Fausset and Brown note that the doctrine was not fully revealed until Christ came, and that “we know the Holy Three in One more in their relations to us” than in their relations to one another. It is wiser to stay with what God has shown than to press any human picture too far.

Why the Trinity matters

The Trinity is not an abstract puzzle. It shapes the whole of Christian faith.

It shows that love belongs to God’s very being. John says that love is what God is (1 John 4:8): He is not only loving, He is love itself. Jesus speaks of the Father’s love for Him before the world was made (John 17:24). Love did not begin when God created people; it was always there within God.

It explains how we are saved. God our Saviour poured out His kindness, renewed us by the Holy Spirit and gave Him generously through Jesus Christ (Titus 3:4–6). Because we are His children, God has sent the Spirit of His Son into our hearts, and we call God our Father (Galatians 4:6).

And it shapes how Christians pray. Through Christ believers come near to the Father, helped by the same Spirit (Ephesians 2:18). Every prayer offered in Jesus’ name with the help of the Spirit is a small picture of the Trinity at work.

So the Trinity is not about a number that is hard to understand. It is about the God who made us, came to save us in His Son and lives in us by His Spirit.