Two Minute Theology is a series that introduces theological concepts in around 600 words.

If you only had two minutes to introduce someone to the Christian doctrine of the Trinity, what would you say?

The best place to begin is with the gospel, because that is where God is finally revealed to us as Father, Son, and Holy Spirit. While the Old Testament hints at the Trinity, we can only recognize the doctrine when reading the OT in light of the New Testament. In the NT, God saves us by sending the Son and the Spirit. Ephesians 1 praises the Father for planning our redemption, the Son for accomplishing our redemption, and the Spirit for applying our redemption. We call this the economic Trinity, God’s “economy” or “household management” (oikonomikos, Eph. 1:10) of redemption.

Of course, the Trinity has always existed in perfect blessedness. If God had never created or redeemed us, he would still exist as Father, Son, and Holy Spirit. When speaking about God-in-himself, we use the term immanent Trinity. This is what we usually think of when we hear the word “Trinity.” The trouble is that if we start here, the Trinity seems like a confusing enigma in the sky, an abstract idea that we need to confess but don’t see as relevant for our Christian life or gospel proclamation. Instead of using simplistic illustrations, we should help people to see that the Trinity is like the Father sending the Son and the Spirit. God has revealed his eternal triune being through his triune work of redemption. No Trinity, no gospel.

The good news of the gospel is that it brings us home to the God who is Trinity. The Christian life is lived in spiritual union and close fellowship with the Father, Son, and Spirit. This is why all Christians are baptized “in the name of the Father and of the Son and of the Holy Spirit.” Matthew 28:19 is the most important text on the Trinity and the foundation of all Christian teaching. There is something one in God: “the name,” singular. But there is also something three in God: it is the name “of the Father and of the Son and of the Holy Spirit.”

For centuries, the church has used the word nature (sometimes substance or essence) to label what is one in God and the word persons to label what is three in God. God is one in his nature and three in his persons. Each person has the full divine nature: whatever is true of God is true of the Father, Son, and Holy Spirit. When we say, “Jesus is God,” we are referring to what Jesus is. When we say, “Jesus is the Son of God,” we are referring to who Jesus is: he is always and forever the Son, the same substance as the Father.

There is nothing in creation that is three and one in exactly the same way as God is three and one. One egg has a shell, yolk, and white, but these are three parts of the egg. There are not three parts in God (the heresy of partialism), because God is one, simple (without parts) in his being. One H2O molecule can exist as solid, gas, or liquid, but these are three states or modes of water. The Father, Son, and Spirit are not three modes of being (the heresy of modalism), they are distinct persons.

The Son is distinct from the Father because he is eternally begotten by the Father. This does not mean that the Son is created: because he has the divine nature, he is eternal and uncreated. But in some mysterious way, the Son is from the Father (Jn. 5:26). Likewise, the Spirit eternally proceeds from the Father and the Son (Jn. 15:26). Because the Son is eternally generated by the Father, it is fitting that he should be sent by the Father to accomplish redemption. Because the Spirit eternally proceeds from the Father and the Son, it is fitting that he should be sent by the Father and the Son to apply redemption. The gospel economy reflects something in the eternal relations between Father, Son, and Spirit. The Trinity is like the gospel.