After briefly defining what is God, we now come to the doctrine of the Trinity. To be honest, for several years the phrasing of Question 2 perplexed me (which reflects the fourth question of the Westminster Shorter Catechism). To ask what instead of who makes God seem impersonal. However, we must remember that God is a title; therefore, Question 2 is answering what we are describing with that title. Question 3 is essentially asking who God is, for even the question itself ascribes personality to God. In the Old Testament, God revealed His name, Yahweh, to Israel, and in the New Testament, He has revealed a deep mystery behind His holy name. We call that mystery the Trinity: there are three persons in the one true and living God.

Although this mystery is profound, it is not complicated like a sort of divine mathematical formula. As we defined God in Question 2, we believe that the Father, the Son, and the Holy Spirit are each fully God. They are the same in substance, equal in power and glory. Furthermore, the Father, the Son, and the Holy Spirit are three distinct persons, so that the Father is not the Son, the Son is not the Holy Spirit, and the Holy Spirit is not the Father. However, the Father, Son, and Holy Spirit are not three Gods, but together are united as the one true and living God. Indeed, as Matthew 28:19 notes, this is God’s name. Yahweh is the Father, the Son, and the Holy Spirit.

How can three be one and one be three? There is the profundity and the grand mystery that must be received by faith. Of course, if God really is infinite, then we should not expect to be able to fully explain every aspect of His divinity. Rather, we ought to bow our heads in humble gratitude that He would reveal such a marvelous truth to us at all.

Of course, since the Trinity is a mystery that will forever elude our full comprehension, many Christians avoid thinking about it at all. They know that it is a necessary belief, but they hope to avoid its complexities by leaving it alone and pursuing more practical matters of the faith. The Trinity, however, is by no means an impractical doctrine; rather, it ought to be a truly wondrous revelation to us. To help us glimpse the wonder of our Triune God, let us glimpse how it practically shapes our everyday faith.

First, our very belief in Jesus as Lord, which is in many ways the foundational confession of the Christian faith, is rooted in the Trinity. Indeed, at His baptism (in inauguration of His ministry), the Father spoke, and the Holy Spirit descended as a dove upon Him. Jesus, the Son, is the image of the invisible God, the exact imprint of His nature. Jesus is fully Yahweh, and at His baptism the Father and the Spirit testified to His radiance of the divine nature.

Second, the mission of Christ’s church, which is now His earthly body, is to make more disciples of Jesus throughout every nation upon the earth. These disciples are declared to belong to Jesus’ church through the sign of being baptized in the name (singular) of the Father, Son, and Holy Spirit. Indeed, we could call baptism an adoption ceremony, where the person baptized is publicly receiving their new family name.

Third, throughout the letter of Ephesians particularly, Paul explicitly teaches the necessity of the Trinity for our very salvation. We were chosen and predestined for adoption by the Father, redeemed and forgiven through Christ, and now sealed and secured by the Holy Spirit. In other words, the Father ordained, Jesus accomplished, and the Spirit applies our salvation. Or as Paul notes, “For through him [Jesus] we both have access in one Spirit to the Father” (Ephesians 2:18).

Finally, even our very prayers can only be Trinitarian. As Jesus taught us, we primarily pray to the Father, yet our access to the Almighty can only come through the person and work of Jesus, who has reconciled us in Himself to God. Through Jesus alone as our high priest and mediator, we have been adopted by the Father and are now able to pray to Him as His children. Furthermore, our prayers are brought through Christ to the throne of God by the power of the Spirit who dwells within us. By Christ, we are made children of God, but “the Spirit himself bears witness with our spirit that we are children of God” (Romans 8:16). Paul calls us to pray “at all times in the Spirit” (Ephesians 6:18) because we are utterly dependent upon the Spirit to enable us to truly pray.

Our belief in Christ, the call to make disciples, our salvation, and our prayers are all rooted in the triune nature of God. The Trinity, brothers and sisters, is not a doctrine to be left to the theologians for scholarly discussion. This is the nature of our great God and Savior. This is who the one true and living God is. And the Trinity is infinitely practical to us as we strive in all things to know and love Him more deeply through His Word.