Second, this God is the Father of the Lord Jesus Christ. “Blessed be the God and Father of our Lord Jesus Christ, the Father of mercies and God of all comfort” (2 Cor. 1:3). In other words, when Jesus speaks of His Father, He is speaking of the one God. “This was why the Jews were seeking all the more to kill him, because not only was he breaking the Sabbath, but he was even calling God his own Father, making himself equal with God” (John 5:18; see 17:1–5). In short, according to Scripture, the Father is God.
Third, in numerous ways, Scripture reveals that Jesus Christ is God. “In the beginning was the Word, and the Word was with God, and the Word was God. . . . And the Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth” (John 1:1, 14). Both Paul and Peter speak of our “God and Savior Jesus Christ” (Titus 2:13; 2 Peter 1:1). To Him are given titles that belong only to God (for example, Isa. 44:6; 48:12; see Rev. 1:8; 22:12–13). He does works that only God can do (for example, Matt. 9:1–8). According to Scripture, the Son is God.
Fourth, Scripture reveals that the Holy Spirit is God. There is no one and nothing other than God who is eternal, yet the Holy Spirit is revealed to be the “eternal Spirit” through whom Christ offered Himself to God the Father (Heb. 9:14). Peter indicates that to lie to the Holy Spirit is to lie to God (Acts 5:3–4). There is one God. The Father is God. The Son is God. And the Holy Spirit is God.
Fifth, Holy Scripture reveals that the Father, Son, and Holy Spirit are distinct. The Father is not the Son. “All things have been handed over to me by my Father, and no one knows the Son except the Father, and no one knows the Father except the Son and anyone to whom the Son chooses to reveal him” (Matt. 11:27). Jesus prays to the Father (for example, John 11:41–42), an action that would be a farce were the Father and Son merely two modes of the one God. He is our advocate with the Father (1 John 2:1). The Father is not the Son, and the Son is not the Father. The Son is also not the Holy Spirit. The Holy Spirit descends upon the Son (Luke 3:22). Jesus sent the Holy Spirit (John 15:26; 16:7), who is another Comforter (John 14:16 KJV). The Son and Holy Spirit (and the Father) are distinguished in the Great Commission (Matt. 28:19). The Father is not the Holy Spirit. The Father sends the Spirit (John 14:16; 15:26). The Spirit intercedes for us (Rom. 8:26–27).
When the fullness of God’s self-revelation in Scripture is not taken into account, heresy is the result. Those who emphasize the oneness of God to the neglect of what Scripture teaches regarding the deity of the three persons fall into errors such as Adoptionism, Modalism, and Arianism. Those who fail to grasp what it means to say that the Father is God, the Son is God, and the Holy Spirit is God, fall into various forms of subordinationism. Those who emphasize the three to the neglect of what Scripture teaches about the oneness of God fall into forms of tritheism.
Gregory’s quote reveals how carefully we have to think about our triune God. He describes a kind of perpetual conscious oscillation between thinking of God as one and thinking of God as three. He deems this necessary because our minds cannot fully grasp both truths simultaneously and we have a tendency to stop at one or the other, thus becoming either practical Unitarians or practical tritheists. John Calvin delighted in this quote because, like Gregory, he understood that there is an element of mystery involved in the doctrine of the Trinity. He also understood that this mystery should not elicit a feeling of skepticism about what God has revealed. Instead, it should elicit wonder and worship. Gregory’s words beautifully express this sense of awe and adoration. With Calvin, we too can learn from and delight in them.