“I believe in one God, the Father Almighty, maker of heaven and earth”—thus begins the Nicene Creed, recited every Sunday by Christian congregations around the globe. Though rarely noted by trinitarian Christians, the creed specifies, not the Holy Trinity, but the Father as the one God. The creed, of course, goes on to state “And in one Lord Jesus Christ” and “And in the Holy Ghost”; but it is the Father who is named the one God. This manner of speech reflects the creed’s biblical and liturgical roots. The apostolic Church did not proclaim a different God than the one God of Israel, just as Jesus himself did not. Our Lord no doubt offered the traditional prayers of synagogue Judaism and recited the Shema. “Why do you call me good?” Jesus asked the rich young man. “No one is good except God alone” (Mark 10:18). Yet the resurrection and ascension of Jesus compelled the Church to advance a new identification of the one God. He was no longer only the divine Creator who had delivered Israel from bondage in Egypt and given her the gift of Torah. He was now, as the Apostle Paul puts it, “the God and Father of our Lord Jesus Christ” (2 Cor 11:31). This new identification was coupled with the confession of Christ as being himself divine. As the Roman governor Pliny the Younger reported to the Emperor Trajan at the beginning of the second century, the Christians gather each week in assembly and “sing a hymn to Christ, as to a god.” Pliny no doubt thought of the Church as but another polytheistic cult; but Christians knew better. There is one God, the Father Almighty, maker of heaven and earth; and the Lord Jesus Christ is his Son. John Behr elaborates:
The Father alone is the one true God. This keeps to the structure of the New Testament language about God, where with only a few exceptions, the word “God” (theos) with an article (and so being used, in Greek, as a proper noun) is only applied to the one whom Jesus calls Father, the God spoken of in the scriptures. This same fact is preserved in all ancient creeds, which begin: “I believe in one God, the Father …”
“For us there is one God, the Father … and one Lord Jesus Christ” (1 Cor 8:6). The proclamation of the divinity of Jesus Christ is made not so much by describing Him as “God” (theos used, in Greek, without an article is as a predicate, and so can be used of creatures; cf. John 10:34-35), but by recognizing Him as “Lord” (Kyrios). Beside being a common title (“sir”), this word had come to be used, in speech, for the unpronounceable, divine, name of God Himself, YHWH. When Paul states that God bestowed upon the crucified and risen Christ the “name above ever name” (Phil 2:9), this is an affirmation that this one is all that YHWH Himself is, without being YHWH. This is again affirmed in the creeds. “And in one Lord Jesus Christ, the Son of God … true God of true God.”
But of course it is one thing to confess that there is one God and Jesus is his eternal Son (and let’s not forget the Spirit); it’s another thing to explain how this confession does not imply some form of polytheism. It was the burden of the 4th century Church to tackle this theological challenge and to forge, if not an explanation, at least a coherent statement and grammar of the trinitarian mystery. St Athanasius, St Basil of Caesarea, St Gregory of Nyssa—each made decisive contributions to the Church’s formulation of the doctrine of the Holy Trinity; but perhaps no one’s writings were more important and formative than those of St Gregory the Theologian. In the words of Christopher Beeley: “Gregory of Nazianzus not only offered the most powerful and comprehensive Trinitarian doctrine of his generation, but, as the later fathers soon recognized, he stands out as the preeminent theologian of the fourth century, second only to Origen among the great fathers who came before him” (Gregory of Nazianzus on the Trinity and the Knowledge of God, p. 319).
The heart of St Gregory’s trinitarian vision is the monarchy of the Father, as revealed in the economy of salvation. God the Father is the uncaused cause of the eternal Trinity and the source of the Son and Holy Spirit (see especially Christopher Beeley, “Divine Causality and the Monarchy of God the Father in Gregory of Nazianzus,” Harvard Theological Review [April 2007], 199-214).