In many places throughout the world, Christians observe Pentecost Sunday as a celebration of God as the Trinity — three divine Persons living eternally in perfect unity: Father, Son, and Holy Spirit. The Trinity is the mystery at the heart of Christianity, and from the beginning it distinguished the apostolic Faith from everything else. It is the foundation of every Christian creed; all other dogmas, all other revelation, come from the fact that God is three in one.
The Apostles preached, insistently, that “God is one.” St. Paul said it plainly (Rom. 3:30; 1 Cor. 8:4–6; Gal. 3:20), as did St. James (James 2:19). In the entire New Testament, there is nothing to suggest a second god — a god besides God.
The Apostles’ monotheism was continuous with their religious herita e. God had said through the prophet Isaiah: “I am the LORD, and there is no other, besides me there is no God” (Isa. 45:5). And, in the time of Jesus, Jews daily recalled the words of Moses: “Hear, O Israel: The LORD our God is one LORD; and you shall love the LORD your God with all your heart, and with all your soul, and with all your might” (Deut. 6:4–5). The God preached by the Apostles is one, and he demanded a total and undivided commitment from anyone who would enter his covenant.
Yet from the first day of the Church’s life, it was clear that the one God is also three. As Peter preached his first public sermon, he spoke of the Father, the Son, and the Spirit: “Being therefore exalted at the right hand of God, and having received from the Father the promise of the Holy Spirit, [Jesus] has poured out this which you see and hear” (Acts 2:33).
The God Peter preached was not a solitary being, but an eternal communion. The God revealed on Pentecost was interpersonal. Only of such a deity could the Apostles say: “God is love” (1 John 4:8, 16).
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The Apostles grounded this most fundamental belief in a revelation given by Jesus himself. In the last sentence recorded in St. Matthew’s Gospel, Jesus instructed his disciples to baptize “in the name of the Father and of the Son and of the Holy Spirit” (Matt. 28:19). They were to act in one divine “name” that clearly applied to three distinct persons. Father, Son, and Spirit share the “name” of God equally. Jesus’ Great Commission, then, was the immediate background for Peter’s first proclamation.
But even before the Great Commission, Jesus had spoken of himself as “one” with the Father (John 10:30). The being of the Father and Son, he said, was relational and inseparable: “the Father is in me, and I am in the Father” (John 10:38). As God had revealed himself to Moses by the name “I AM” (Exod. 3:14), so Jesus claimed that name as his own. “Truly, truly, I say to you, before Abraham was, I AM” (John 8:58). Only immortal, eternal God could make such a statement.
Nevertheless, Jesus was clearly not the same person as the one he addressed as “Father” — and who identified Jesus as “beloved Son” (Mark 1:11; 9:7).
Jesus knew that he was divine, and he applied unmistakably divine titles to himself, such as “lord of the sabbath” (Luke 6:5). His appeal to God as “Father” was perceived as a divine claim, which the Pharisees condemned as blasphemy and supreme arrogance. “This was why the Jews sought all the more to kill him, because he . . . called God his Father, making himself equal with God” (John 5:18). And Jesus did not back away from those charges. Instead, he expressed his expectation “that all may honor the Son, even as they honor the Father” (John 5:23).
From the reactions of his opponents, we can see that Jesus’ self-understanding was scandalous. Nevertheless, the disciples and evangelists reported the Master’s divine titles and claims without commentary, explanation, or defense. They had received a revelation — an idea usually rendered by the Greek apokalypsis, which means “unveiling.” Jesus had shown them something that had previously been veiled from human sight, something humanity could not have discovered on its own. The Apostles were duty-bound to report the content of the revelation, even though they could not pretend to comprehend it.
Jesus had, moreover, spoken of a third divine Person — distinct from the Father and Son yet united to them. Jesus spoke of the Holy Spirit as someone like himself: “another Counselor” (John 14:16) —yet, again, someone whom the Father could “give” and “send” (John 14:26). The Holy Spirit would himself be an active agent — a person and not a force — teaching and reminding the disciples of all that they needed to know.
The divinity of the Spirit was self-evident to the Apostles. In his interrogation of the wayward Ananias and Sapphira, Peter used the terms God and Holy Spirit interchangeably (compare Acts 5:4 and 5:9).
Such was the God proclaimed by the Apostles — and experienced by thousands of people in the New Testament period.
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Christians, over time, would reflect on the mystery and see hints of it in the Old Testament. They noticed that the creation story portrays God using the first person plural, us and our, to speak of himself and not the singular me and my: “Let us make man in our image, after our likeness” (Gen. 1:26, emphasis added). God is one, and his singularity is reflected in the verb forms of the narrative; and yet, when he speaks, he speaks as a collective.
Later in the book of Genesis, God’s promise appears to Abraham by means of three messengers. Other books of the Bible present God’s wisdom as a person (see Proverbs 1:20 and chapters 7–9). Similarly, “the word of the Lord” appears often as not simply a message, but a messenger, who comes and goes (for example, 1 Kings 17:2). When Jews in the diaspora composed the Targums, paraphrased and expanded versions of the books of the Bible, they often depicted “the Word” (Aramaic memra) as a personal figure.
The most prominent Jewish contemporary of the Apostles, Philo of Alexandria, speculated much about God’s “Word.” Philo personifies the Word as the mediator of God’s revelation; God is known in and through the Word. For Philo, the Word is a deuteros theos — a “second god”! — and yet is also the archetype of man.
Other religious Jews were discussing the possibility of a plurality of “powers” in heaven. Yet none went so far as the author of the fourth Gospel, who wrote: “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” (John 1:1, 14). For the early Christians the Word was eternal and transcendent, but became a man in order to save the human race. The apostolic Faith proclaimed the eternal “Word” as enfleshed in the historical Jesus.
The word flesh (Greek sarx) was graphic and must have been scandalous. The same term could be used to describe meat hanging in the marketplace. Here it describes the human body of God. (Later, in John 6:51, Jesus will use the same term, sarx, to describe his body given as “bread . . . for the life of the world.”)
The New Testament doctrine of God was revealed at Pentecost — revealed in the words of St. Peter and in the event itself. But nowhere in Scripture is it presented systematically. The word Trinity appears nowhere in the Bible.
Nevertheless, the testimony of the Apostles is clear. The awaited Messiah, sent by God, was not merely one of the great men of history, but rather God himself. The Holy Spirit, promised by Jesus, in turn, was not an impersonal gift, but the gift of a divine person. From the beginning, the Church instinctively worshiped Jesus and the Holy Spirit as God. St. Paul prayed to the Father and Jesus together:
Now may our God and Father himself, and our Lord Jesus, direct our way to you; and may the Lord make you increase and abound in love to one another and to all men, as we do to you, so that he may establish your hearts unblamable in holiness before our God and Father, at the coming of our Lord Jesus with all his saints. (1 Thess. 3:11–13)
Paul also pronounced blessings in Jesus’ name (Rom. 16:20; 1 Cor. 16:23) and in the name of the Trinity: “The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all” (2 Cor. 13:14).
The most ancient Christian homily we possess outside Scripture begins with the line: “Brethren, it is fitting that you should think of Jesus Christ as of God, as the Judge of the living and the dead.” And one of the earliest pagan reports about Christianity, the letter of Pliny the Younger to the emperor Trajan, describes a congregation gathered to “sing hymns to Christ as to a god.” The New Testament contains several passages that testify to Jesus’ divinity and that seem to be cast in a musical form (John 1:1–18; Phil. 2:5–11; Col. 1:11–15). Hymns to the divine Christ were likely part of Christian worship from the beginning.
What was implicit in Scripture became explicit in the Church’s worship — and made more explicit still in the speculative theology of the following generations. By the end of the second century, Greek and Latin writers had coined new words to describe the mystery of the three in one: Trinas in Greek, Trinitas in Latin — the etymological sources of the English word Trinity.
But the earliest proof is in the Church’s worship of God as Father, and of Jesus, and of the Holy Spirit. A maxim of the early Church tells us: The law of prayer is the law of belief.25 And the Church has prayed consistently in a Trinitarian way since the time of the Apostles.
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The God revealed at Pentecost was not a new God. He was, as the disciples proclaimed to the Jews in Jerusalem, “the God of Abraham and of Isaac and of Jacob, the God of our fathers” (Acts 3:13; 7:32).
The experience of that God was decidedly different. The eternal Word had “pitched his tent” among his people; that’s the literal meaning of the Greek in John 1:14. And, as if that were not close enough, he promised that they would share his life in a still deeper way. He would “abide” in them, and they would abide in him (John 15:4–10). They would be “filled” with the Holy Spirit (Acts 2:4; 4:8; 6:3, 5; 7:55; 13:52).
God would live in the believers, as believers lived in God. God shared human nature, so that humans might come to share his divine nature. St. Paul said: “For you know the grace of our Lord Jesus Christ, that though he was rich, yet for your sake he became poor, so that by his poverty you might become rich” (2 Cor. 8:9; see also Gal. 4:4–6). As Jesus was the Son of God, so the members of his Body, the Church, would know themselves to be children of God (see 1 John 3:1–2).
This was the deepest meaning of salvation. Jesus came “to save his people from their sins” (Matt. 1:21); but the cleansing from sin was a preparation for their new life as God’s children. Around the same time the Fathers were developing a language to describe the Trinity, they were coining terms just as bold to describe salvation. They called it divinization and deification, to emphasize the reality that Christians were God’s children. Jesus’ promise of the Spirit was not a word game. It was the promise of a share in God’s very nature (see 2 Pet. 1:4).
That sudden infusion of divine power explains the ecstatic behavior of the disciples on the day of Pentecost. It also explains the power with which the Apostles worked miracles from that day forward. It is perhaps the only plausible explanation for the success of the work of evangelization in those first generations. The sociologist Rodney Stark estimates that the Christian Church grew, over its first three centuries, at a steady rate of 40 percent per decade.
That’s not something the Apostles — as we know them from the New Testament — could accomplish. Remember: Peter was a coward, Thomas a doubter, James and John ambitious dreamers.
With military might and a wealth of resources, Alexander the Great had failed to conquer the world. So had imperial Rome. Yet believers, or rather Christ, who lived in them (Gal. 2:20) and enabled them to act with his divine power, would succeed.
Editor’s note: This article is an excerpt from Ministers and Martyrs: The Ultimate Catholic Guide to the Apostolic Age, which is available from Sophia Institute Press as an ebook or paperback.
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