Why does the Council of Nicaea matter today? Because nearly 1,700 years after it convened in the summer of A.D. 325, its legacy still unites Christians across the globe in professing the same foundational belief: that Jesus Christ is true God from true God, eternally begotten of the Father. In a world fractured by theological and ecclesial divisions, the Council of Nicaea reminds us that the unity of the Church must be unity in faith.
As Pope Leo XIV recently emphasized, “That council represents a fundamental stage in the development of the creed shared by all the Churches and ecclesial communities.” He added, “While we are on the path towards the reestablishment of full communion among all Christians, we recognize that this unity can only be unity in faith” (Catholic News Agency, 2025).
The first ecumenical council, convened by Emperor Constantine in Nicaea—modern-day northern Turkey—was an unprecedented gathering of more than 300 bishops. Constantine, a convert to Christianity and recent unifier of the Roman Empire, saw a need to resolve theological disputes threatening the peace and doctrinal clarity of the Church, particularly the Arian heresy. This heresy, advanced by the priest Arius, claimed that Jesus Christ was not eternal, but rather a created being.
“Arius began to preach something that was scandalous to many Christian believers,” Dominican Father Dominic Legge explained, because he argued that “the Son was not always [in existence]” and “came into existence by the Father’s will” (CNA). Arius believed that Jesus was “made God by participation” and not divine by nature. This view, Legge warned, “threatened the central truth of Christianity that God became man for our salvation.”
The bishops overwhelmingly rejected Arius’ theology. In nearly unanimous agreement—with only two dissenting votes—they declared that the Son is “God from God, true God from true God, begotten not made, of one substance with the Father.” This phrase remains a cornerstone of Catholic theology, affirming Christ’s eternal divinity and consubstantiality with the Father. It became the backbone of the Nicene Creed, still recited at every Catholic Mass, Orthodox Divine Liturgy, and many Protestant services.
One of the fiercest defenders of Christ’s divinity at the council was St. Athanasius, who later wrote that “the Scriptures declare the Son’s eternity,” citing John 1:1 and John 8:58. “‘I am the Truth,’ not ‘I became the Truth,’ but always, ‘I am — I am the Shepherd — I am the Light,’” Athanasius wrote in First Discourse Against the Arians, underscoring that Christ’s own words affirm His eternal, divine nature.
Although the council successfully defined Christ’s divinity, its acceptance was not immediate or universal. According to Thomas Clemmons of The Catholic University of America, “It’s later tradition that will affirm it.” The decades following Nicaea saw fluctuating imperial support between Nicene defenders and Arian sympathizers. It wasn’t until A.D. 380, under Emperor Theodosius, that Nicene Christianity was officially declared the state religion of the Roman Empire. A year later, the First Council of Constantinople expanded the Nicene Creed to affirm the divinity of the Holy Spirit and the Church.
Despite popular myths, the Council of Nicaea did not create the biblical canon, invent the papacy, or suddenly establish the Church. As Clemmons explained, these are “prominent misconceptions” not grounded in historical fact. The council instead “confirmed the faith of the early Church” and addressed jurisdictional disputes among bishops already in place.
The Council of Nicaea marks a definitive moment in Church history—a moment when, in the face of grave heresy and division, the bishops of the Church spoke with one voice. Their decision preserved the truth of the Incarnation and provided the Church with a creed that has weathered centuries of conflict, reform, and renewal.
Seventeen centuries later, Christians still proclaim, “I believe in one Lord Jesus Christ, the Only Begotten Son of God… true God from true God.” In doing so, they echo the faith of the Council of Nicaea—faith in the eternal Son who came to save us.
