Pope Leo XIV commemorated the 1,700th anniversary of the Council of Nicaea in Turkey. The Pope reflected on the historical context of Arianism, a heresy addressed by the Council. Pope Leo XIV highlighted the importance of orthodox faith in contrast to the claims of Arius. The Pope discussed how the Church should address contemporary challenges, drawing parallels to the historical context of Arianism.
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Pope Leo XIV traveled to Turkey to mark the 1,700th anniversary of the Council of Nicaea on November 28, 2025. He joined Orthodox Ecumenical Patriarch Bartholomew and other Christian leaders for an ecumenical prayer service near the ruins of an ancient basilica in Iznik. This event highlighted unity among Christians while reflecting on the council's historical significance.1
Arianism, named after priest Arius of Alexandria, denied that Jesus Christ was fully divine and equal to God the Father. The Council of Nicaea in 325 AD condemned this heresy and formulated the Nicene Creed, affirming Jesus as "God from God, Light from Light, True God from True God." The creed introduced the term "consubstantial" to describe the shared divine nature of Father and Son.1
Nicaea employed non-scriptural Greek terms like "substance" (ousia) and "consubstantial" (homoousios) to clarify biblical faith against Arian errors. Pope Leo XIV, in his apostolic letter In Unitate Fidei released before the trip, argued these terms served to defend orthodoxy, not replace Scripture. He rejected accusations of "Hellenization" against the Church Fathers, attributing such influences instead to Arius' heterodox views.1
Pope Benedict XVI, in his Regensburg Address, celebrated the integration of Greek philosophy into Christian revelation as providential, linking it to the Gospel's use of "logos." Leo XIV's approach concedes the necessity of Greek language to counter Arian corruption but refutes broader Hellenization claims. This subtle shift in emphasis may shape future developments in Leo's pontificate.1
In a speech at Istanbul's Holy Spirit Cathedral, Pope Leo XIV identified a contemporary "new Arianism" where Jesus is admired only as a human teacher or prophet, diminishing his divinity and lordship. He urged recognition of Christ as the living Son of God guiding history. This echoed Pope St. John Paul II's 1987 address to Chilean youth, challenging them to see Jesus as more than a reformer—indeed, as God's face.1
The Nicaea anniversary underscores the creed's role as a foundation for ecumenical unity. Pope Leo's reflections reaffirm the Church's task of interpreting Christ's identity amid modern challenges, from cultural secularism to doctrinal disputes. By drawing on predecessors like Benedict and John Paul, Leo positions Nicaea's truths as timeless responses to ongoing questions of faith.1
Assess the enduring relevance of the Council of Nicaea for Catholic orthodoxy
The Council of Nicaea, convened in 325 AD, remains a cornerstone of Catholic orthodoxy, having defined essential truths about the divinity of Christ and the unity of the Church that continue to shape doctrine, liturgy, and ecumenical dialogue today. Its Nicene Creed serves as the normative confession of faith for Catholics and many other Christians, safeguarding against heresies while affirming the Trinitarian mystery at the heart of salvation. In an era of theological challenges and calls for unity, Nicaea's legacy underscores the Church's commitment to apostolic tradition, biblical fidelity, and the pursuit of visible communion among believers.
The First Council of Nicaea was summoned amid profound crisis in the early Church, shortly after the Edict of Milan in 313 granted Christians legal recognition under Emperor Constantine. Persecutions had scarred the faithful, but internal divisions threatened unity even more gravely. The Arian controversy, led by the priest Arius of Alexandria, posited that Jesus Christ was not eternally divine but a created being, an intermediary between God and humanity. This view risked undermining the core of Christian salvation: if Christ were not fully God, his redemptive work could not bridge the divine-human divide. Constantine, recognizing the peril to both Church and Empire, convened an unprecedented assembly of over 300 bishops—mostly from the East, with Western representation including legates from Pope Sylvester—to restore harmony. Presided over by the emperor but guided by figures like Bishop Hosius of Cordoba, the council addressed not only doctrine but also practical issues like the Easter date and the Meletian schism.
The council's acts, though fragmentary today, produced the original Nicene Creed, twenty canons on Church discipline, and a synodal letter. These outputs were not mere administrative fixes but defenses of orthodoxy rooted in Scripture and tradition. For instance, Canon 1 regulated the status of clerics affected by persecution, reflecting Nicaea's pastoral concern for a Church emerging from trial. Later councils, such as Carthage in 419, explicitly incorporated Nicaea's statutes into their proceedings, affirming their enduring authority as a benchmark for ecclesiastical governance. This historical intervention established ecumenical councils as instruments of truth, a model that persists in Catholic synodality.
At Nicaea's heart lies the Creed, a baptismal profession that evolved into the Nicene-Constantinopolitan form recited in Masses worldwide. It boldly proclaims: "We believe in one Lord, Jesus Christ, the only Son of God, eternally begotten of the Father, God from God, Light from Light, true God from true God, begotten, not made, of one Being with the Father." This formulation directly countered Arianism by introducing terms like homoousios (consubstantial), affirming Christ's full divinity without compromising monotheism. The Fathers drew from biblical language—echoing John's Gospel and Paul's epistles—while employing philosophical precision to clarify, not innovate, the faith handed down from the apostles.
In Catholic orthodoxy, the Creed is no relic but a living norm. It structures catechesis, liturgy, and theology, ensuring that every profession of faith aligns with Nicaea's safeguards. The International Theological Commission highlights its role as the "confession of faith of the 318 Fathers," especially revered in Eastern Churches as the "Council par excellence," where faith decisions invoke apostolic tradition over mere majority vote. Unlike disciplinary canons, which allow debate, doctrinal affirmations like those on Christ's substance are irrevocable, binding the Church across centuries. The Creed's amplification at Constantinople in 381 addressed further heresies, yet retained Nicaea's core, making it the common heritage of Catholics, Orthodox, and many Protestants. This unity in creed underscores orthodoxy's resistance to relativism, reminding believers that truth is not subjective but divinely revealed.
Nicaea's relevance extends beyond Catholicism to the broader Christian oecumene, fostering dialogue where divisions once prevailed. Pope Leo XIV, in his 2025 address on the 1700th anniversary, described it as a "compass" guiding Catholics and Orthodox toward visible unity, building on Vatican II's momentum. The council's emphasis on shared faith—professed in baptism and liturgy—transcends historical schisms, inviting joint commemoration as a step toward reconciliation. Similarly, the Synod of Bishops in 2024 urged using the anniversary to deepen confession of Christ and explore synodality across traditions, even proposing a common Easter date to amplify missionary witness.
This ecumenical thrust echoes earlier papal reflections. John Paul II, marking the Second Council's centenary, linked Nicaea's tradition to the undivided Church's path, calling Catholics and Orthodox to re-examine differences in light of Christ's prayer for unity (Jn 17:11, 20-21). Nicaea thus models orthodoxy not as isolation but as communion: a faith professed together, guarding against errors while embracing the "seeds of truth" in diverse expressions. In today's fragmented world, it challenges the Church to witness Trinitarian love amid secularism and interfaith tensions.
In the 21st century, Nicaea confronts modern distortions of Christology, from reductionist views in popular culture to theological drifts questioning divine sonship. Pope Leo XIV's Apostolic Letter In Unitate Fidei (2025) ties the anniversary to the Jubilee Year of Hope, urging renewal in professing the Creed amid wars, injustices, and despair. It reaffirms that Christ's consubstantiality with the Father offers abundant life (Jn 10:10), countering Arian-like diminutions that portray Jesus as merely inspirational rather than Savior. The document praises the International Theological Commission's work for illuminating Nicaea's cultural and social implications, showing how orthodoxy informs ethics, science, and society—echoing saints like Albert the Great, who harmonized faith and reason without conflict.
For Catholic orthodoxy, Nicaea demands ongoing vigilance: it invites believers to "come and see" Christ (Jn 1:38-39), integrating creed into daily witness. As John Paul II noted in youth gatherings, this means embodying ideals through action, trusting witnesses over abstract theory. In synodal processes, Nicaea inspires participatory discernment rooted in ancient truth, ensuring the Church's mission remains faithful yet adaptive.
In conclusion, the Council of Nicaea's enduring relevance lies in its unyielding defense of Christ's divinity, providing a creed that unites, a tradition that guides, and a vision of unity that heals. As we approach the 1700th anniversary in 2025, it calls the Church to profess this faith boldly, fostering hope in a divided world through the one Lord Jesus Christ.