Pope Leo XIV has issued a new Apostolic Letter, In unitate fidei, inviting Christians worldwide to deepen their shared profession of faith as the Church commemorates the 1,700th anniversary of the First Council of Nicaea. The document was released on Nov. 23, the Solemnity of Christ the King, just days before the Pope departs on an Apostolic Journey to Türkiye, where he will visit İznik—the historic site of Nicaea.
The Pope said he hopes the anniversary will encourage believers “to renew [their] enthusiasm for the profession of faith,” according to Vatican News. He emphasized that the unity expressed in the Nicene Creed remains a cornerstone of Christian identity and a powerful force for hope in an unsettled world.
“In the unity of faith, proclaimed since the beginning of the Church,” Pope Leo wrote, “Christians have been called to walk in harmony, guarding and transmitting the gift they have received with love and joy,” according to Vatican News. He pointed to the Creed’s proclamation of Christ’s divinity—first articulated formally at Nicaea in 325 AD—as “the heart of the Christian faith.”
The Pope also highlighted the timeliness of this anniversary in the midst of the Holy Year dedicated to Christ our hope. Calling the overlap “a providential coincidence,” he observed that the Nicene-Constantinopolitan Creed remains a unifying prayer professed by Christians each Sunday. “This enduring confession of faith has been the common heritage of Christians,” he affirmed, “and it deserves to be professed and understood in ever new and relevant ways,” according to Vatican News.
Amid global instability, Pope Leo insisted that the Creed continues to ground Christians in hope despite present crises. “In these difficult times we are living, amid so many concerns and fears, threats of war and violence, natural disasters, grave injustices and imbalances, and the hunger and misery suffered by millions of our brothers and sisters,” he wrote, “this Creed gives us hope,” according to the same source.
A significant portion of the Letter looks toward the ecumenical significance of Nicaea. The Pope recalled that the Council’s work remains foundational for ongoing dialogue between the Catholic Church, the Orthodox Churches, and Protestant communities. While acknowledging that “full visible unity” has not yet been achieved, he stressed that modern ecumenical efforts have revealed profound common ground. As he noted, “ecumenical dialogue, founded on one baptism and the Nicene-Constantinopolitan Creed, has led us to recognize the members of other Churches and ecclesial communities as our brothers and sisters in Jesus Christ,” according to Vatican News.
Pope Leo reiterated the essential truth at the core of all ecumenical efforts: “Truly, what unites us is much greater than what divides us!”
The Pope said that in a fractured world, a visibly united Christian witness can become “a sign of peace and an instrument of reconciliation,” playing a vital role in fostering global peace, according to the report.
Looking ahead, he encouraged Christians to use the Nicene Creed as a “reference point” for shared prayer, dialogue, and renewed understanding, while also urging believers to “leave behind theological controversies that have lost their raison d’être.” His Letter emphasizes that authentic ecumenism seeks not a return to the early Church nor a mere acceptance of current divisions, but a forward-looking reconciliation rooted in charity and truth.
“The restoration of unity among Christians,” he wrote, “does not make us poorer; on the contrary, it enriches us,” Vatican News reported.
Pope Leo concluded by inviting all Christians to pray together for the guidance of the Holy Spirit, asking that the Spirit “accompany and guide us in this work.”
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