THE Pope Leo XIV published on November 23, 2025 a long apostolic letter entitled In unitate fidei ("In the unity of faith") on the occasion of the 1700th anniversary of the first ecumenical council held in Nicaea in 325 AD. This document marks the beginning of an ambitious project to revive unity among the Christian Churches, at a time when ecumenism seems weakened.
Leo XIV It forcefully reminds us that the Nicene Creed, the fruit of a tumultuous council, was born in a context of profound crises and theological controversies. This confession of faith, long considered the common foundation of Christians, affirms in particular the consubstantial divinity of the Son, against the heresy of Arius. For the pope, This text remains "the heart of the Christian faith," a shared heritage upon which authentic reconciliation can be built. It therefore invites us to return to this common foundation in order to move forward on a renewed ecumenical path.
This letter is also an invitation to "walk in harmony," to bear witness to this shared faith with "love and joy" in the midst of a world marked by conflict, injustice, and poverty. It emphasizes that despite institutional divisions, all the baptized are members of Christ and that "what unites us is far greater than what divides us.".
The journey to Türkiye: a symbolic gesture at the heart of Christian history
The project of Leo XIV is fully embodied in his apostolic journey planned from November 27 to December 2, 2025 in Türkiye, specifically in the cities of Ankara, Istanbul and especially İznik, the ancient Nicaea. This pilgrimage is highly symbolic: it is part of the commemoration of the 1,700th anniversary of the founding council and reaffirms the deep link between history, faith and unity.
The program includes an ecumenical prayer meeting at the archaeological site of the ancient Basilica of Saint Neophytos in İznik, with Ecumenical Patriarch Bartholomew I and representatives of the Eastern Patriarchates in attendance. This initiative aims to highlight the historical and spiritual significance of Nicaea, to underscore the need for strengthened dialogue between the Churches, and to support Christian minorities in a region marked by political and social upheaval. Pope Leo XIV wants to make this gathering a concrete act of peace in a society fractured by numerous conflicts.
Furthermore, this journey also carries a strong pastoral dimension, with a message for refugees and vulnerable populations, particularly in Lebanon, where the pope will then go. According to him, the faith professed in the Nicene Creed must also nourish the social and moral commitment of Christians in the contemporary world.
A renewed commitment to a common mission beyond divisions
In his letter, Leo XIV insists that the path to unity cannot be limited to a simple doctrinal or institutional agreement: it must be rooted in common prayer, charity and the visible witness of faith in everyday life. He invokes the Holy Spirit as a "divine bond of unity" within the Trinity and between believers, an indispensable condition for lasting reconciliation.
THE pope It also challenges each Christian to reflect on their own relationship with God and how they live their faith in the world. The Creed must not remain a mere recited text, but rather a commitment to embodying "the proclaimed truth" in justice, solidarity, and the protection of creation. This is the very essence of a shared mission that transcends historical and cultural differences.
Ultimately, the message of Leo XIV is clear: by returning to the common roots of the Christian faith, summarized in the Nicene Creed, and by opening oneself to the action of the Holy Spirit, Christians have a real chance to overcome the conflictual past to build together a future of peace and visible unity.
Thus, this project of Leo XIV is part of a long and demanding process, based on recalling origins, ecumenical prayer and brotherhood concrete. It rests on the conviction that "the unity of faith" is the key to restoring strength and hope to a world searching for meaning and to Churches divided but called to walk together. This pilgrimage in Türkiye This is the first symbolic and spiritual step.
