Vatican City: As the global Church marks the momentous 1,700th anniversary of the First Council of Nicaea, Fr. Elias D. Mallon, Ph.D., offers a thoughtful reflection on how this landmark event set in motion the long and evolving journey of ecumenism—a quest for Christian unity that continues to unfold today.
The Council of Nicaea, convened in the city of Nicaea (modern-day İznik, Türkiye) from May to July 325 A.D., was the Church’s first gathering labeled as “ecumenical.” The concept of what “ecumenical” means has undergone profound transformation since that early assembly. Over seventeen centuries, the Christian world has witnessed both tremendous growth and painful divisions, shaping the course of faith and history alike.
This pivotal council convened against a backdrop of major upheaval in the Greco-Roman world. The late third and early fourth centuries were marked by the brutal persecutions under Emperor Diocletian, who sought to crush Christianity and consolidate his vast empire’s fragile unity. After Diocletian’s abdication, Constantine the Great rose to power, attributing his military successes to the Christian God—a faith that soon became favored across the empire.
Constantine’s reign blurred the lines between political and religious authority, as he prioritized peace and unity in both realms. Yet the Christian community itself was far from unified, challenged by theological disputes like those stirred by Arius, whose denial of Christ’s full divinity threatened the Church’s cohesion. It was Constantine himself, though not yet baptized, who called and presided over the Council of Nicaea—an act that remains a theological and philosophical puzzle, symbolized in the differing artistic portrayals of the event in Eastern and Western Christian traditions.
The evolving meaning of “ecumenical” councils must be understood in the context of ongoing divisions within Christianity. Since the Great Schism of 1054, which formally separated the Catholic West and Orthodox East, each tradition has questioned the ecumenicity of councils held without their participation. This division underscores a key tension in the very idea of what an ecumenical gathering entails—whether it means full communion or a hopeful step toward it.
By the 19th century, the persistent fragmentation of Christianity began to be seen as a scandal to the faith’s credibility. This sparked a movement toward ecumenism, accelerated by the trauma of two world wars and culminating in initiatives like the World Council of Churches (founded 1948) and the Catholic Church’s commitment through Vatican II’s 1964 decree, Unitatis redintegratio. The meaning of “ecumenical” shifted again—from gatherings of fully united believers to dialogues among divided Christians seeking reunion.
Today’s ecumenical landscape is shaped by this historical tension and hope. The collaborative friendship between Pope Francis and Ecumenical Patriarch Bartholomew exemplifies a new form of ecumenism—one where deep theological differences remain acknowledged but do not preclude mutual respect, affection, and cooperation. Their annual exchanges and joint celebrations affirm a unity that transcends doctrinal disagreements, highlighting that perfect unity may be a future hope rather than an immediate prerequisite for fellowship.
As the Church commemorates this 1,700-year milestone, it recognizes that Nicaea was not merely a distant historical event but a living impetus for ongoing reconciliation. Pope Francis’ recent message for the 2024 Constantinople visit framed the anniversary as a call to witness the “growing communion” among all baptized Christians, a concrete sign of unity already present, even amid imperfection.
Nicaea’s legacy thus invites Christians to embrace a renewed vision of unity—not as a static achievement but as a dynamic journey. This anniversary encourages the faithful to build on the foundations laid nearly two millennia ago, moving toward a future where the Church’s many branches may once again flourish as one body in faith, hope, and love.