Later this week, Pope Leo XIV begins his first international apostolic visit: a six-day trip to Turkey and Lebanon from November 27 to December 2. At the center of that journey is his stop in Nicaea—today the town of İznik—where the first ecumenical council (325 A.D.) set down the Nicene Creed, the profession of faith that has united Christians for seventeen centuries. Pope Francis had hoped to make this pilgrimage in May; now, Pope Leo is taking up the mantle.

We’re re-running our deep dive episode on Nicaea today—originally published before Pope Francis’ death. It explores the history of Nicaea and its ongoing importance for Christians, particularly in working toward a common Easter date.

In the show’s introduction, producer Ricardo da Silva, S.J., updates listeners on Pope Leo’s new document on Christian unity, released to commemorate the council’s anniversary, and on a recently issued doctrinal note on monogamy from the Dicastery for the Doctrine of the Faith.

In the deep dive, you’ll hear from:

Aristotle (Telly) Papanikolaou, Professor of Theology and the Archbishop Demetrios Chair in Orthodox Theology and Culture at Fordham University 

John Chryssavgis, deacon of the Greek Orthodox Archdiocese of America and archdeacon of the Ecumenical Patriarchate

Donald Bolen, Archbishop of Regina in Canada and a member of the Vatican Dicastery for Promoting Christian Unity 

Married professors Ben Hohman, a Roman Catholic, and Claire Koen, an Eastern Orthodox Christian

Sandra Beardsall, Professor Emerita of Church History and Ecumenics at St. Andrew’s College in Saskatoon, Canada, an ordained United Church minister and a member of the World Council of Churches’ Faith and Order Commission

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