IZNIK, Turkey — On the second day of his inaugural foreign trip, Pope Leo XIV visited the site where early Christian leaders met 1,700 years ago for the First Council of Nicaea, the gathering that produced the creed still spoken in churches today.
The first American pope prayed alongside Ecumenical Patriarch Bartholomew, the spiritual leader of the world’s Eastern Orthodox Christians, amid the archaeological ruins of the lakeside church where bishops met in 325 to resolve divisions threatening to tear the early Church apart.
“We must strongly reject the use of religion for justifying war, violence, or any form of fundamentalism or fanaticism,” Pope Leo said at the shore of tranquil Iznik Lake. “Instead, the paths to follow are those of fraternal encounter, dialogue and cooperation.”
Pope Leo has used the trip to press for unity — among Christian denominations and among other religions and communities. In a speech alongside Turkish President Recep Tayyip Erdogan, the pope warned that the division and polarization seen in the world today is placing the very future of humanity at stake.
Emperor Constantine convened the First Council of Nicaea, bringing bishops from across the Roman Empire to resolve a doctrinal crisis about Jesus’ relation to God. Christians had endured persecution for some 250 years until Constantine’s decision allowed believers to worship openly across the empire. Constantine saw a unified Church as essential to stabilizing an empire emerging from civil war.
The fiercest dispute came from Arius, an Alexandrian priest who argued that Jesus, though exalted, was the highest created being and not equal to God. The council rejected his teachings and affirmed that Jesus is “of one substance” with the Father — language that forms the basis of the creed recited by Catholics today, beginning, “I believe in one God, the Father almighty …”.
The exact location of the council was discovered about 11 years ago, when aerial photographs of Lake Iznik revealed ruins that had been under about eight feet of water, Turkish archaeologist Mustafa Sahin told NPR. Locals know the ruins well; in low water, swimmers sometimes rest on the stones. As the shoreline receded, the basilica’s full footprint — its apse and dozens of graves — came to light on dry land.
The Church remained largely united until the Great Schism of 1054, which split Catholic and Eastern Orthodox Christianity over theological disputes and power struggles between Rome and Constantinople.
At the historic site on Friday, Pope Leo XIV and Patriarch Bartholomew held a joint silent prayer over the exposed ruins. Ahead of the anniversary, the pope released an apostolic letter emphasizing the creed as a “common heritage of Christians,” written when “the wounds inflicted by the persecutions of Christians were still fresh.”
On Saturday the pope and the patriarch will sign a joint declaration in a modern show of unity.