The First Ecumenical Church Council in Nicea (AD 325)
The first Ecumenical Church Council was convened in 325 by emperor Constantine the Great in an attempt to bring theological peace to the church in the Roman empire. More than three hundred bishops, primarily from the Greek eastern church, met in the imperial palace in Nicea (modern Iznik) from May 20 to June 19. The bishop of Rome did not attend, but sent representatives.
Led by bishop Athansius of Alexandria, the council condemned the teaching of Arianism and wrote the first version of the Nicene Creed. In the creed, all three persons of the Trinity—Father, Son, and Holy Spirit—were declared to be fully equal. The central Greek word of the Nicene Creed is homoousios, meaning “one substance, essence or being.” The creed acknowledges that Jesus was “one essence” with the Father. During the council, Eusebius of Nicomedia (modern Izmir) was the primary bishop supporting Arius, who was an elder of Alexandria, Egypt.