May 20, 325: Emperor Constantine convenes the first Ecumenical Council in Nicaea (now Iznik), Bithynia, to discuss Arianism, a heresy arguing that Christ was subordinate to God the Father. "I entreat you," Constantine said at the opening of the Council of Nicea, "to remove the causes of dissension among you and to establish peace." The council attempted to resolve the bitter conflict by anathematizing Arius (Arianism's founder) and ordering the burning of all his books, but ...