Christianity in the 4th century, Constantine I and Christianity, First Council of Nicaea, First seven Ecumenical Councils, Nicene and Post-Nicene Fathers, Athanasius of Alexandria, John Chrysostom, Ambrose, Desert Fathers, Monk, Development of the Christian Biblical canon, Deuterocanonical books, Biblical apocrypha, Antilegomena, Pope Damasus I, Saint Optatus