Constantinople, First Council of, 381, second ecumenical council. It was convened by Theodosius I, then emperor of the East and a recent convert, to confirm the victory over Arianism. The council drew up a dogmatic statement on the Trinity and defined Holy Spirit as having the same divinity expressed for the Son by the Council of Nicaea 56 years earlier. That statement has been lost, but the work of the council established the orthodox teaching of the Trinity as it is held today. The traditional belief ascribing the present form of the Nicene Creed (see creed) to this council has been questioned by modern scholars. The council condemned all varieties of Arianism along with a new heresy, Apollinarianism. The sessions, which were attended only by bishops of the East, lasted two months. Gregory of Nazianzus was reinstated as bishop of Constantinople and then made president of the council when its first president, Meletius of Antioch, died. Gregory resigned when the council disregarded his wishes and elected Flavian of Antioch as Meletius' successor at Antioch.