Second Ecumenical Council (Constantinople 381)
It was in Constantinople, year 381, that this Council was called to by pope Damian and King Theodoritos I the Great, to condemn Makdonios the Arian, whose new heresy denied the divinity of the Holy Spirit. 150 Eastern Catholic bishops formed the Council, faced by some 36 heretic bishops who had followed Makdonios, and who left the Council during its first meeting. The fathers of Council condemned the heresy of Makdonios, him and his followers, and affirmed that the Holy Spirit is God, equally to the Father and the Son. They added to the Nicean Creed, after the words that say: “and we believe in the Holy Spirit”, the following: “Life giving God, who proceeds from the Father and the Son, and worshiped and glorified with the Father and the Son.”
Then they sent the decisions of the Council to Pope Damian, who called for another Council in Rome in the year 382. Another 150 Western bishops attended it and confirmed what the Eastern bishops had decided in Constantinople, condemning the heresy of Makdonios. Finally the pope confirmed the decision by his apostolic faculty, and therefore this Council became ecumenical.