I believe in one God, Father Almighty, Creator of heaven and earth, and of all things visible and invisible. And in one Lord Jesus Christ, the only-begotten Son of God, begotten of the Father before all ages; Light of Light, true God of true God, begotten, not created, of one essence with the Father through Whom all things were made. Who for us men and for our salvation came down from heaven and was incarnate of the Holy Spirit and the Virgin Mary and became man. He was crucified for us under Pontius Pilate, and suffered and was buried; And He rose on the third day, according to the Scriptures. He ascended into heaven and is seated at the right hand of the Father; And He will come again with glory to judge the living and dead. His kingdom shall have no end. And in the Holy Spirit, the Lord, the Creator of life, Who proceeds from the Father, Who together with the Father and the Son is worshipped and glorified, Who spoke through the prophets. In one, holy, catholic, and apostolic Church. I confess one baptism for the forgiveness of sins. I look for the resurrection of the dead, and the life of the age to come. Amen.
Nicea 1 The First Ecumenical Council in Nicea, A.D. 325, with 318 holy fathers participating. This Council, commemorated separately on May 29 (and on the Seventh Sunday after Easter), convened to refute the heresy of Arius against the Son of God.
Constantinople I Formulated the Second Part of the Creed, defining the divinity of the Holy Spirit The Second Ecumenical Council was in Constantinople, A.D. 381, with 150 holy fathers attending. This Council, commemorated separately on May 22, convened to refute the heresy of Macedonius against God, the Holy Spirit. Ephesus The Third Ecumenical Council in Ephesus, 431 A.D. with 200 holy fathers participating. This Council is commemorated separately on September 9. This Council refuted the heresy of Nestorius against Christ as the Incarnate Word of God and Mary as Theotokos.
Chalcedon The Fourth Ecumenical Council in Chalcedon, A.D. 451, with 630 holy fathers participating. This Council is commemorated separately on July 16. This Council refuted the Monophysite heresy and rightly defined Christ as Perfect God and Perfect Man in One Person
Constantinople II The Fifth Ecumenical Council assembled in Constantinople in A.D. 553, with 160 holy fathers participating. This Council is commemorated separately on July 25. This Council refuted the heresy of Origen and reconfirmed the Doctrines of the Trinity and of Christ.
Constantinople III The Sixth Ecumenical Council in Constantinople met in A.D. 680-81, with 170 holy fathers participating. This Council is commemorated separately on January 23. This Council refuted the Monothelite heresy and affirmed the True Humanity of Jesus by insisting upon the reality of His human will and action.
Nicea II The Seventh Ecumenical Council which was convened in A.D. 878, with 367 holy fathers participating. This Council is not commemorated at this time but is commemorated separately on October 11. Affirmed the propriety of icons as genuine expressions of the Christian Faith.
At these Councils, through the operation of the Holy Spirit, all these heresies were condemned and the Faith of Orthodoxy was defined and confirmed for all time.