- 325– 1st Ecumenical Council of Nicaea condemns Arius and clarifies the dogma of Christ’s divinity by expanding Creed’s 2nd stanza
- 381– 1st (Ecum) Council of Constantinople expands 3rd stanza of creed defining the divinity of the Holy Spirit and also condemns Apollinaris’s heresy that Jesus lacked a complete human soul
- 431– Council of Ephesus defines Christ as the incarnate Word of God and proclaims Mary Theotokos (“God-bearer” or “Mother of God”) after deposing Nestorius, Patriarch of Constantinople
- 451– Ecum. Council of Chalcedon defines Christ as having both a divine and a human nature in one person
- 553– 2nd (Ecum) Council of Constantinople confirms christological & trinitarian doctrine against the Nestorians
- 680– 3rd Ecum. Council of Constantinople affirms that Jesus had a truly human will as well as a truly divine will against the Monothelites
- 787– 2nd Ecum Council of Nicaea vindicates the veneration of images
Catholic theologians recognizes a total of 21 Ecumenical councils (there is no officially binding list) the last fourteen of which took place in the West. The Eastern Orthodox recognize only these first seven as being truly ecumenical or universal since they happened before the eastern and western patriarchates were rent by the thousand-year schism which has yet to be healed. For Catholic theologians, a council is deemed ecumenical if it is approved and recognized by the pope to be such. The Orthodox require that a council be approved by the Patriarchs of Rome (the Pope), Constantinople, Antioch, Alexandria, and Jerusalem to be authentically ecumenical. This is known as the theory of the Pentarchy, or government by the five ancient patriarchates. These ancient councils, besides their important doctrinal definitions, also promulgated canons or laws governing the discipline of the churches (e.g., liturgical laws, etc.).