Great Ecumenical Councils

Nicea (325)—Prompted by Constantine; 318 bishops present; denounced Arius and affirmed the full deity of Jesus Christ.

Constantinople (381)—Attended by 150 bishops; affirmed the divinity of the Holy Spirit.

Ephesus (431)—More than 200 bishops attended; presided over by Cyril of Alexandria; defined the personal unity of Christ and declared Mary the Mother of God (theotokos) against Nestorius; also condemned Pelagius.

Chalcedon (451)—Attended by 150 bishops; defined the two natures in Christ (divine and human) against Eutyches.

Other important church councils include the Fourth Lateran Council (1215), Council of Trent (1545–63), First Vatican Council (1869–70), and Second Vatican Council (1962–65).