The Seven Œcumenical Councils
Nicaea, A.D. 325 (‘The 318 Fathers’)
Constantinople, A.D. 381 (‘The 150 Fathers’)
Ephesus, A.D. 431
Chalcedon, A.D. 451 (‘The 630 Fathers’)
II Constantinople, A.D. 553
III Constantinople, A.D. 680–81
II Nicaea, A.D. 787
Constantinople, A.D. 381 (‘The 150 Fathers’)
Ephesus, A.D. 431
Chalcedon, A.D. 451 (‘The 630 Fathers’)
II Constantinople, A.D. 553
III Constantinople, A.D. 680–81
II Nicaea, A.D. 787
The Orthodox are orthodox because they accept all seven œcumenical councils: the four great councils of the fourth and fifth centuries, and the three later councils of the sixth to eighth centuries.
Hence, church history may be divided into pre-conciliar (the first three centuries), the conciliar (the next five centuries) and post-conciliar (from the ninth century to the present).
Each great council addressed one burning issue
Nicaea: the relation of the Son to the Father.
Constantinople: the deity of the Holy Spirit.
Ephesus and Chalcedon: the relation of the divine to the human nature of Christ.
II Constantinople: condemned Nestorianism, the doctrine that the Christ was not one person but a temporary fusion of the Son of God with the man Jesus, hence that the Virgin Mary has the title ‘Mother of God’ only by courtesy, not literally.
III Constantinople: condemned the heresy that Christ had only a divine operation and a divine will, not a human operation or will.
II Nicaea: the heresy of iconoclasm, which rejected icons on the ground that the divinity of Christ cannot be depicted, by implication denying that Jesus was incarnate as both True Man and True God.