787 AD -- The Seventh Ecumenical Council

The Second Council of Nicaea 
was convoked by Emperor Constantine VI and his mother Irene, under Pope Adrian I, and was presided over by the legates of Pope Adrian; it regulated the veneration of holy images. Between 300 and 367 bishops assisted.

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680 - 681 AD -- The Sixth Ecumenical Council

The Third Council of Constantinople, under Pope Agatho and the Emperor Constantine Pogonatus, was attended by the Patriarchs of Constantinople and of Antioch, 174 bishops, and the emperor. It put an end to Monothelitism by defining two wills in Christ, the Divine and the human, as two distinct principles of operation. It anathematized Sergius, Pyrrhus, Paul, Macarius, and all their followers.

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The Connection ... Between the Popes and the Ecumenical Councils

Notice that the Church's ecumenical councils were presided over by either the Pope or his legate(s).  A council in opposition to the pope is not representative of the whole Church, for it neither represents the pope who opposes it, nor the absent bishops, who cannot act beyond the limits of their authority except through the pope. A council not only acting independently of the Vicar of Christ, but sitting in judgment over him, is unthinkable in the constitution of the Church.

(In fact, such assemblies have only taken place in times of great constitutional disturbances, when either there was no pope or the rightful pope was indistinguishable from antipopes. In such abnormal times the safety of the Church becomes the supreme law, and the first duty of the abandoned flock is to find a new shepherd, under whose direction the existing evils may be remedied.)

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553 AD -- The Fifth Ecumenical Council

The Second Council of Constantinople, with 165 bishops under Pope Vigilius and Emperor Justinian I, condemned the errors of Origen and certain writings (The Three Chapters) of Theodoret, of Theodore, Bishop of Mopsuestia and of Ibas, Bishop of Edessa; it further confirmed the first four general councils, especially that of Chalcedon whose authority was contested by some heretics.

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451AD -- The Fourth Ecumenical Council

The Council of Chalcedon — 150 bishops under Pope Leo the Great and the Emperor Marcian — defined the two natures (Divine and human) in Christ against Eutyches, who was excommunicated.

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431 AD -- The Third Ecumenical Council

The Council of Ephesus, of more than 200 bishops, presided over by St. Cyril of Alexandria representing Pope Celestine I, defined the true personal unity of Christ, declared Mary the Mother of God (theotokos) against Nestorius, Bishop of Constantinople, and renewed the condemnation of Pelagius.

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381 AD -- The Second Ecumenical Council

The First General Council of Constantinople, under Pope Damasus and the Emperor Theodosius I, was attended by 150 bishops. It was directed against the followers of Macedonius, who impugned the Divinity of the Holy Ghost. To the Nicene Creed it added the clauses referring to the Holy Ghost (qui simul adoratur) and all that follows to the end.

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