The Church convened the Council when it was necessary to resolve any controversial issue or problem, to develop a certain general approach or vision. Bishops and representatives of all churches gathered at the Ecumenical Councils. The resolutions adopted at the Council were recorded in the Book of Canons (Rules) and subsequently adopted by the church as teaching.
The predecessor of the Ecumenical Councils was the Apostolic Council, convened by the apostles in 51 and designated in the Bible (Acts 15:1-29).
Seven Holy Ecumenical Councils are recognized by the Orthodox Church as follows:
— Nicene I — 325, against heresy Aria
— Constantinople I — 381, against heresy Macedonia
— Ephesian — 431, against the heresy of Nestorius
— Chalcedonian — 451, against the heresy of the Monophysites
— Constantinople II — 553, «About three chapters»
— Constantinople III — 680—681, against the heresy of the Monothelites
— Nicene II — 787, against the heresy of the iconoclasts.
And the liturgical celebration of the holy fathers of the six Councils is explained by the fact that the Seventh Ecumenical Council was called as such at the Local Council of Constantinople in 879—880, while each of the six was approved by the Ecumenical Council at the next one.
The meaning of the special veneration of the holy fathers of the Ecumenical Councils is that only the Councils had the gift of making infallible and « useful definitions for everyone in the field of Christian faith and church piety in moments of crisis in church history.
The brief summary of the dogmatic theology of the holy fathers of the six Ecumenical Councils is reflected in the first conciliar rule of the Council of Trull (691), which became a continuation of the VI Ecumenical Council (III of Constantinople).
In addition to dogmatic activities, the holy fathers of the Ecumenical Councils developed rules that served to streamline church discipline. The Church never deviates from previous dogmatic definitions, developed church canons and does not replace them with new ones.