Christianity, which began as an obscure sect in Judea, survived and
shaking off its Judaistic roots developed in the cosmopolitan world of
Greco-Roman pagan cults. As it followed its natural path various sorts
of local Christianity factions such as Donatists, Novatians, Paulinists,
Marcionites, Docetists, Montanists, Meletians and Arians and many others
While some of these disappeared without becoming widespread heresies some shook Christianity at its roots. The dissensions which were part of the latter group rose from the concept of worshipping a being who was also a man, a concept which had become more complex by the addition of the third divine element, the Holy Spirit.
By the reign of Constantine the Great (324-37, sole ruler) it had become possible to summon general councils which were called Ecumenical Councils to find answers to such questions. It was believed that if all the bishops came together the Holy Spirit would descend and guide their decisions. The number and sort of participants and the decisions of these meetings, however, would often be decided by the politics of the period, being manipulated by the emperor.
There were seven such Ecumenical Councils before the disagreements between Latin (Western) and Greek (Eastern) Christians prevented the holding of any more councils recognized by the whole Church. Except the last one which dealt with Iconoclasm the main topic of the councils was to answer the questions about the Person of Jesus or the Holy Spirit or to reassert the already defined dogma against heretical views such as Arianism, Monophysitism, and alike.
However, in addition to such major questions, regulations about Church discipline were also made. Apart from these Ecumenical Councils there were some which the Roman Church regards as ecumenical, because the Roman Church believes itself to be the one legitimate Christian communion in the whole world; but these later councils were not attended by the representatives of the Greek Orthodox Churches, and are not regarded by those Churches, nor by the Anglican Church, as having been really ecumenical.
The church as established in the middle east has been established under the concept of unity IE catholic and or ecumenical. For the earliest Christian communities the concept of unity was one were the church communities agreed on a doctrinal understanding of Christianity. A doctrine based on the tradition of unity within the different ancient Christian communities. Unity established in what was taught to the communities by Christ and then his apostles. When various persons or groups within the many ancient Christian communities began to come to odds with innovations or interpretations of the tradition of Christianity the communities set out to clarify the validity of the variation in the comparison to traditional understanding. To establish why this change was to be accepted or rejected. As such was the case of the first council in Jerusalem. The later councils where prompted to clarify tradition and address what was proper and what was improper. Proper being what was established by Jesus Christ and then his apostles, then the Seventy and the clergy of the churches that take their linage directly back to the Apostolic era. Innovations being that which changed the understanding that Christian communities.
Ecumenical Councils Turkey
First Council of Nicaea (325)
First Council of Constantinople (381)
Council of Ephesus (431)
Council of Chalcedon (451)
Second Council of Constantinople (553)
Third Council of Constantinople (680-1)
Second Council of Nicaea (787)