Cathedrals:

The name of Ecumenical councils is given to councils that are convened on behalf of the entire Christian Church to resolve questions about the truths of the doctrine and are recognized by the entire Church as the undisputed sources of Canon law. There are only seven Ecumenical councils, which would be accepted by both the Western and Eastern Christian churches, although Catholics continue to assemble their councils, calling them Ecumenical, to this day (there are already 21). The need to convene councils was due to the accumulation of contradictions that require resolution at the level of making additional dogmas and condemnation of illegal points of view that distort the Christian doctrine.

The first Ecumenical Council, held in Nicaea (and therefore sometimes referred to as the Nicene Council), was convened by the Emperor Constantine I (306-337) in 325 in order to condemn the point of view of the Alexandrian Bishop Arius. The fact is that the position of Orthodox Christianity at this point was to recognize the equality of God and his son Jesus. Arius rejected such equality, appealing to simple common sense that the son is never equal to the father. The son of God is not a son in the essential sense of the word, but a spiritual offspring of God. The relationship of the blood bond between them was introduced just to emphasize the subordinate attitude of Jesus towards God the father. Arianism, which by this time had found numerous followers in the middle East and North Africa, was anathematized as heresy, because it denied the dogma of the consubstantiality of the Son to the Father. In addition, the Council of Nicaea formulated the first seven provisions of the Creed (a set of dogmatic rules that set out the essence of the Christian faith) and formed a hierarchy of the main dioceses. The Roman, Alexandrian, Antioch, and Jerusalem churches were recognized as the most revered and respected because of their long-standing origins and unshakable spiritual authority.

The second Ecumenical Council, which met in 381 in Constantinople, finally approved the Creed, making there the five remaining provisions. Representatives of the Christian clergy, gathered from all parts of the Roman Empire, had to make every effort to refute the claims of the followers of Arianism, who considered the Holy Spirit to be a product exclusively of Jesus. The Trinitarian dogma formulated at the second Ecumenical Council included provisions on the equality of the Father, the Son, and the Holy spirit, as well as on the descent of the Holy spirit from the Father and the Son. Some changes have taken place in the administrative structure of the Christian Church. The second most important Church after the Roman one was declared Constantinople, which was the result of the strengthening of the Eastern part of the Roman Empire with its capital in Constantinople and the corresponding increase in the importance of the Bishop of Constantinople.

The third Ecumenical Council was held in Ephesus in 431 under the sign of disputes about the nature of Jesus. The fact is that the Bishop of Constantinople Nestorius defended the view that Jesus was originally born a man, and his communion to the divine essence took place only at the time of baptism. As a result of long disputes between representatives of various Christian communities, the teaching of Nestorius and his followers (later known as Nestorianism) was condemned as heresy, and the dogma was put forward the statement that Christ was by nature a God-man, so there could be no separate human nature. Both the divine and human natures of Christ form a single Hypostasis (Christological dogma).Despite official condemnation at the Council of Ephesus, Nestorianism continued to spread actively to the East, gaining a large number of followers among the Turks and Mongols. Nestorianism supporters formed a significant part of the Mongol tribes as early as the thirteenth century, when the gradual displacement of Christianity from Asia by the growing power of Islam began.