What the Ecumenical Council of Churches, or World Council of Churches were and the kind of impact they have had on Christianity and world history.
Ecumenical?
'Ecumenical' comes from Greek, where it means 'the inhabited world.' For us, that means everywhere there are people. The ecumenical councils, though, were held from the fourth century, so that view wasn't exactly up-to-date. At that time, Christianity had only spread over the Roman Empire and the Roman Empire was considered to be the only civilized place in the world. When they spoke of an ecumenical council, what they meant was that Christians from throughout the Roman World were represented. Later, after the Empire was gone, ecumenical came to mean true Christians wherever they were found.
Since all of the world's Christian leaders were present, their decisions were considered infallible, meaning you couldn't really question them. The thinking was that if so many ecclesiastical people could agree on an issue then it had to be the will of God. Because of that, any individual or group that went against an ecumenical council's decision was often excommunicated.
Why Were They Held?
Life for Christians while they were being persecuted (up until about 300 C.E.) was very hard, and the simple fact that they all believed Jesus had been sent by God kept them together. However, once Christianity was accepted by more and more people, things changed. For centuries, people had been hiding and not discussing their interpretations of God and their religion. It was inevitable that different ideas had emerged in different areas. The church recognized that it had to agree on one way of worshiping God.
The First Three
The first two ecumenical councils were the First Council of Nicaea (in 325 C.E.) and the First Council of Constantinople (in 381 C.E.). They fixed a date for Easter, granted the holy sees (which are basically Catholic 'districts') of Rome, Alexandria, Antioch and especially Jerusalem a place of influence in the church, and called the alternate faiths of Arianism and Macedonism heretical. Their focus, though, was in defining exactly what the relationship between God and Jesus was. They decided that the two and the Holy Spirit were just three aspects of the same person and summed it up in the Nicene Creed.
The Council of Ephesus (431 C.E.) condemned Nestorianism, which said that Mary had not given birth to God. After that decision, the Church of the East stopped attending the ecumenical councils. The council also called Pelagianism heretical. Pelagianism was the belief that even with God that people have Free Will. St. Augustine's belief in Predestination was then considered canon from then on.
