Constantinople was the heart of the Eastern Church.
Constantinople was the heart of the Eastern Church.

The split between the Western and Eastern Christian churches into the Roman Catholic and Eastern Orthodox churches is known as the Great Schism. Even though the date of the official Schism is 1054, the break was centuries in coming and the result of a lack of communication between East and West, cultural differences, power struggles within the Church and theological conflicts.

Cultural Differences

Even before the Great Schism, the Western and Eastern sections of the Church had difficulty communicating. The members of the Western Church used Latin, while the Eastern Church used Greek. This naturally led to misunderstandings and miscommunications. Each side had developed different traditions in the wake of the fall of the Western Roman Empire, which left the Eastern Empire -- now known as Byzantium -- politically isolated. By the 11th century, the Popes had been either ignoring or deriding the Eastern bishops and Byzantine Emperors, and vice-versa, for centuries.

Minor Theological Disagreements

Because of the East and West's isolation from one another, different practices emerged, creating conflict. The Western Church's practice of using unleavened bread to represent the body of Christ during the Eucharist, for example, offended the Eastern Church, which saw it as an "innovation" and contrary to the tradition established by Christ. In the Eastern Church, laity participated in Communion by dipping bread into the cup of Christ; this was forbidden to the laity in the West. The Eastern Church did not believe in the immaculate conception of Mary and allowed their priests to marry. None of these differences, however, were direct causes of the Schism.

Power of the Pope

The power of the Pope was extremely offensive to the Eastern bishops. Traditionally, the Church had five patriarchs, or founding bishop seats: Rome, Alexandria, Antioch, Jerusalem and Constantinople. It was agreed that the Pope would hold the position of "first among equals" with the other patriarchs by virtue of the fact that he was the successor to St. Peter. In the view of the Western Church this meant the Pope was infallible and had absolute authority. When the Pope tried to exercise his authority over the other four patriarchs, it started a movement to break with Rome in the Eastern Church.

Filioque Clause

The final conflict in the East-West ecumenical unity came in the form of the filioque clause, which is stated in the Nicene Creed. Filioque is a Latin phrase that means "and from the Son," referring to the Holy Spirit originating from both God and Jesus in the Holy Trinity. Originally, the Creed read that the Spirit proceeded from God alone. The filioque had been hotly debated in the Church for centuries, but the Western Church adopted it without ecumenical council, most particularly without consulting the Eastern Church, which believed it to be doctrinally unsound. When the Eastern Church found out about the filioque, Patriarch Michael I excommunicated Pope Leo IX, and the latter returned the favor, making the break between the churches official.