The East-West Schism, or Great Schism, divided Chalcedonian Christianity into Western (Latin) and Eastern (Greek) branches, i.e. Western Catholicism and Eastern Orthodoxy. Though normally dated to 1054, the East-West Schism was actually the result of an extended period of estrangement between Latin and Greek Christendom. The primary causes of the Schism were disputes over papal authorityPope Leo IX claimed he held authority over the four Eastern patriarchsand over the insertion of the filioque clause into the Nicene Creed by the Western Church. Eastern Orthodox today claim that the primacy of the Patriarch of Rome was only honorary, and that he has authority only over his own diocese and does not have the authority to change the decisions of Ecumenical Councils. There were other, less significant catalysts for the Schism, including variance over liturgical practices and conflicting claims of jurisdiction.
The Church split along doctrinal, theological, linguistic, political, and geographic lines, and the fundamental breach has never been healed. It might be alleged that the two churches actually reunited in 1274 (by the Second Council of Lyon) and in 1439 (by the Council of Basel), but in each case the councils were repudiated by the Orthodox as a whole, on the grounds that the hierarchs had overstepped their authority in consenting to reunification. Further attempts to reconcile the two bodies have failed.
* Byzantium: The Great Schism By Bp. Kallistos Ware
* Catholic Encyclopedia article, representing a Roman Catholic view * In Our Time page with link to online talk
* OrthodoxWiki: Great Schism