Final answer:
The Eastern Orthodox Church was established following the Great Schism of 1054, which represented the major division between the Eastern and Western churches, over differences in practice, culture and leadership. Attempts at reconciliation failed, and theological differences were solidified over subsequent years and councils.
Step-by-step explanation:
The Eastern Orthodox Church was formed following the Great Schism of 1054, which constituted a major split between the churches of the East and the West. This split was both cultural and theological. Western Christianity, which became the Roman Catholic Church, used Latin language and enforced celibacy for its clergy, with the Pope as the singular authoritative figure. In contrast, the Eastern Orthodox Church used Greek, permitted married priests, and saw not just the Pope, but other patriarchs as leaders.
In the Middle Ages, five episcopal sees were influential - Jerusalem, Antioch, Alexandria, Rome, and Constantinople. However, by the 10th century, only Rome and Constantinople were not under Muslim control, raising their importance. The Western church, led by the Pope in Rome, and the Eastern Church, led by the Patriarch of Constantinople, began to differ significantly, leading to the Great Schism.
Efforts at reconciliation, such as the call for help from Byzantine ruler Alexios I to Pope Urban II, were unsuccessful. The ecclesiastical differences were further deepened by historical incidents like the Council of Nicaea in 325 which aimed at defining theological aspects of Christianity.
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