On July 16, 1054, Patriarch of Constantinople Michael Cerularius was excommunicated from the Christian church based in Rome, Italy. Cerularius’s excommunication was a breaking point in long-rising tensions between the Roman church based in Rome and the Byzantine church based in Constantinople (now called Istanbul). The resulting split divided the European Christian church into two major branches: the Western Roman Catholic Church and the Eastern Orthodox Church. This split is known as the Great Schism, or sometimes the “East-West Schism” or the “Schism of 1054.”

The Great Schism came about due to a complex mix of religious disagreements and political conflicts. One of the many religious disagreements between the western (Roman) and eastern (Byzantine) branches of the church had to do with whether or not it was acceptable to use unleavened bread for the sacrament of communion. (The west supported the practice, while the east did not.) Other objects of religious dispute include the exact wording of the Nicene Creed and the Western belief that clerics should remain celibate.

These religious disagreements were made worse by a variety of political conflicts, particularly regarding the power of Rome. Rome believed that the pope—the religious leader of the western church—should have authority over the patriarch—the religious authority of the eastern church. Constantinople disagreed. Each church recognized their own leaders, and when the western church eventually excommunicated Michael Cerularius and the entire eastern church. The eastern church retaliated by excommunicating the Roman pope Leo III and the Roman church with him.

While the two churches have never reunited, over a thousand years after their split, the western and eastern branches of Christianity came to more peaceable terms. In 1965, Pope Paul VI and Patriarch Athenagoras I lifted the longstanding mutual excommunication decrees made by their respective churches.

Today, the two branches of Christianity remain distinct expressions of a similar faith. Roman Catholicism is the single largest Christian denomination, with more than a billion followers around the world. Eastern Orthodoxy is the second-largest Christian denomination, with more than 260 million followers. Eastern Orthodoxy includes national churches, such as the Greek Orthodox Church and Russian Orthodox Church.

authority
Noun

person or organization responsible for making decisions.

Catholic
Adjective

having to do with the Christian denomination with the Pope as its leader.

ceremony
Noun

activities to celebrate or commemorate an event.

Christianity
Noun

religion based on the teachings of Jesus of Nazareth.

communion
Noun

Christian sacrament commemorating the death of Jesus Christ with bread and wine.

conflict
Noun

a disagreement or fight, usually over ideas or procedures.

denomination
Noun

branch of a church or larger spiritual faith.

Eastern Orthodox
Noun

loose affiliation of several Christian denominations (including Russian Orthodox, Greek Orthodox, etc.) which follow early church hierarchy.

excommunicate
Verb

to cut off or expel from a church.

faction
Noun

group within a larger group.

patriarch
Noun

highest-ranking bishop in Eastern Orthodox, Oriental Orthodox, the Catholic Church, and the Assyrian Church of the East.

pope
Noun

leader of the Catholic Church.

practical
Adjective

useful or easy to use.

schism
Noun

split or separation.

sever
Verb

to separate or cut away.

spiritual
Adjective

having to do with religion or faith.

unleavened
Adjective

having to do with baked goods lacking a substance that causes them to expand or rise.

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