East–West Schism

The East–West Schism, also called the Great Schism and the Schism of 1054, was the break of communion between what are now the Eastern Orthodox and Roman Catholic churches, which has lasted since the 11th century. It is not to be confused with the Western Schism (which is also sometimes called the "Great" Schism).

The ecclesiastical differences and theological disputes between the Greek East and Latin West pre-dated the formal rupture that occurred in 1054. Prominent among these were the issues of the source of the Holy Spirit, whether leavened or unleavened bread should be used in the Eucharist, the Bishop of Rome's claim to universal jurisdiction, and the place of the See of Constantinople in relation to the Pentarchy.

In 1053, the first step was taken in the process which led to formal schism: the Ecumenical Patriarch of Constantinople Michael I Cerularius ordered the closure of all Latin churches in Constantinople, in response to the Greek churches in southern Italy having been forced either to close or to conform to Latin practices. According to the historian J. B. Bury, Cerularius' purpose in closing the Latin churches was "to cut short any attempt at conciliation".

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