Great Schism

In 1054, a quarrel between emissaries of the Roman pope and the patriarch of Constantinople ended in mutual excommunications, an episode traditionally seen as the moment Christianity divided into the Roman Catholic and Eastern Orthodox churches. Historians now stress that the break was neither sudden nor complete in 1054, but the date remains a convenient marker for a split that shaped the religious and political map of Europe for nearly a millennium.

The roots of the division lay in centuries of gradual estrangement. The old Roman Empire had been split into western and eastern halves, and the two regions increasingly differed in language, with Latin dominant in the West and Greek in the East, as well as in politics and culture. Theological disputes added to the distance. The most famous concerned the Latin addition of the word "filioque" to the Nicene Creed, stating that the Holy Spirit proceeds from the Father "and the Son." Easterners objected both to the doctrine and to the fact that the West had altered the creed without a common council. Other differences included the use of unleavened bread in the Eucharist in the West, clerical celibacy practices, and, above all, the extent of the pope's authority. Rome claimed a universal primacy of jurisdiction, while Eastern leaders generally saw the pope as first among equals within a collective leadership of bishops.

The crisis of 1054 grew out of tensions in southern Italy, where Norman expansion threatened Byzantine holdings and where Latin and Greek church practices clashed. Patriarch Michael Cerularius of Constantinople had Latin churches in his city closed, and Pope Leo IX sent a delegation led by Cardinal Humbert of Silva Candida to negotiate. The talks went badly, as both Humbert and Cerularius were uncompromising. In July 1054, Humbert placed a bull of excommunication on the altar of the Hagia Sophia. Cerularius responded by convening a synod that condemned the legates. Notably, Leo IX had died earlier that year, which raises questions about the legates' authority, and the excommunications targeted individuals rather than the whole churches.

For decades afterward, many Christians on both sides did not regard the rupture as final. Contacts continued, and the Crusades brought cooperation as well as friction. Relations worsened sharply, however, after the Fourth Crusade's sack of Constantinople in 1204, which left deep bitterness in the East. Attempts at reunion, notably at the councils of Lyon in 1274 and Florence in 1439, failed to win lasting acceptance among Eastern clergy and laity.

In 1965, Pope Paul VI and Patriarch Athenagoras I formally lifted the mutual excommunications of 1054. The churches remain separate, but the schism's legacy endures in their distinct traditions, and dialogue between them continues today.