schism

Formal split over a doctrinal difference between religious believers, as in the final schism between the Roman Catholic and Eastern Orthodox churches in 1054; the Great Schism (1378–1417) in the Roman Catholic Church; the separation of the Old Catholics who rejected the doctrine of papal infallibility in 1879; and the schism over the use of the Latin Tridentine mass in 1988.

The first major split in the Christian church developed with the breaking up of the Roman Empire into Eastern and Western parts from AD 395. Argument developed between the pope, the head of the church in Rome, and the patriarch, the head of the church in Constantinople, capital of the Eastern Roman Empire, or Byzantine Empire. The two main points of disagreement involved the position of the pope and his prerogatives, and the doctrine known as the Filioque clause, in the Nicene Creed.

In 1054, the papal legate Cardinal Humbert excommunicated the patriarch of Constantinople, Michael Cerularius, for obstructing an alliance between the Byzantine emperor and the pope. Cerularius retaliated by excommunicating the cardinal and so caused the final schism between the Eastern (Orthodox) Church and the Western (Roman Catholic) Church.