History of the Catholic Church
During the 11th century, the East–West schism divided Christianity  forever. It started with a dispute on whether Constantinople or Rome held jurisdiction over the church in Sicily. This led to mutual excommunications in 1054. The Western (Latin) branch of Christianity has since become known as the Catholic Church. The Eastern (Greek) branch became known as the Orthodox Church. The Second Council of Lyon (1274) and the Council of Florence (1439) both failed to heal the schism. Some Eastern churches have since reunited with the Catholic Church, and others claim never to have been out of communion with the pope. Officially, the two churches remain in schism, although excommunications were mutually lifted in 1965.