If a single event made the division irreparable it was not 1054 but 1204, when an army of the Fourth Crusade, diverted from Egypt by Venetian interests and Byzantine dynastic politics, stormed Constantinople, sacked it for three days, desecrated Hagia Sophia, carried off relics and treasures that are still in Western churches, and installed a Latin emperor and a Latin patriarch over a Greek population.
Before 1204 the differences were the property of theologians and hierarchs. After it, ordinary Greek Christians had experienced the Latin church as an occupying power, and reunion negotiated by emperors under military pressure, at Lyon in 1274 and at Florence in the fifteenth century, was repudiated by the population and the lower clergy each time. The often-quoted preference for the Turkish turban over the Latin mitre belongs to that mood.
The formal position today is more hopeful than the history. In 1965 Paul VI and the patriarch Athenagoras jointly expressed regret for the events of 1054 and consigned the mutual excommunications to oblivion, and a Catholic pope has since expressed sorrow for the sack of 1204. Theological dialogue continues, and the outstanding questions, papal primacy above all, are precisely the ones the councils of the fifth century had already put on the table. The churches remain out of communion.