Michael Cerularius

The dispute that produced the excommunications of 1054 was, on its face, about bread. The Latin churches used unleavened bread in the eucharist and the Greek churches used leavened, and Cerularius regarded the Latin practice as a Judaising error that made the sacrament unfit. He closed the Latin churches in Constantinople, and a letter was circulated attacking western usage on that and other points.

Leo IX sent a legation headed by Cardinal Humbert of Silva Candida, a man of comparable temper, to settle the matter. The negotiations went badly from the start, Cerularius refused to meet the legates on terms they would accept, and on 16 July 1054 Humbert and his colleagues walked into Hagia Sophia during the liturgy and laid a bull of excommunication on the altar. A synod under Cerularius excommunicated the legates in return.

Two details matter for what the event actually was. Leo IX had died in April, three months earlier, so the legates were acting on the authority of a dead pope and their commission had arguably lapsed. And the documents excommunicated named individuals, not churches: Humbert's bull anathematised Cerularius and his supporters, and the Greek synod anathematised the legates. Neither side purported to cut off the other communion as a whole, and neither had the standing to do so.

It is natural to read 1054 as the moment the Christian world split in two, and historians of the period generally do not. The evidence is that contemporaries did not experience it that way. Communion between Greek and Latin Christians continued in many places for a long time afterwards; there was no general severance of relations; and the incident attracted little notice outside the immediate parties. The eastern patriarchates of Antioch, Alexandria and Jerusalem were not involved.

What made the separation real was slower and mostly later. The theological differences, over the addition of the filioque to the creed and over the nature of papal authority, were substantive and unresolved. The Norman conquest of the Greek territories in southern Italy pressed Latin usage on Greek populations. And above all, in 1204 an army of the Fourth Crusade sacked Constantinople, desecrated its churches, and installed a Latin emperor and a Latin patriarch for half a century. Greek writers date the breach from that, not from a quarrel between two clerics over bread.

The formal residue of 1054 was cleared in living memory. On 7 December 1965, at the close of the Second Vatican Council, Pope Paul VI and the Ecumenical Patriarch Athenagoras I issued a joint declaration expressing regret for the events and lifting the anathemas of 1054 from the memory of the church. The declaration was careful to say that this removed the sentences of that year and did not by itself restore communion, which remains unrestored.