In July 1054 Cardinal Humbert of Silva Candida, legate of a pope who had in fact died in April, strode into Hagia Sophia during the liturgy and laid on the altar a bull excommunicating the Patriarch Michael Cerularius and his associates; the patriarch's synod promptly anathematized the legates in return. Historians are unanimous that the moment was less decisive than its legend, the excommunications were personal, not of churches, arguably invalid, and East and West continued to interact for centuries, but symbols do not consult historians, and the exchanged anathemas of 1054 hardened into the accepted birthdate of the schism between Rome and Orthodoxy. What makes the story singular is its ending.
On 7 December 1965, in simultaneous ceremonies in Rome and Istanbul, Pope Paul VI and Ecumenical Patriarch Athenagoras I issued a Joint Declaration removing the sentences: the two churches regretted the offensive words on both sides, and consigned the excommunications of 1054 to oblivion, erasing them, the text says, from the memory and the midst of the Church. The gesture dissolved no doctrinal difference, and both sides said so plainly; the schism's substance, papal primacy above all, remains in negotiation six decades later. But as an event in the grammar of anathema it is nearly unique: the most famous curses in Christian history were formally unsaid, establishing that what a church binds with a formula it can, with sufficient penitence and daring, loose again.