MICHAEL CERULARIUS. — Greek Patriarch of Constantinople (1043–58), born there at the beginning of the 11th century, famous for the definitive schism from the Roman See. His career was owed to Constantine IX Monomachus, with whom, still a layman in 1040, he had taken part in a political conspiracy; he was poorly educated and remained all his life of a violent character. Towards Latins he was extremely intolerant and as early as about 1053 he closed their churches and monasteries in Constantinople; his opposition grew when the Byzantine captain (catapan) of Lower Italy, Argyrus, a Catholic, sought to establish an alliance with Pope Leo IX against the Normans threatening Lower Italy. Michael feared that this policy would increase the religious authority of the Pope. He therefore endeavoured to stir up a religious controversy, with speeches and with an anti-Roman letter which he suggested to the metropolitan Leo of Achrida (v.). The Emperor did not support these attacks, but induced the Patriarch to send the Pope a pacific letter, the contents of which did not fully satisfy the Bishop of Rome. The latter, to clarify the religious situation at Constantinople, which had been harbouring the schism for more than two decades, and to facilitate a political alliance with the Emperor against the Normans, who in June 1053 had won a victory over Argyrus at Siponto and over the Pope at Civitate, sent a papal legation to the Byzantine court.
Its head was Cardinal Humbert of Silva Candida (v.); associated with him were Frederick (the future Pope Stephen X), chancellor, and Peter, Archbishop of Amalfi. These three prelates set out in January 1054 and reached Constantinople towards the end of March. The relations of the papal embassy with the Byzantine Emperor were always good. The Patriarch, however, from the first and only audience granted to the legates, showed coldness which soon turned to open hostility. Indeed, the Patriarch broke off relations with the legates and induced the learned monk Nicetas Stethatus to engage in a controversy against the Latins, who had brought among the Greeks certain apologetic writings of unfortunately harsh style against Leo of Achrida and his anti-Latin companions. The temporary retraction of Nicetas, in the dispute favourable to the Latins in the monastery of Studios on 24 June 1054, did not improve matters; on the contrary, Michael Cerularius forbade the legates to celebrate Mass in Greek churches and stirred up the people against them. The legates, seeing the uselessness of their attempts to reconcile the Patriarch with Rome, placed a document of excommunication upon the altar of Hagia Sophia during the solemn liturgy of 16 July 1054. The excommunication struck Leo of Achrida, the sacellarius, who had irreverently trodden upon the Latin Eucharist. It is to be noted, however, that this excommunication was not drawn up in the form of a papal bull; indeed it was promulgated after the death of Pope Leo IX. In his turn Michael Cerularius hurled an anathema against the legates on 21 and 26 July, sent out an encyclical to the East, and probably composed the book Panoplia. The Patriarch Peter of Antioch was not pleased with the violent polemic of his colleague, but could not reduce him to peaceful sentiments. Michael Cerularius again interfered in politics in 1057 and 1058, and ended his agitated life in the disturbances on 8 November 1058. His name remains connected with the consummation of the Byzantine schism, which had begun several decades earlier.