Humbert of Moyenmoutier, the Cardinal-Bishop of the suburbicarian see of Silva Candida from 1051 until his death in 1061, is best known today for his famous 1054 excommunication of the Byzantine patriarch of Constantinople. This action is popularly understood to be the start of the division that still exists today between the Eastern Orthodox and the (Western) Catholic Churches. Humbert did not approach the conflict as a politician or as a canonist but rather as a monk and an ardent disciple of his own liturgical tradition.
This work falls into two halves. The first examines Humbert’s life in the Abbey of Moyenmoutier and his work under Popes Leo IX, Victor II, Stephen IX, and Nicholas II. The second addresses each of the major liturgical topics in the 1054 conflict in turn: the use of azymes, the Sabbath fast, clerical marriage, the consumption of unclean foods (blood), and the alleluia. This dissertation concludes first, that Humbert was strongly influenced by the preoccupations of the reformation movement in the Western Church and the tradition of Latin liturgical exegesis in his approach to the Byzantine rite, and second, that his evaluation of these liturgical topics is nuanced and well-informed, if strongly biased in favor of his own tradition.