In the United States, the Protestant Reformation is perhaps the best known schism in Christianity. The story of how Martin Luther nailed his 95 theses to the door of Castle Church in Wittenberg, Germany dominates our understanding of modern Christianity. Whether the reader supports the ideals of the Protestants or Catholics concerning this fundamental split, it is plain to see that the Protestant Reformation, and the Counter-Reformation it brought on, serves as a fundamental pivot point in the history of Christianity.
This was not the first, or potentially most damaging, schism Christianity has endured. In 1054 Papal legates, led by Cardinal Humbert of Mourmoutiers, traveled to Constantinople and met with Patriarch Michael Cerularius in an attempt to settle some theological differences that had risen between Rome and Constantinople. Though the exact exchange between these two parties is not known, both groups left the initial introduction angry, and this would prove the salt that would not allow the doctrinal wounds to heal. Invested with the authority to excommunicate the Patriarch of Constantinople, Cardinal Hubert did so. His party came into the Haga Sophia while Michael Cerularius celebrated Mass and placed the Papal Bull of Excommunication on the altar before the stunned and enraged Patriarch. Not long after this monumental event Michael excommunicated the Papal legates.
It is important to note that these dueling excommunications were, in fact, leveled towards certain individuals and not the population of the Eastern and Western Empires specifically. It mattered little, however, for the moves were seen as symbolic of the larger problem, namely the ever increasing religious, political, even linguistic, gulf between Rome and Constantinople.
So what was at the heart of this schism? There are innumerable arguments concerning the true source of the split, but I will concentrate today on the theological differences that were, if not the primary reason behind the Great Schism, then certainly the doctrinal reasons used to justify the parting of ways.
