Ultimately, the cause of the Great Schism of 1054 was a question of who was the highest authority. The underlying reasons why there was a split, however, developed in earliest beginnings of the Church. In those days the Church was never completely unified, and several of the original organizations, such as the Coptic Orthodox and Oriental Orthodox Churches, which date from ancient times, still exist as separate entities. By far, the largest body of the Church was the one centered in Rome, which from ancient times was made up of two main groups of people, one speaking Latin and one speaking Greek.
Latin was the language of the administrative center in Rome. Greek, however, was the original language of much of the New Testament. The linguistic difference was part of a foundation of a split that developed more, and not always for reasons that had anything to do with religious doctrine. Like the Church, the Roman Empire was divided between Latin and Greek areas, and the common understanding of this is skewed.
The date we are accustomed to assign to the fall of the Roman Empire was not actually the date of a sudden destruction of a country. In fact, what happened that year was the abdication of the last emperor of the Roman
Empire of the West, with authority being reunited in the hands of the emperor of the Roman Empire of the East. And in theory, the Roman Empire continued with what we call the Byzantine Empire today, but what called itself the Empire of the Roman People at the time.
For group of people in the East, who considered themselves the rightful administrators of law and Justice, to admit that they had lost control over the West was difficult enough, but in addition to that, the popes were demanding that they acknowledge the spiritual leadership of Rome, with increasing demands for political leadership as well.
When Pope Leo Ill crowned Charlemagne Emperor of the West, in 800, it was not a religious issue, but it was a political issue that made the Greeks very upset. From the Greek perspective, Charlemagne and the Pope were usurping the authority of Empress Irene, who was ruling the empire at the time. When Emperor Michael Ill deposed the Patriarch Ignatius of Constantinople in 858, the Pope, Nicholas l, declared the action illegal and acted on his own authority to return Ignatius to his position. This caused further problems, and this time it was within the Church itself.
In 1014, the Pope again tried to exert authority over the ishops of the East, interfering in a change they were making to the to the Nicene Creed. Right or wrong, this created more strain. The time of continual, simmering resentment continued, as the Popes continued to try to get the Greek bishops to accept the supreme authority of Rome, and the Greek bishops always tried to avoid doing this. Finally, in 1054, a group of legates excommunicated the Patriarch of Constantinople because he would not take an oath to acknowledge the supremacy of the Pope, and he retaliated by excommunicating them. Church Split During Middle Ages By brandyHK