The East-West Schism

Pope Leo IX's actions in 1054 (through his delegate Cardinal Humbert, actually) were the catalyst for the great East-West Schism between the Western and Eastern churches, but only because differences had been building for a long time.

Some of the difficulties between the two rose from cultural differences. The West was influenced by Roman law, while the East had Greek philosophy at its base, leading to much more vigorous intellectual debate about dogma and doctrine and misunderstandings between the two.

Also, the West considered itself superior from the start as the seat of Peter, and so did not discuss changes with its Eastern counterpart before making changes like adding the phrase "and from the Son" to the Nicene Creed, established at the First Council of Constantinople in 381. This phrase, Filioque in Latin, created a huge controversy over whether the Son of God was co-equal with the Father as a source of the Holy Spirit. The 879–880 Council of Constantinople (Eastern Orthodox, as opposed to the Fourth Council of Constantinople Roman that took place a decade earlier) rejected the phrase Filioque.

The Eastern Church also believed in what is now called eucharistic ecclesiology (or more recently holographic ecclesiology), the idea that each bishop is the successor of St. Peter, equal to all other bishops, and the head of his own diocese, and that all these churches constituted the whole Church. The Roman West followed universal ecclesiology, a more "feudal" system in which all bishops were beholden to the hierarchy above them, leading up to the pope. The Orthodox Church does not accept the idea of papal authority being supreme, believing in a more collaborative or collegial relationship between all dioceses.

Although the Fourth Council mentioned above affirmed the value of images of god and saints for veneration, the Eastern policy earlier had promoted iconoclasm, based on Moses' 3rd Commandment against "graven images." The West had never been opposed to such things, but there was a strong current against it in the East, which drew a line between veneration ("respect"), and worship of an image.

With these in the background, we come to Patriarch Michael I Cerularius, who adds to the differences the use of unleavened bread in the West for the Eucharist. The Eastern argument is that yeast causes bread to rise and that is a better symbol for the Resurrection. The West uses unleavened bread because that is what Jesus would have used at the Last Supper, being a Seder.

These were already points of contention in 1054, so when Pope Leo IX tried to tell Patriarch Michael to fall in line because the Donation of Constantine said he should, the East had had enough.

Of course, differences continued to be created, as both sides did their best to understand the world. One of them that started to appear a century after the East-West Schism started was the idea of Purgatory. I'll talk about that next time.