Question: "What was the Great Schism?"
Answer: The Great Schism is the title given to the rift that formed in the Church in the eleventh century A.D. This separation led to the "Roman Catholic" Church, hereafter known as the Western Church, and the "Greek Catholic" or "Greek Orthodox” Church, hereafter known as the Eastern Church.
In order to best understand what happened, we need to examine history and the context in which that history occurred. The Church from the fourth century onwards had 5 patriarchs or heads, and each one governed a jurisdictional area or patriarchate. The patriarchates were located in the West in Rome, which spoke Latin, and in the East in Antioch, Alexandria, Jerusalem, and Byzantium, which all spoke Greek.
Wanting to create a new Christian empire, and due to the degree of paganism in Rome, the Emperor Constantine decided to move the capital of the Empire to Byzantium (which was later renamed Constantinople after him). Around this time, and shortly after this move, Germanic tribes began invading across Europe. This invasion had the effect of plunging Europe into what is known as the "Dark Ages." The combination of economic and political turmoil, geographical distances, and linguistic differences created a rift that caused the eventual estrangement of West from East.
Given these factors, it is not surprising that very few Western theologians spoke Greek, and instead wrote and spoke primarily in Latin. They did not have access to, nor could they read, the writings of the Eastern theologians. Because of this, most Western theology was based on a few key Latin theologians, whereas the East had numerous Greek theologians and did not have to focus on any particular theologian's teaching.
The flexibility of the Greek language (it had approximately ten times the vocabulary of Latin) allowed for more expressive and deeper writings. The decline of literacy in the West led to the clergy being the primary teaching authority. This is contrasted with the East where general education and more universities created a literate populace, and thus more lay theologians who played an active role in the church.
The growing list of differences between East and West simply exacerbated the tensions. One of the most striking differences was that as new people were evangelized in the West, they had to use Latin as their liturgical and ecclesiastical language, while looking to Rome for leadership. On the other hand, missionaries from the East translated the Bible into the language of the people. When the new churches in the East became mature, they became self-governing and administratively independent from their mother church. In the West, Rome began to require all clergy to be celibate; whereas, in the East they retained married clergy.
So, while the filioque controversy is often cited as the cause of the Great Schism, with the Eastern and Western bishops excommunicating each other, it was, in fact, only the breaking point. Differences, disagreements, and distance had been laying the foundation for the Great Schism for centuries. The Great Schism was essentially the “forerunner” of the Protestant Reformation, with a refusal to accept the unbiblical concept of the supremacy of Rome at its core.