The split between the Roman Catholic branch and the Orthodox branch of Christianity was due to

The Great Schism of 1054 marked the first major split in the history of Christianity, separating the Orthodox Church in the East from the Roman Catholic Church in the West. Until this time, all of Christendom existed under one body, but the churches in the East were developing distinct cultural and theological differences from those in the West. Tensions gradually increased between the two branches, and finally boiled over into the Great Schism of 1054, also called the East-West Schism.

The Great Schism of 1054 marked the split of Christianity and established the separation between the Orthodox Churches in the East and the Roman Catholic Church in the West.

• Start Date: For centuries, tension increased between the two branches until they finally boiled over on July 16, 1054.
• Also Known As: The East-West Schism; the Great Schism.
• Key Players: Michael Cerularius, Patriarch of Constantinople; Pope Leo IX.
• Causes: Ecclesiastical, theological, political, cultural, jurisdictional, and language differences.
• Result: Permanent separation between the Roman Catholic Church and Eastern Orthodox, Greek Orthodox, and Russian Orthodox Churches. Recent relations between East and West have improved, but to date, the churches remain divided.  

At the heart of the break was the Roman pope’s claim to universal jurisdiction and authority. The Orthodox Church in the East had agreed to honor the pope but believed that ecclesiastical matters should be decided by a council of bishops, and therefore, would not grant unchallenged dominion to the pope.

After the Great Schism of 1054, the eastern churches developed into the Eastern, Greek, and Russian Orthodox Churches, while the western churches formed into the Roman Catholic Church. The two branches remained on friendly terms until crusaders of the Fourth Crusade captured Constantinople in 1204. To this day, the schism has not been wholly mended.

By the third century, the Roman Empire was growing too large and difficult to govern, so Emperor Diocletian decided to divide the empire into two domains—the Western Roman Empire and the Eastern Roman Empire, also known as the Byzantine Empire. One of the initial factors which caused a shifting apart of the two domains was language. The primary language in the West was Latin, while the dominant language in the East was Greek.

The churches in the divided Empire began to disconnect as well. Five patriarchs held authority in different regions: The Patriarch of Rome, Alexandria, Antioch, Constantinople, and Jerusalem. The Patriarch of Rome (the pope) held the honor of “first among equals,” but he did not possess authority over the other patriarchs.

Small disagreements called “little schisms” took place in the centuries leading up to the Great Schism. The first little schism (343-398) was over Arianism, a belief that denied Jesus to be of the same substance as God or equal to God, and therefore not divine. This belief was accepted by many in the Eastern Church but rejected by the Western Church.

Another little schism, the Acacian Schism (482-519), had to do with an argument over the nature of the incarnate Christ, specifically whether Jesus Christ had one divine-human nature or two distinct natures (divine and human). One other little schism, known as the Photian Schism, occurred during the ninth century. The dividing issues centered on clerical celibacy, fasting, anointing with oil, and the procession of the Holy Spirit.

Although temporary, these splits between East and West led to embittered relations as the two branches of Christianity grew further and further apart. Theologically, the East and West had taken separate paths. The Latin approach generally leaned to the practical, while the Greek mindset was more mystical and speculative. Latin thought was strongly influenced by Roman law and scholastic theology, while Greeks comprehended theology through philosophy and the context of worship.

Practical and spiritual differences existed between the two branches. For instance, the churches disagreed on whether it was acceptable to use unleavened bread for communion ceremonies. Western churches supported the practice, while Greeks used leavened bread in the Eucharist. Eastern churches allowed their priests to marry, while Latins insisted on celibacy.

Eventually, the influence of the patriarchs of Antioch, Jerusalem, and Alexandria began to weaken, bringing Rome and Constantinople to the forefront as the two power centers of the church.

Since the main language of the people in the Eastern Empire was Greek, Eastern churches developed Greek rites, using the Greek language in their religious ceremonies and the Greek Septuagint translation of the Old Testament. Roman churches conducted services in Latin, and their Bibles were written in the Latin Vulgate.

During the eighth and ninth centuries, controversy also arose regarding the use of icons in worship. Byzantine Emperor Leo III declared that the worship of religious images was heretical and idolatrous. Many Eastern bishops cooperated with their emperor’s rule, but the Western Church stood firm in support of the use of religious images.

The filioque clause controversy ignited one of the most critical arguments of the East-West Schism. This dispute centered around the Trinity doctrine and whether the Holy Spirit proceeds from God the Father alone or from both the Father and the Son.

Filioque is a Latin term meaning “and the son.” Originally, the Nicene Creed stated simply that the Holy Spirit “proceeds from the Father,” a phrase intended to defend the divinity of the Holy Spirit. The filioque clause was added to the creed by the Western Church to suggest that the Holy Spirit proceeds from both the Father “and the Son.”

The Eastern Church insisted on keeping the original wording of the Nicene Creed, leaving the filioque clause out. Leaders in the East argued loudly that the West had no right to alter the foundational creed of Christianity without consulting the Eastern Church. Furthermore, they felt the addition revealed underlying theological differences between the two branches and their understanding of the Trinity. The Eastern Church thought itself to be the only true and right one, believing Western theology to be based erroneously in Augustinian thinking, which they considered heterodox, which means unorthodox and verging on heretical.

Leaders on both sides refused to budge on the filioque issue. Eastern bishops began accusing the pope and bishops in the West of heresy. In the end, the two churches forbade the use of the other church’s rites and excommunicated one another from the true Christian church.

Most contentious of all and the conflict which brought the Great Schism to a head was the issue of ecclesiastical authority—specifically, whether the pope in Rome held power over the patriarchs in the East. The Roman Church had argued for the primacy of the Roman pope since the fourth century and claimed that he held universal authority over the whole church. Eastern leaders honored the pope but refused to grant him the power to determine policy for other jurisdictions or to alter the decisions of Ecumenical Councils.

In the years leading up to the Great Schism, the church in the East was led by the Patriarch of Constantinople, Michael Cerularius (circa 1000–1058), while the church in Rome was led by Pope Leo IX (1002–1054).

At the time, problems sprang up in Southern Italy, which was part of the Byzantine Empire. Norman warriors had invaded, conquering the region and replacing Greek bishops with Latin ones. When Cerularius learned that the Normans were forbidding Greek rites in the churches of Southern Italy, he retaliated by shutting down the Latin rite churches in Constantinople.

Their longstanding disputes erupted when Pope Leo sent his chief advisor Cardinal Humbert to Constantinople with instructions to deal with the problem. Humbert aggressively criticized and condemned the actions of Cerularius. When Cerularius ignored the pope’s demands, he was formally excommunicated as Patriarch of Constantinople on July 16, 1054. In response, Cerularius burned the papal bull of excommunication and declared the bishop of Rome to be a heretic. The East-West Schism was sealed.

Despite the Great Schism of 1054, the two branches still communicated with each other on friendly terms until the time of the Fourth Crusade. However, in 1204, Western crusaders brutally sacked Constantinople and defiled the great Byzantine Church of the Hagia Sophia.

Now that the break was permanent, the two branches of Christianity became more and more divided doctrinally, politically, and on liturgical matters. An attempt at reconciliation took place at the Second Council of Lyon in 1274, but the accord was flatly rejected by the bishops of the East.

Not until more recently in the 20th century did relations between the two branches improve enough to achieve real progress in healing some of the differences. Dialogue between leaders led to the adoption of the Catholic-Orthodox Joint Declaration of 1965 by both the Second Vatican Council in Rome and a special ceremony in Constantinople. The declaration recognized the validity of the sacraments in the Eastern churches, removed the mutual excommunications, and pronounced a desire for continued reconciliation between the two churches.

Further efforts toward reconciliation have included:

• In 1979, the Joint International Commission for Theological Dialogue Between the Catholic Church and the Orthodox Church was established.
• In 1995, Patriarch Bartholomew I of Constantinople visited the Vatican City for the first time, to join in an inter-religious day of prayer for peace.
• In 1999, Pope John Paul II visited Romania by invitation of the Patriarch of the Romanian Orthodox Church. The occasion was the first visit of a pope to an Eastern Orthodox country since the Great Schism of 1054.
• In 2004, Pope John Paul II gave back relics to the East from the Vatican. This gesture was significant because the relics were believed to have been robbed from Constantinople during the Fourth Crusade of 1204.
• In 2005, Patriarch Bartholomew I, along with other Eastern Orthodox Church leaders, attended the funeral of Pope John Paul II.
• In 2005, Pope Benedict XVI reaffirmed his commitment to work toward reconciliation.
• In 2006, Pope Benedict XVI visited Istanbul at the invitation of Ecumenical Patriarch Bartholomew I.
• In 2006, Greek Orthodox Church Archbishop Christodoulos visited Pope Benedict XVI at the Vatican in the first official visit of a Greek church leader to the Vatican.
• In 2014, Pope Francis and Patriarch Bartholomew signed a Joint Declaration affirming their commitment to seek unity between their churches.

With these words, Pope John Paul II had expressed his hopes for eventual unity: “During the second millennium [of Christianity] our churches were rigid in their separation. Now the third millennium of Christianity is at the gates. May the dawn of this millennium rise on a church which has full unity again.”

At a prayer service marking the 50th anniversary of the Catholic-Orthodox Joint Declaration, Pope Francis said, “We need to believe that, just as the stone before the tomb was cast aside, so, too, every obstacle to our full communion will also be removed. Every time we put behind us our longstanding prejudices and find the courage to build new fraternal relationships, we confess that Christ is truly risen.”

Since then, relations continue to improve, but major issues remain unsolved. East and West may never fully unite on all theological, political, and liturgical fronts.

• The Complete Book of When and Where in the Bible and Throughout History (p. 164).
• Pocket Dictionary of Church History: Over 300 Terms Clearly and Concisely Defined (p. 122).
• The Oxford Dictionary of the Christian Church (3rd ed. rev., p. 1089).
• Pocket History of Theology: Twenty Centuries in Five Concise Acts (p. 60).
• Mending the Great Schism: The Pope Takes a Second Step. Christianity Today, 24(1), 56.