Ecumenical Councils and the Attempts to Reunify Christendom (AD 325–1054)

Between AD 325 and 1054, the Christian Church convened seven ecumenical councils that significantly shaped the theological, liturgical, and administrative framework of Christendom. These councils were convened to address major theological disputes and to define orthodox beliefs, but they also highlighted and exacerbated divisions within the Church. This period, marked by efforts to maintain unity in the face of theological controversies, ultimately culminated in the Great Schism of 1054, which divided the Church into the Roman Catholic and Eastern Orthodox Churches. This article provides a chronological overview of the seven ecumenical councils, their theological outcomes, and their role in both unifying and fragmenting Christendom. It also introduces the long-term issues that led to the Great Schism, including disputes over the filioque clause, papal primacy, and cultural divergences between the Latin West and Greek East.

The First Council of Nicaea was convened by Emperor Constantine to address the Arian controversy, which questioned the divinity of Jesus Christ. Arius, a presbyter from Alexandria, argued that Christ was not co-eternal with God the Father, a position that threatened the unity of the Church. The Council decisively condemned Arianism and affirmed the doctrine of Christ's full divinity by defining Him as “of the same essence” (homoousios) with the Father. The Nicene Creed, which outlined this theological stance, was adopted as a statement of orthodox faith¹. Nicaea also established a framework for Church administration, including the recognition of three key sees: Rome, Alexandria, and Antioch².

This council, convened by Emperor Theodosius I, was called to address remaining Arian factions and clarify the Church's understanding of the Holy Spirit. It affirmed the Nicene Creed while expanding its theology to declare the divinity of the Holy Spirit, asserting that the Holy Spirit “proceeds from the Father” and is worshiped and glorified alongside the Father and the Son³. This council also solidified the primacy of Constantinople, declaring it second in honor only to Rome—a decision that planted the seeds of future disputes between East and West⁴.

The Council of Ephesus was convened to address the Nestorian controversy, which revolved around the nature of Christ and the role of Mary as the Theotokos (“God-bearer”). Nestorius, the Patriarch of Constantinople, argued that Mary should be called Christotokos (“Christ-bearer”) rather than Theotokos, as he believed in a separation between Christ’s divine and human natures. The council condemned Nestorianism, affirmed the title of Theotokos for Mary, and declared Christ as one person with two natures, fully divine and fully human⁵. This decision alienated the Church of the East, leading to its separation from the broader Christian world⁶.

One of the most consequential councils, Chalcedon addressed the Monophysite controversy, which held that Christ had a single, divine nature rather than two natures. The council affirmed the doctrine of the hypostatic union, declaring that Christ is fully divine and fully human, with two natures united in one person “without confusion, without change, without division, without separation.” This Chalcedonian Definition solidified orthodox Christology in the Chalcedonian Churches but led to the schism with the non-Chalcedonian (Oriental Orthodox) Churches, including the Coptic, Ethiopian, Armenian, and Syriac Orthodox Churches⁷.

This council was convened to resolve lingering tensions over the Christological disputes from Chalcedon. It reaffirmed the condemnation of Nestorianism and sought to reconcile the non-Chalcedonian Churches by condemning the so-called “Three Chapters”—writings associated with Nestorian theology. While it maintained the Chalcedonian Definition, it did little to heal the rift with the Oriental Orthodox Churches⁸.

The Third Council of Constantinople addressed the heresy of Monothelitism, which claimed that Christ had only one will (divine) rather than two wills (divine and human). The council affirmed that Christ has two wills in accordance with his two natures, preserving the doctrine of the hypostatic union established at Chalcedon⁹. This decision helped clarify orthodox Christology but further distanced dissenting groups¹⁰.

The Second Council of Nicaea was convened to address the iconoclast controversy, a debate over the veneration of icons. Iconoclasts, influenced by the growing power of Islam, opposed the use of religious images, arguing that it constituted idolatry. The council upheld the veneration of icons, distinguishing it from worship (latria), which is due to God alone. This decision restored the use of icons in the Byzantine Church and reaffirmed the importance of sacred art in Christian worship¹¹.

While the first seven ecumenical councils aimed to define orthodoxy and address theological disputes, they also exposed deep cultural and theological divisions within Christendom. Efforts to reunify the Church often faltered due to these underlying tensions.

The filioque clause, meaning “and the Son” in Latin, became one of the most contentious theological and political issues between the Eastern and Western Churches. Its roots can be traced back to debates about the nature of the Holy Trinity. Originally, the Nicene Creed, as formulated at the First Council of Nicaea (AD 325) and later expanded at the First Council of Constantinople (AD 381), stated that the Holy Spirit “proceeds from the Father.” This formulation emphasized the unity of the Trinity and the distinct roles of the Father, Son, and Holy Spirit¹².

In the late 6th century, the Western Church, particularly in Spain, began inserting the phrase filioque into the Creed, stating that the Holy Spirit “proceeds from the Father and the Son.” This was initially intended to combat the heresy of Arianism, which denied the divinity of Christ. By adding filioque, the Western Church sought to affirm Christ's full divinity by emphasizing His role in the procession of the Holy Spirit¹³.

However, this amendment was made unilaterally, without consultation or approval from the Eastern Churches or an ecumenical council. The Eastern Orthodox Church rejected the addition, arguing that it violated the principle established at Nicaea-Constantinople, which prohibited changes to the Creed without universal consensus. The Eastern Church also viewed the addition as a theological error that subordinated the Holy Spirit by undermining the Father's unique role as the sole origin (monarchia) of the Trinity. For the East, the Spirit's procession “from the Father through the Son” was the more accurate understanding¹⁴.

The theological implications were compounded by cultural and political tensions. The filioque controversy became a symbol of the broader rift between the East and West, highlighting differences in how theology was developed and debated. For the Eastern Church, the filioque issue exemplified what they saw as the Western Church's overreach and disregard for collegiality. By the time of the Great Schism in 1054, the filioque controversy had become a central point of division¹⁵.

The question of papal authority was one of the most enduring sources of conflict between the Eastern and Western Churches. From its earliest days, the Church of Rome claimed a special role within Christendom based on the apostolic succession of the Pope as the direct successor of St. Peter. Western theologians pointed to Christ's words in the Gospel of Matthew: “You are Peter, and on this rock, I will build my church” (Matthew 16:18) as the foundation for the Pope's unique authority¹⁶.

By the time of the fall of the Western Roman Empire (AD 476), the Bishop of Rome had emerged as the most prominent leader in the West, both spiritually and politically. Over the centuries, the papacy developed a hierarchical model of governance, asserting that the Pope held universal jurisdiction over all Christians. The Pope was seen not only as “first among equals” (a term often used in the East for the patriarchs) but as having supreme authority over all other bishops¹⁷.

In contrast, the Eastern Orthodox Church adhered to a conciliar model of governance, in which authority was shared among the five patriarchates (Rome, Constantinople, Alexandria, Antioch, and Jerusalem). While the Bishop of Rome was honored as the “first among equals” due to the apostolic significance of the city and its association with Peter and Paul, the Eastern Churches rejected the idea of papal supremacy. Instead, they emphasized the role of ecumenical councils in governing the Church and safeguarding doctrine.

Tensions over papal primacy escalated in the 9th century during the Photian Schism, named after Patriarch Photius of Constantinople, who clashed with Pope Nicholas I over issues of jurisdiction and the filioque. By the time of the Great Schism in 1054, the Eastern Churches viewed Rome's claims to universal jurisdiction as overstepping the traditional boundaries of Church authority, further exacerbating the divide¹⁸.

The split between the Eastern and Western Churches was not merely theological or political; it was also deeply rooted in cultural and linguistic differences that had been developing for centuries.

Language
The Greek-speaking East and the Latin-speaking West experienced increasing difficulties in communication and mutual understanding. Greek, the language of the New Testament and early Church Fathers, continued to dominate in the Eastern Roman (Byzantine) Empire. In contrast, the Latin language came to define the Western Roman Empire and its ecclesial tradition. Over time, these linguistic differences contributed to separate theological vocabularies and interpretations. For instance, key terms like ousia (essence) and hypostasis (person) in Trinitarian theology were nuanced in ways that often led to misunderstandings across linguistic lines¹⁹.

Theological Approach
The East emphasized a mystical and contemplative theology, rooted in the writings of the Greek Fathers such as Gregory of Nyssa, Basil the Great, and John Chrysostom. Theology was viewed as a means of encountering God through prayer and experience, often expressed in rich liturgical practices and symbolism. Conversely, the West developed a more legalistic and systematic approach, particularly under the influence of figures like Augustine of Hippo. The West emphasized precise definitions of doctrine and ecclesiastical governance, as seen in the development of canon law²⁰.

Cultural Contexts
Culturally, the East and West were shaped by different historical trajectories. The Eastern Roman Empire (Byzantium) maintained a strong connection between Church and state, with the Emperor often playing a significant role in ecclesiastical matters. This “Caesaropapism” was foreign to the West, where the fall of the Roman Empire left the Pope as a central authority figure in both spiritual and temporal matters. The divergent experiences of the East and West contributed to their differing visions of how the Church should be governed and its role in society²¹.

These cultural and linguistic differences compounded theological and administrative disputes, creating a growing sense of “otherness” between the two halves of Christendom. By 1054, these divides had become insurmountable, contributing to the mutual excommunications that marked the formal split between the Eastern Orthodox and Roman Catholic Churches²².

The Great Schism of AD 1054 was the culmination of centuries of escalating theological, political, and cultural tensions between the Eastern Orthodox Church and the Roman Catholic Church. Though this event is often portrayed as a single moment of rupture, it was, in reality, the result of a complex and gradual process of estrangement that had been unfolding for centuries. The mutual excommunications in AD 1054, while highly symbolic, marked a formalization of the division rather than its origin.

By the mid-11th century, relations between the East and West were at a breaking point. The Byzantine Empire faced external threats from the Seljuk Turks, and Emperor Constantine IX sought to strengthen ties with the West. However, tensions within the Church undermined these efforts. In 1053, Patriarch Michael Cerularius of Constantinople closed Latin-rite churches in the Byzantine capital and issued a letter denouncing certain Western practices, including the use of unleavened bread and the inclusion of the filioque in the Creed²³.

In response, Pope Leo IX sent a delegation to Constantinople in 1054, led by Cardinal Humbert of Silva Candida, to address the disputes and assert papal authority. The delegation arrived with a letter from Pope Leo IX asserting the primacy of the Roman See. However, their mission was marred by mutual hostility and arrogance. Humbert's confrontational demeanor alienated the Byzantine court and clergy, while Patriarch Michael Cerularius refused to recognize the Pope's claims to universal jurisdiction²⁴.

On July 16, 1054, after months of fruitless negotiations, Cardinal Humbert placed a bull of excommunication on the altar of the Hagia Sophia, denouncing Patriarch Michael Cerularius and his followers. In retaliation, Cerularius convened a synod and issued a counter-excommunication against Humbert and his delegation. These mutual excommunications symbolized the formal break between the Eastern and Western Churches²⁵.

It is important to note that the excommunications were not universally recognized at the time. Many Christians in both East and West continued to view the events as a temporary crisis rather than a permanent division. However, subsequent events, including the Crusades and the sacking of Constantinople during the Fourth Crusade in 1204, deepened the divide and made reconciliation increasingly unlikely²⁶.

The Great Schism solidified the division between the Roman Catholic Church and the Eastern Orthodox Church, creating two distinct branches of Christianity. Over time, the rift expanded as both Churches developed independently:

• The Western Church centralized its governance under the Pope, emphasized scholastic theology, and used Latin as its liturgical language.
• The Eastern Church maintained its conciliar governance model, emphasized mystical theology, and preserved Greek as its primary liturgical language²⁷.

The mutual excommunications remained in place for nearly a millennium. In 1965, as part of broader efforts toward ecumenism, Pope Paul VI and Patriarch Athenagoras I of Constantinople lifted the excommunications in a historic gesture of reconciliation. However, full communion between the two Churches has not yet been restored, and the schism remains a defining event in Christian history²⁸.

The first seven ecumenical councils were pivotal in shaping the theological and administrative structure of Christendom. They sought to unify the Church under a shared orthodox faith but often exposed and deepened divisions. The theological controversies and cultural differences that arose during this period set the stage for the Great Schism of 1054, which permanently divided the Christian world. Despite numerous attempts at reconciliation, the legacy of these councils remains both a testament to the Church's commitment to doctrinal clarity and a reminder of the challenges of maintaining unity in diversity.

1. Davis, Leo D. The First Seven Ecumenical Councils (325–787), pp. 44–46.
2. Pelikan, Jaroslav. The Spirit of Eastern Christendom (600–1700), pp. 58–62.
3. González, Justo L. The Story of Christianity, Vol. 1: The Early Church to the Dawn of the Reformation, pp. 234–239.
4. Meyendorff, John. Byzantine Theology: Historical Trends and Doctrinal Themes, pp. 145–149.
5. Ware, Timothy. The Orthodox Church, pp. 54–57.
6. Chadwick, Henry. East and West: The Making of a Rift in the Church, pp. 155–158.
7. Ostrogorsky, George. History of the Byzantine State, pp. 144–147.
8. Cross, F.L., and Livingstone, E.A. The Oxford Dictionary of the Christian Church, pp. 150–155.
9. Runciman, Steven. The Eastern Schism, pp. 157–160.
10. Erickson, John H. The Challenge of Our Past: Studies in Orthodox Canon Law and Church History, pp. 69–73.
11. Frend, W.H.C. The Rise of Christianity, pp. 121–123.
12. Davis, Leo D. The First Seven Ecumenical Councils (325–787), pp. 276–278.
13. Pelikan, Jaroslav. The Spirit of Eastern Christendom (600–1700), pp. 83–86.
14. Meyendorff, John. Byzantine Theology: Historical Trends and Doctrinal Themes, pp. 185–189.
15. Chadwick, Henry. East and West: The Making of a Rift in the Church, pp. 115–118.
16. Ware, Timothy. The Orthodox Church, pp. 69–72.
17. González, Justo L. The Story of Christianity, Vol. 1: The Early Church to the Dawn of the Reformation, pp. 321–323.
18. Runciman, Steven. The Eastern Schism, pp. 102–105.
19. Cross, F.L., and Livingstone, E.A. The Oxford Dictionary of the Christian Church, pp. 265–267.
20. Erickson, John H. The Challenge of Our Past: Studies in Orthodox Canon Law and Church History, pp. 74–78.
21. Frend, W.H.C. The Rise of Christianity, pp. 124–128.
22. Ostrogorsky, George. History of the Byzantine State, pp. 294–298.
23. Davis, Leo D. The First Seven Ecumenical Councils (325–787), pp. 286–288.
24. Meyendorff, John. Imperial Unity and Christian Divisions: The Church AD 450–680, pp. 320–322.
25. Chadwick, Henry. East and West: The Making of a Rift in the Church, pp. 129–131.
26. Runciman, Steven. The Eastern Schism, pp. 114–116.
27. Ware, Timothy. The Orthodox Church, pp. 73–76.
28. González, Justo L. The Story of Christianity, Vol. 1: The Early Church to the Dawn of the Reformation, pp. 325–328.