Among the many issues that divide East and West, the papacy is arguably the largest issue that concerns theologians today. This sentiment has been repeated by many Christian leaders, Catholics and Orthodox alike. Take for example the words of Pope Paul VI who stated in 1967 that addressing how to understand the papacy is “undoubtedly the gravest obstacle to the path of ecumenism.”
This sentiment has been echoed by many in both the Eastern Orthodox and the Roman Catholic Churches, including George Malony, Olivier Clément, John Zizoulas, and John Meyendorff. Similarly, Walter Cardinal Kasper, head of the Pontifical Council for Promoting Christian Unity in Rome, has even gone so far as to claim that, “the only seriously debated theological issue between us and the Orthodox Church… is the question of Roman primacy.”
A Brief overview of History
Up until the eleventh century, the Eastern and the Western churches related to one another primarily through a kind of Eucharistic ecclesiology that was exhibited in an affiliation of episcopal synodality. Churches functioned, in general, along a principle of ecclesial subsidiarity. Local communities of Christians were united under a Bishop, forming a local church. They understood their unity with other Christians as rooted in the shared Eucharist and profession of faith. When challenges arose there developed a system of synods where the relevant bishops could gather and make decisions about how to resolve conflict in the Church. These councils were varied in their scope. The councils that bore on the whole life of the Church are what became known as ecumenical councils. There also developed further localized synods. These were presided over by a regional bishop who was known, particularly in the East, as the patriarch.
The patriarchs developed organically in different areas as a result of a combination of factors including the political influence of their see, the apostolic relationship of their chair, the liturgical influence of their rites and the historical significance of their communities. Within this system the Bishop of Rome held a place of great honor. Many of the fathers wrote of Rome’s central role in the Church, and spoke of Rome’s bishop as preeminent among the college of bishops. Following the Council of Sardica, Rome was seen as a center of appeal for other bishops within the Church as disputes emerged. However the Council of Sardica itself is not considered to be an ecumenical council by Eastern Christians.
After the sacking of Rome, the pope became increasingly influential in the west, while the patriarchs of the east developed their own organizational structures. They maintained synodical and Eucharistic unity but were increasingly detached from one another in their administration. Following the mutual excommunications of 1054 between East and West, the Eucharistic unity of the Churches was enduringly damaged. Efforts at reconciliation were not successful and in the intervening centuries the wounds of disunity were deepened.
Both eastern and western churches continued to develop their theological understanding about their respective patriarchs, which created additional tension. In 1848 Pope Pius IX wrote an encyclical “To the Easterns” which offered a set of terms for reunification to the east. Synods in Constantinople, Jerusalem, and Antioch responded with their own “Encyclical of the Eastern Patriarchs.” The response lays out their primary issues, among which were chiefly the filioque in the Creed and the Eastern Catholic Churches in their lands. These concerns would soon be compounded when the Catholic understanding of the Pope’s role as a universal teacher for the Church was finally defined on July 18, 1870 when Vatican I professed a doctrine of papal infallibility. This statement marked a decisive turn in Catholic Orthodox dialog. After Vatican I, the issue of the papacy increasingly became understood as the primary issue dividing east and west.
In the Twentieth Century there was an increase in fervor over ecumenical dialog. As the threat of communism loomed over many Orthodox Christians, the Eastern Orthodox Church began discussions with the World Council of Churches, and officially joined in in 1961. When Vatican II was called, the Eastern Orthodox were invited to attend as observers. They however declined, citing the statements on papal infallibility from Vatican I as the principle hurdle. The council itself marked a decisive turn toward ecumenism which can be seen most clearly in the decree Unitatis Redintegratio. This increase in Orthodox-Catholic dialog has been born out in the establishment of “The Joint International Commission for Theological Dialogue Between the Catholic Church and the Orthodox Church” (JIC). This commission has held twelve plenary sessions, which have recently addressed the issue of the papacy directly.
In recent years there has been an increase in papal concern about unity between east and west. This can be seen most clearly in the documents Ut Unum Sint, and Orientale Lumen. Additionally Pope John Paul II issued an apology in 2001 to Archbishop Christodoulos of Greece for the Crusades in response to a list of thirteen offenses against Eastern Orthodox Christians, including the Fourth Crusade. There have also been increased meetings between the Pope and the Patriarch of Constantinople.
Since the fall of the U.S.S.R. ecumenical dialog has faced a variety of its own challenges. The collapse of communism made way for a revival of the Eastern Catholic Churches in many of the Eastern Bloc states. These “uniates” exasperated old tensions. The voices against ecumenism also grew stronger. The necessity for global support had diminished along with the threats from soviet authority. Now the Orthodox had less reason to support unity. Ecumenism gave way to confessionalism. This was compounded by the magisterial establishment of Catholic structures in Russia as the Pope set up “apostolic administrations” in the region, creating fears of Roman Catholic imperialism. This suspicion created a stalemate on ecumenical dialog in the 1990s and JIC sessions were suspended for more than 6 years. The papacies of Benedict XVI and Francis have encouraged greater dialog, which has once again begun in earnest, the fruits of which hitherto remain unseen.
 Pope Paul VI, “Address to the Secretariat for Promoting Christian Unity,” in Doing the Truth in Charity: Statements of Popes Paul VI, John Paul I, John Paul II and the Secretariat for Promoting Christian Unity, ed. Thomas F. Stransky and John B. Sheerin (New York: Paulist Press, 1981), 271–75.
 For a survey of thought on the importance of addressing primacy see: Adam A. J. DeVille, Orthodoxy and the Roman Papacy: Ut Unum Sint and the Prospects of East-West Unity (Notre Dame, IN: University of Notre Dame Press, 2011), 1–8.
Walter Kasper, “That They May All Be One: The Call to Unity Today” (London: Burns and Oates, 2004), 19. as quoted in DeVille, Orthodoxy and the Roman Papacy: Ut Unum Sint and the Prospects of East-West Unity, 9.
For a full exposition on this Eucharistic communion see: Nicholas Afanasiev, “The Church Which Presides in Love,” in The Primacy of Peter, ed. John Meyendorff (Crestwood, NY: St Vladimir’s Seminary Press, 1992), 91–143.
DeVille, Orthodoxy and the Roman Papacy: Ut Unum Sint and the Prospects of East-West Unity, 78–81.
Vsevold of Scopelos, “What About the Roman Primacy?,” in We Are All Brothers: A Collection of the Writings of Bishop Vsevolod of Scopelos (Fairfax, VA: Eastern Christian Publications, 1999), 263.
 There were some Churches that had already broken this unity, i.e the Oriental Orthodox Churches, and the Great Church of the East, a full examination of which is beyond the scope of this brief overview. For an in depth study on this see: Wilhelm Baum and Dietmar W. Winkler, The Church of the East: A Concise History (New York: Routledge, 2010). and Lois M. Farag, The Coptic Christian Heritage: History, Faith and Culture, 1 edition (New York: Routledge, 2013).
 Robert Taft has recently argued that in spite of the anathemas of 1054, the sack of Constantinople in 1204, and the formal repudiation of the union of Florence in 1484, eastern and western Christians often behaved as if no breach in communion had occurred. See: Robert Taft, “Perceptions and Realities in Orthodox-Catholic Relations Today: Reflections on the Past, Prospects for the Future,” in Orthodox Constructions of the West (Fordham University Press, 2013), 23–44.
See discussion in: Thomas Hopko, “Roman Presidency and Christian Unity in Our Time” (Woodstock Forum, 2005), 4.
 Maximus Vgenpoulos, Primacy in the Church from Vatican I to Vatican II: An Orthodox Perspective (DeKalb, IL: NIU Press, 2013), 25–8.
Most of the Orthodox churches outside the communist world (Greece, Constantinople) were members from 1948. 1961 saw the entrance of the Russians and many of the other Orthodox churches in communist countries Kaisamari Hintikka, “The Pride and Prejudice of Romaian Orthodox Ecumenism,” in Orthodox Christianity and Contemporary Europe, ed. Jonathan Sutton and William Peter van der Bercken (Leuven: Peeters, 2003), 456–7.
 Moscow and Constaninople did send observers to some of the later sessions of the Council. Maximus Vgenpoulos, Primacy in the Church from Vatican I to Vatican II: An Orthodox Perspective, 97.
 The meetings in 2009 and 2010 were on the topic of “The Role of the Bishop of Rome in the Communion of the Church in the First Millennium.” The Russians were not present because of the canonical argument over Estonia and have been critical of the Ravenna text that was adopted.
 George E. Demacopoulos and Aristotle Papanikolaou, “Orthodox Naming of the Other: A Postcolonial Approach,” in Orthodox Constructions of the West, ed. George E. Demacopoulos and Aristotle Papanikolaou (New York: Fordham University Press, 2014), 5–6.
 DeVille, Orthodoxy and the Roman Papacy: Ut Unum Sint and the Prospects of East-West Unity, 14–15.
 Ibid., 15.