In our religiously and politically polarized landscape, it is worth recalling that the quest for Christian unity is as old as the faith itself. Unsurprisingly, Christian unity has remained a major theme for articles in the journal Church History since its founding in 1932, even to the extent that one of the American Society of Church History’s annual prizes came to be focused on issues of unity and disunity in light of the diversity of global Christianity. The quest to bring fractured Christian movements closer together has taken many forms, ranging from the “top down” of ecumenical councils, church confessions, formal dialogues, and efforts at denominational mergers, to the “bottom up” of grassroots social movements, utopian experiments, missional collaborations, and transcultural spiritual networking. It involves both internal theological formulations that anchor ecclesial identities and external outreach for public purposes such as nation building, ethnic solidarity, or resistance to oppression. Selecting a dozen articles on the subject of Christian unity has therefore required narrowing the scope to one particular angle, namely, to the quest itself. Rather than focusing on the internal theological dimensions of Christian unity, we have selected a range of articles on the striving for unity, better understanding across difference, and the recognition of commonalities between diverse and divided communities. These articles also explore the implications of this aspiration for the public and social dimensions of the faith. The quest for Christian unity is a multi-ecclesial and enduring theme with unexpected implications for the meaning of Christianity in various times and places.

The 1700th anniversary of the Council of Nicaea (325 CE) provides an opportune moment for the readers of Church History to look back through history at the myriad ways in which the quest for Christian unity presented itself. Beginning with Nicaea, the first of the so-called “ecumenical” or “universal” councils, which claimed to represent the entire Christian world, we move on to councils where the scope of their authority was contested, and thence to the modern era, where issues of authority are matters for negotiation and conversation between independent entities.

The articles introduced here and republished in this virtual issue reflect an extraordinary diversity both of approaches and outcomes. Even with the best of intentions, it was often not possible to achieve real meetings of minds, especially between conflicted theological worlds such as those of Eastern and Western Christianity. If one believed that some sacred and eternal truth was at stake, recognizing the worth of the other person’s viewpoint required either exemplary humility or the conviction that truth somehow transcended the available attempts to express it.

The first two articles cover the age of the great councils of the church. While Emperor Constantine is well known for calling the first ecumenical council at Nicaea, in “Constantine and Consensus,” H.A. Drake focuses on his motivations and general approach to religious unity, which he describes as the emperor’s “foremost goal.”Footnote ¹ He emphasizes Constantine’s preference for pragmatists over ideologues, for those who chose peace and unity over doctrinal rigor and theological precision. While scholars often describe Constantine’s reign as a “revolution,” Drake suggests that his consistent pursuit of unity or “consensus” – a peaceful coexistence that included diverse Christians and even many non-Christians – more accurately represents his contribution.

Even before the era of the ecumenical councils, theologians might appeal to a common ancient tradition of the faith as a source of unity. Robert Wilken demonstrates the limitations of this approach in his article “Tradition, Exegesis, and the Christological Controversies.”Footnote ² In their conflicting interpretations of certain New Testament passages, Bishops Cyril of Alexandria and Nestorius of Constantinople both appealed to an important strand of a particular rather than a universal tradition, each of which had older exegetical and theological support. Unfortunately, neither could recognize the other’s interpretation as part of a broader tradition nor affirm a meaningful Christian unity within diversity.

The next two articles address the continuing role of church councils in the late medieval and early modern quest for unity. In his classic article on the Council of Florence (1438–1439), Deno Geanakoplos turns to the problem of union between the increasingly estranged Christian worlds of the Byzantine East and Latin West.Footnote ³ Despite strong motivations for union, a primary effort of both popes and emperors for centuries, he analyzes the complex factors that bedeviled these efforts at Florence. Alongside the politico-ecclesiastical tensions and the mutual mistrust between the Greeks and Latins, the negotiations had actually become three-sided, with the conciliarists alongside the papacy vying for the favor of the Byzantines. Francis Oakley, the great historian of conciliarism, tackled a seemingly impossible task in identifying the residue of conciliar theory at the fiercely papalist Fifth Lateran Council of 1512–1517.Footnote ⁴ Yet he demonstrated that one key plank of the councils’ platform, the reform of the Church, was alive, at least as an aspiration. Even the most ambitious of the decrees of the Council of Constance, Haec Sancta, with its claim of the superiority of councils over popes, was never utterly repudiated.

Scarcely less easy, at first blush, was John T. McNeill’s effort to portray the ever-theologically precise John Calvin as an “ecumenical churchman.”Footnote ⁵ Yet, McNeill shows, with enormous learning in Calvin’s own writings, that his high concept of the Church absolutely excluded the narrow belief that only one strand of the Reformation was correct. Schism from a church over trifling matters of polity or ceremonial was sinful; every church was imperfect, on a journey to its goal. In another classic article, Winthrop S. Hudson uses the term “denominationalism” in a more positive way than McNeill did in his portrait of Calvin.Footnote ⁶ Somewhat anticipating McNeill’s argument, Hudson shows how the reformers always allowed for diversity between churches, so long as the essential “marks” of the true church were present. His heroes, however, are the Independents of mid-seventeenth-century England, who believed that a plurality of congregationally led churches could provide for spiritual diversity among human beings.

The theme of “aversion to sectarianism” also surfaces in Elizabeth Bouldin’s article on fruitful interactions between different dissenting groups in the late seventeenth and early eighteenth centuries.Footnote ⁷ Those of a Pietistic, spiritualist, or millenarian cast of mind regarded affinity and resemblance in response to the divine as a better basis for friendship and fellow-feeling than creedal or ecclesiological uniformity. The fluidity and ready interaction between different groups possible in colonial North America only increased the opportunities for such encounters.

The search for Christian unity continued in succeeding centuries through efforts at cross-confessional or interdenominational cooperation in diverse national contexts and with differing objectives. In his article, “That All May be One? Church Unity and the German National Idea, 1866–1883,” Stan Landry explores a distinctive aspect of the search for unity across institutional boundaries.Footnote ⁸ Here, the participants are German Catholics and Protestants, seeking dialogue in an ecumenical group amidst the hegemonic, sometimes militaristic Protestantism of the Kulturkampf. Landry argues that the Ut Omnes Unum movement aspired to create a united German identity that transcended confessional boundaries.

In the United States, the Federal Council of Churches (FCC) was the most important organization for interdenominational cooperation between 1908 and 1950, when it merged into the new National Council of Churches. Methodist historian John Abernathy Smith analyzes how, animated by the social gospel, denominational federations collaborated to give birth to the FCC, which represented the vast majority of US Protestants during the first half of the twentieth century.Footnote ⁹ In her study of the Fraternal Council of Negro Churches, noted scholar of the People’s Temple, Mary R. Sawyer, introduces the subject of church unity for racial solidarity.Footnote ¹⁰ She calls the Fraternal Council the “first self-consciously ecumenical body of national scope to be organized by black Americans.” Over its 30 years, the Council supported the human and civil rights of African Americans. One of its last acts was to support the historic 1963 March on Washington.

Focusing on Canada in the twentieth century, John Stackhouse Jr. explores how Canadian evangelical networks facilitated cooperation from the bottom up, even as they situated themselves in contrast to church unity movements among mainline denominations.Footnote ¹¹ Canadian evangelicals demonstrated a “different kind of ecumenism” through practical fellowship rather than formal church mergers, in a manner not dissimilar to the movements described by Elizabeth Bouldin.

The final article in this virtual issue returns to the political dimensions of the quest for Christian unity – not with the goal of consensus or peaceful coexistence, Constantine’s aim in the fourth century, but as a force of resistance to oppression. In “The Politics of Ecumenism in Uganda, 1962–1986,” J.J. Carney, Africanist and scholar of Roman Catholicism, shows how Anglican and Roman Catholic leaders embraced ecumenical solidarity to resist the policies of Ugandan dictator Idi Amin.Footnote ¹² What Carney calls “prophetic protest” characterized the churches’ united stance during the civil war of the 1980s and following.

Works of scholarship associated with significant anniversaries sometimes involve calling up, or even exaggerating, the importance of the event or movement that is commemorated. In this virtual issue, the editors have no such ambition. Rather, we have tried to illustrate how, across at least 1700 years, religious difference and diversity across Christianity evoked a range of constructive responses. Often, those responses have tried to find a means to ensure coexistence, to express community of purpose, to bring diverse and potentially antagonistic church communities into closer and more collegial relationships. Inevitably, some of these efforts failed (at least in the terms envisaged by their most hopeful proponents), yet the quest for unity continued. Sometimes the first step was to acknowledge that, even against a background of political and ceremonial difference, there were grounds for sharing and recognizing each other as partners. Complete visible and structural unity might not always be possible or even thinkable, but finding some measure of common ground certainly could be an aspiration. Such an aspiration could be traced back to the attempts to heal the divisions or at least soothe the differences that have vexed Christians from the fourth century onward.