This chapter suggests that the papacy dealt with Protestantism in various ways. It condemned the forty-one propositions of Martin Luther and then waited for the Council of Trent to condemn others. It used the institutions of preventive press censorship and of various inquisitions to check heresy. It sought the support of Christian rulers to prevent its spread, sending nuncios and legates to the rulers of the Holy Roman Empire, France, England, Scotland, Sweden, Denmark, and Poland–Lithuania to urge them to suppress heresy and to secure their loyalty by negotiating agreements on Church appointments and shared revenues and by offering military aid, efforts that had mixed success, or failed. Religious orders such as the Jesuits and Capuchins were also enlisted in the struggle. Leading Protestant reformers came to see the papacy as the Antichrist or foreign usurper.

This chapter examines two so-called transitional theologians who straddled the worlds of orthodox belief and learning and forward-looking scholarship and literary engagement. Johann Lorenz von Mosheim (1693–1755) and Johann Georg Walch (1693–1775) pointed the way to a new view of the Reformation, even if the results of their interventions went much farther then they intended. Mosheim’s History of Michael Servetus sought a type of transhistorical reconciliation between the eponymous Spanish heretic and John Calvin, who had him burned at the stake in Geneva. Mosheim tried to acknowledge the occasional brutality of Reformation-era Protestants while contextualizing the historical attitudes of an earlier era. Walch’s twenty-four-volume Luther edition was notable not only for rendering Luther’s language into a readable vernacular, but also for a long historical essay on Luther’s “accomplishments.” Walch sought to both acknowledge the genuine contributions of the first Reformer while also stripping away some of the mythical status that had accrued to Luther through generations of pious veneration.

The final chapter provides an examination of how the Merovingian world was shaped by opposition to paganism, heresy, Judaism, and, at the end, the new Islamic world of the Arab caliphate. The Franks (or at least some of them) had started as pagans themselves in the fifth century, and stories of conversion created important reminders of the journeys to salvation. Whether ‘real paganism’ is easily identifiable in stories or grave goods we may doubt. Similarly, the presence of heresy or Judaism can seem ambiguous when the sources are interrogated. But the creation of Frankish Christianity relied on its contrasts and those fed to it by the Byzantine Empire. Through Merovingian accounts of religious conflict we can discern how the Frankish kingdoms saw their place in the wider world.

The book is devoted to the relationships between Nicene and Homoian Christianities in the context of broader religious and social changes in post-Roman societies from the end of the fourth to the seventh century. The main analytical and interpretative tools used in this study are religious conversion and ecclesiastical competition. It examines sources discussing Nicene–Homoian encounters in Vandal Africa, Gothic and Lombard Italy, Gaul, and Hispania – regions where the polities of the Goths, Suevi, Burgundians, and Franks emerged. It explores the extent to which these encounters were shaped by various religious policies and political decisions rooted in narratives of conversion and confessional rivalry. Through this analysis, the aim is to offer a nuanced interpretation of how Christians in the successor kingdoms handled religious dissent and how these actions manifested in social practices.

The Introduction presents the main topic of the book – the role of conversion and competition between Nicene and Homoian churches in the post-Roman West – and the methods applied. It explains terminology (Nicene, Homoian), theorises the concept of conversion as a tool of historical analysis, and presents the purpose of the cross-regional comparison that follows.

The fourth century AD historian Ammianus Marcellinus remarked that “no wild beasts are such enemies to mankind as are most of the Christians in their deadly hatred of one another.” More to the point, the discussion of the nature of Christ drove a wedge within Christian communities in Antioch as elsewhere and ignited conflicts on a unprecedented scale. This chapter describes how the playing out of these debates had repercussions at all the levels of Antiochene society.

This chapter traces the fortunes of our modern understanding of ‘belief’ which is deeply informed by its original uses in a religious context. It begins with an account of faith/belief (Greek: pistis) in early Christianity, showing how the primary meanings of the term related to trust rather than intellectual assent. In the medieval period, this social component of faith/belief was formalised in the conception of ‘implicit faith’, which enabled lay believers to affirm abstruse theological doctrines without the requirement of a full intellectual comprehension of what was being affirmed. While it is possible to speak of the propositional content of belief during this period, the identity of the faithful was established more by liturgical practice than assent to doctrinal propositions.

The conclusion proposes alternative ways to think about Christian normativity, drawing on the concepts of polydoxy and religious autonomy from Alvin Reines, with additional support from Catherine Keller and Laurel Schneider, and the concept of theological disobedience, derived from Louis Michael Seidman’s notion of constitutional disobedience.

Oral witness is also the basis for the account of what Margery Baxter, charged with heresy at Norwich in 1428, has said and done. Her friends and neighbours are called to witness against her, and through their words we learn not only of the shocking things she has said which confirm her contempt for the Church, but details of the women’s lives.

The last fifty years have seen a considerable boom in the study of ancient book culture, reading and scribal habits. This chapter situates the present study in light of these scholarly developments and raises some critical questions concerning certain viewpoints that have been put forward regarding how to approach the Nag Hammadi codices given what is known about religious materiality in antiquity. In light of the latest scholarship on ancient literacy surveyed in this chapter, it is argued that the texts were most likely produced by and for the direct use of a small educated societal minority. The chapter also addresses some of the old and new scholarly paradigms and ideological setups in the scholarship on the texts: for example, the potential and limits of the trend called ‘New Philology’, as well as the problems attached to concepts like ‘heresy’ and ‘Gnosticism’ and their persistent connection with the Nag Hammadi collection.

Although entry into Islam is costless, exit was banned early on. According to a widely accepted interpretation of early Islam, soon after Muhammad’s death a precedent for banning apostasy was set. In fact, the underlying dispute was over zakat, and the episode amounted to enforcing the tax code. But recasting this historical detail would not necessarily settle controversies over Muslim religious freedoms. Certain Quran verses speak of retribution against nonbelievers. Others preclude compulsion, arguably establishing a right to leave Islam. Insofar as a textual inconsistency exists – and that itself is debatable – for advocates of liberalizing Islam the challenge boils down to prioritizing liberal verses. Blasphemy and heresy charges, used repeatedly to persecute heterodox sects, also restrict sundry liberties. The fear of getting accused of religious offense constrains political discourse and inhibits collective action. But a broadening of Muslim religious freedoms through the liberalization of apostasy and blasphemy rules is not unthinkable. Analogous transformations have occurred in other religions. Besides, Islam has been reinterpreted repeatedly since its emergence, radically so in modern times. Innovations include Islamic banks, which are business corporations, and various Islamic NGOs, which are organized as nonprofit corporations. Evidently, no absolute barrier exists to broadening Islamic religious freedoms.

The first section addresses the debate between Julian’s supporters and detractors following his sudden death in 363. Christian preachers turned Julian’s propagandistic use of his life into proof that Roman history was regulated by Christian providence. However, they also had to confront Julian’s re-assessment of the power dynamics between the ruler and the priests in the post-Constantinian empire. I argue that Julian was wary of how the identification of religious allegiance as the criterion for determining whether an emperor was a philosopher-ruler affected the interaction between the emperor, now decentred from his religious structures of choice, and the ecclesiastical leaders. The second section shows that that the episcopal engagement with philosophical ideas both provided clerics with a weapon against Julian’s attempts to re-centre the ruler in religious matters and shaped the relationship between the bishops and emperors in addressing heresy - a key challenge faced by Christianity in its self-construction as perfect system of knowledge. Episcopal appeals to an exclusive control of knowledge also affected the public role of non-conforming philosophers, which I illustrate with a case study of Synesius of Cyrene.

In 1208 Pope Innocent III proclaimed a crusade of “extermination” and “expurgation” against the heretics supposedly infesting the lands of the count of Toulouse. What is now known as the “Albigensian Crusade” lasted twenty-one years and was the first holy war in which Christians were guaranteed salvation by killing other Christians. The massacres during the crusade, especially at Béziers in 1209, were “genocidal moments.” The victims, though, were neither an ethnic, national, or racial group. The victims were arguably a regional or possibly a cultural group, but such groups are not covered by the modern legal definition of genocide. Nevertheless, they were deliberately targeted for destruction. Despite accusations of heresy, the victims were not initially a self-consciously different religious group either. Crucially, they were not “Cathars,” which is what most medieval historians and genocide scholars assume the victims to have been. “Catharism” as a medieval heresy never existed; it was an invention of nineteenth-century scholars trying to understand the Albigensian crusade more “scientifically” and less confessionally. Finally, were the individual testimonies collected by the first inquisitions into heretical depravity, established in Toulouse in the aftermath of the Albigensian crusade, analogous to the memories of individuals who witnessed or survived genocides collected by modern tribunals?

This chapter proposes a new framework for the study of the categories of heresy and orthodoxy in medieval Islam. It engages with scholarship on these categories in the discipline of Islamic Studies and Religious Studies more broadly, arguing that orthodoxy and heresy should not be viewed solely through the prism of theology, which emphasises belief (doxa) and practice (praxis). Instead, it highlights the discursive formation of conceptions of orthodoxy and heresy. Heresy and orthodoxy are defined as shifting categories of denunciation and approval, which provides insights into the formation of orthodoxy as a contested process. This approach allows for a more detailed and complex typology of proto-Sunni movements in the eighth to eleventh centuries, admitting more variation than previous scholarship has allowed for.

This chapter provides a comprehensive examination of how hostility towards Abu Hanifa evolved over three centuries among the proto-Sunni traditionalist network. It argues that the construction of heresy and orthodoxy depended on the circulation of discourses of heresy among textual communities. Transregional proto-Sunni traditionalists developed informal ways to regulate, discipline, and shape conceptions of orthodoxy and heresy. The chapter brings into sharp focus the key agents of proto-Sunni traditionalist orthodoxy: its texts, scholars, and figures who articulated and promulgated discourses of heresy. We can now discern a mature and virulent discourse of heresy among an influential network of proto-Sunni traditionalists seeking to malign, exclude, and marginalise Abu Hanifa and his followers from the proto-Sunni traditionalist conception of orthodoxy. In the tenth century, however, we can observe some attempts by proto-Sunni traditionalists to depart from the network’s emerging consensus and adopt a more accommodating tone towards Abu Hanifa and his followers, which marks the beginning of a broader conception of Sunni orthodoxy.