With the widespread acceptance in the West of tolerance as a moral and political virtue comes the temptation to read its modern connotations into the past, a form of historicism that M.-Y. Perrin warns against in his foreword and Peter Van Nuffelen strives to counter throughout Penser la tolérance. This book presents itself as an exercise in intellectual and cultural history that is aimed at helping readers bridge the hermeneutical gap between past and present understandings of tolerance by means of curated tours of its historiographical and historical underpinnings. As a work that originated in conferences at the École Pratique des Hautes Études's Section Sciences des religieuses in 2013, it takes as its point of departure the origins of the concept in Greek philosophy and examines how rising Christian monotheism and a centralising Roman state contributed to its transformation in late antiquity.

Van Nuffelen organises his book as an archaeology of knowledge that follows key moments that (re)shaped the conception of tolerance. Chapter i problematises our understanding of the idea through a comparison of ancient and modern approaches that have not only markedly different starting points but also greatly dissimilar valences. Remaining chapters examine the main dossier of the book, namely how specific historical figures and scenarios illustrate just how the idea of tolerance was appropriated and transformed between about 300 and about 600 when interactions within the context of an established Christianity and the late Roman state transformed attitudes as well as practice in regard to people's reception of difference. Chapter ii discusses the relationship between persuasion by words and other forms of competition, including the trials of power or ordeals, reprising more detailed studies that the author has published elsewhere. Even as multiple ways to offer proof or demonstration were available to late antique persons, rational persuasion retained its appeal, given how the logos was central to the quest for the truth within variegated ancient intellectual traditions. Chapter iii explores the implications of Christianisation as Christian leaders sought not only to oppose pagan cult in the form of public sacrifice and temples cult but to effect a more thorough-going transformation of converts' habits and customs. As proponent of the paternalistic principle of benevolent coercion, Augustine of Hippo argues that just as a child needs a grammarian's disciplina to learn, Christians require firm guidance from Church and State to help them to recast their customs and habits in a more Christian form. Chapter iv treats the reception of religious violence, which many Christians construed as pious acts aimed at achieving the noble goals of correcting error and saving souls. It focuses on the destruction of the Serapeum in Alexandria-by-Egypt, the most well-known case of the Christian repression of traditional temple cult, and Severus of Minorca's forcible conversion of local Jews and the destruction of their synagogue, interventions that Christians at the time hailed as acts of sacred violence. The epilogue restates the importance of recognising ancient approaches to (in)tolerance as being rooted in their own fields of meaning and that they are, moreover, much more nuanced when compared to our own simpler and simplistic views today.

The author makes a clear argument whose main point is that tolerance was never considered an abstract virtue, let alone its own telos, in antiquity, whereas such an idea meets with general acceptance in today's world. As a secondary expression rather than a good in itself, tolerance was one of the means to achieve the end of promoting the welfare of a group. Thus the good of a group, be it the city, the imperial state or the Christian community, constituted the measure by which specific stances or acts ranging from toleration to active coercion would be judged and ascribed value. Just as some philosophers presented their own pluralistic and competitive claims as ultimately beneficial to man's quest for knowledge, so writers such as Themistius and Symmachus pleaded for the co-existence of Christians and pagans by adapting this philosophical trope to stress the manifold ways by which one can arrive at the ultimate truth, an aspect of the monarchical monotheism or henotheism that was the hallmark of the late ancient philosophical tradition. On the other hand, Christians showed themselves willing to use logocentric rational argumentation to present their beliefs and persuade others in certain instances and just as ready to resort to the application of force including committing acts of violence to promote their cause in others. Although a modern reader may regard these two sets of options as polar opposites, late antique Christians experienced no such dissonance as they prioritised securing the good of the group as the foremost consideration and assessed the value of actions and attitudes accordingly.

Penser la tolérance is as much an introduction to the ancient concept of tolerance as a protreptic guide to the historical method. It gently coaches its reader to reflect on this key idea that is today greeted with banal acceptance by recognising the value of appreciating the idea's subtler inflections and diverse historical sources in the more distant past. The book's persuasive argument and elegant presentation of its historical dossier helpfully illuminates how tolerance operated within a majority Christian society, just as notable modern classics on the topic, such as the writings of Thomas Hobbes and John Locke, are similarly concerned with the relationship between an established Church and other Christian denominations within a Christian nation. As Van Nuffelen reiterates in his epilogue, the necessity of selective treatment has entailed the deliberate omission of material that may otherwise merit inclusion, including how Christians living under Sassanian and later Muslim rule adapted the idea of tolerance to fit their own circumstances. While it may be churlish to suggest further examples given the choice basket of material that the author has already presented, more treatment of Jews and Judaism, atheists and atheism, and how an invented secular sphere, the saeculum, set conceptual and pragmatic limits on Christianisation, as well as consideration of how local communities received or even resisted religious hegemony, may further enrich our appreciation of the operations of tolerance as idea and practice both in antiquity and in our own time.