This excellent collection of essays, based on conferences held at the University of Oxford in 2009 and 2010, stages two critical interventions in the study of late antique conversion. First, as Arietta Papaconstantinou explains in her lengthy introduction, the collection attempts to dislodge the ‘enduring centrality of the Christian paradigm’ (p. xvii) in discussions of conversion, evident in the lingering yet tenacious influence of A. D. Nock's 1933 book on ancient conversion (notably and importantly little cited in the volume under review). These essays expand the traditional terrain of late antique conversion by including not only essays on Christian, Judaism and Islam, but also an essay on Hellenistic polytheism (Polymnia Athanassiadi), an essay on Manichaeism (Samuel Lieu), two essays on Buddhism in East Asia (Antonello Palumbo and Max Deeg), and one essay on post-Soviet Mongolia (Vesna Wallace). (The Wallace essay, while full of interesting information and analysis, remains something of an outlier and does not, in the end, expand our understanding of late antiquity.) The essays have varying degrees of success in engaging with the somewhat stale analytic category of ‘conversion’: some essays, like Deeg's on East Asian Buddhism and Elizabeth Key Fowden's on ‘Rural converters among the Arabs’, evoke the problems and possibilities in critiquing the very notion of transhistorical conversion; others, like Uriel Simonsohn's essay on Jewish, Christian and Islamic conversion regulations in the early Islamic period and Moshe Lavee's essay on the rabbinic conversion of conversion itself, produce fine analyses of their particular subjects but leave conversion as an analytic category more or less intact.

The second, related intervention of the collection comes in questioning the relationship between representations of conversion in our texts and the reality of religious change ‘on the ground’. Since ‘it is inarguably mainly narrative literature which delivers information about conversion’ (Deeg, p. 268) we are too beholden to their over-determined frameworks of clear religious boundaries. This is especially true of hagiography, which appears in many of these essays. ‘Traditional definitions of conversion’, Papaconstantinou writes, ‘are largely inadequate because they take the discursive break for a real one’ (p. xxii). Many of the essays in the collection (with some notable exceptions, such as Konstantin Klein's rather positivist analysis of the conversion of Arabs in Elusa in Jerome's Vita Hilarionis) work at this intersection of critical literary analysis and heuristic revision: how can we reimagine the representational work of our late antique sources in such a way as to expand or reimagine what we mean by ‘conversion’? Many of the contributions end up positing an inverse relationship between the rigid, boundary-fixing rhetoric of our sources and the more fluid, flexible set of encounters and ‘convergences’ (to use Key Fowden's preferred term) ‘on the ground’. The late Thomas Sizgorich's essay offers a particularly sophisticated reading of the contrasting attitudes toward social overlap and closeness rhetorically framed in Christian and Islamic hagiography. (Sizgorich died before the publication of this volume; Papaconstantinou opens the book with an elegant note about him and his exceptional work.)

A compelling opening essay by Averil Cameron, which will henceforth be the de rigueur starting point for any discussion of late antique conversion, articulates some additional themes that run through many of the essays. What is ‘late antiquity’, both as a chronological period but also as a marker of certain cultural concerns? (pp. 4–7) (Athanassiadi's essay takes up this question with gusto, positing that ‘the conversion ethos’ in fact defines ‘the millennium of Hellenistic and later antiquity’ [p. 24]). What are our methodological foundations, and ‘what are the elements that can be compared in relation to conversion?’ (p. 19) (Deeg's essay ably confronts this challenge). How firmly can we even recognise the purported religious groups – Christians, Muslims, Jews and (to use a term that has re-entered our scholarly vocabulary of late) pagans? (pp. 8–9) (Here Christopher Kelly's essay on Augustine and ‘pagan’ conversion offers a salutary warning about the dangers of unquestionably assuming the logic of our sources.) What role does imperial ‘conversion’ and regulation play in the creation of religious boundaries in society? (This question occupies Palumbo as well as Simon Corcoran's survey of Roman imperial legislation from Decius to Justinian.) What do we mean when we talk about ‘Christianisation’ or ‘Islamicisation’ as forms of social, spatial or cultural conversion (p. 7)? (The final two essays on the not-quite conversions of Jerusalem, by Jan Willem Drijvers and Robert Schick, take up this question in detailed surveys of one city's agglomerations and transformations.)

The rich array of sources and approaches in these essays defies simple summary in a review. Some offerings attempt more comparative analyses, while others (such as Lieu's sweeping overview of the spread of Manichaeism) remain in their specialist niches. Method more than subject matter unites the majority of these essays: the belief that the hardening rhetoric of late antique religious boundaries can, despite itself, reveal lands of enormous congruity, overlap and ambiguity.

Hovering over this historiographically optimistic revisioning of the rhetorics and realities of encounter and conversion in late antiquity are the grim present-day conditions of the Middle Eastern context from which most of these sources derive. Papaconstantinou opens her introduction with salacious western headlines from 2014 that claimed to report the so-called Islamic State's threat to ‘convert or die’. Key, Fowden, Lieu and Cameron explicitly invoke the modern conflicts that cannot help but colour our appeal to fluidity and coexistence drawn from our late antique accounts. Cameron closes her essay with an important exhortation: ‘History is not neutral, neither is it innocent. It also imposes an even greater responsibility on those of us who are tackling this difficult subject’ (p. 21). Works such as these on conversion and coexistence have far from merely antiquarian significance. As we labour on the boundaries, crossings and encounters of a world long gone, the ethics of our historical task should not be far from our minds.