It is rare that a single volume is able to capture the many nuances of the writings of late medieval theologians, and at the same time be able to tell a compelling story about the intellectual and theological debates that divided the western Church at a vulnerable moment in its history. This is such a volume. Ian Christopher Levy offers a valuable, and in many places highly original, re-reading of the disputes normally grouped under the headings of ‘the Wycliffite controversies’, ‘Hussitism’ and ‘conciliarism’: for Levy, what these debates had in common, and what made them virtually unresolvable without recourse to blunt coercive force, was that nearly all the participants were ‘very much part of the establishment’ and accepted Scripture ‘as the principal foundation of authority’ (pp. xii, xi). At the heart of Levy's book is what we might call a ‘chicken and egg’ problem. If everyone agrees that Scripture is the ultimate source of theological truth and authority, what is to be done when different interpretations of Scripture arise, each derived using the same methods and each grounded in patristic texts? If the Church, or the pope, is taken to be the ultimate arbiter, what is to be done if the Church or the pope acts contrary to Scripture? In short: who decides what is authoritative, and how is that judgement to be reached? Over the chapters that form the core of this volume, Levy traces the solutions to this dilemma offered by key participants in the controversies of the late fourteenth and early fifteenth centuries. John Wyclif, in keeping with a recent trend in scholarship (much of which has relied on Levy's other publications on the Oxford scholar), appears here not as ‘the dangerous radical’ of medieval anti-Wycliffite propaganda but rather ‘the traditional university master’ whose theological methods are, ultimately, not significantly different from those of his opponents (p. 55). William Woodford and Thomas Netter are a master-student pair who shared a common desire to reject Wyclif's views but were, in the end, unable to formulate unambiguous methods of their own. Jan Hus, his followers, and his opponents, refreshingly appear as much more complicated figures than scholars have usually admitted: Hus as a theologian in his own right, rather than Wyclif's slavish disciple, and his accusers as ‘contemptible’ antagonists who did not even allow Hus an opportunity to explain himself (p. 175). Finally, Levy presents Jean Gerson and Reginald Pecock as two individuals who did propose solutions to the ‘chicken and egg’ problem – Gerson in his appeal to the general council as ultimate source of authority, and Pecock with his appeal to reason rather than the tradition of scriptural interpretation – but whose proposals met with all but immediate rejection. Levy identifies this book as a work of ‘historical theology’, and he offers more than summary and analysis of the writings of the thinkers that he has chosen (p. xv). Indeed, this volume provides a new, and to this reader highly persuasive, narrative about what rendered these debates so intractable: since the western Church had no single answer to the problem of authority, it was inevitable that theological conflicts would not easily be resolved, and resolving them became harder still when authorities feared the consequences of ‘popular heresy and political insurrection’ in England, Bohemia and elsewhere (p. 235). Levy's treatment is uniformly fair and even-handed: he reveals that the opponents of Wyclif, Hus and other so-called radicals used almost identical theological tools as their fellow scholars, and he concludes that as a result of the instability about authority that he describes, ‘it may be difficult to speak even of dissent, let alone of heresy, in the case of the late medieval university masters’ (p. 235). Levy's book complicates in profound ways standard scholarly narratives not only about ‘heresy’ and ‘dissent’, but also about the various ‘schools’ of late medieval theology. This is a volume the implications of which reach into many disciplines in the study of the late Middle Ages; its impact will be felt for many years to come. It is remarkably free from error of any variety, cleverly organised, and lucidly and carefully written (though its occasionally untranslated Latin quotations may make it difficult to use in the undergraduate classroom). And in a world where Churches of many stripes remain troubled by debates about authority, it offers a clear-eyed look at a period where such debates, left unchecked and fuelled by fear and personal antagonism, had deadly consequences.