In recent years, thanks to the groundbreaking work of Marcia Colish, scholars have begun to take Peter Lombard more seriously as a theologian in his own right and not just as a mere compiler of the Sentences. Clare Monagle's monograph makes a valuable contribution to our understanding of both the Lombard's theology and the status of his famous textbook through an exploration of a simple but illuminating question: how did this work overcome its early critics to become the foundation of theological education for the next several centuries, and its author's Trinitarian theology, contested for several decades after his death, receive such a resounding endorsement at the Fourth Lateran Council? Monagle draws upon R. I. Moore's thesis about the twelfth-century rise to power of the clerici to frame her investigation. She argues that Lateran IV's support for the Lombard's theology is emblematic of this wider triumph of the clerici and their modes of thought. Precisely what this triumph meant for theology, and its role within the Church, is suggested in chapter i where Monagle traces a series of intellectual controversies, from Berengar of Tours to Gilbert of Poitiers. These controversies foreshadowed issues that would arise in contests over the Lombard and his work, especially in the case of those who complained that the schoolmen were undermining the faith by using grammatical tools to understand divine things. In chapter ii, after situating the Lombard within the mid twelfth-century context of the schools, Monagle shows how he cannily cultivated important relationships with critics like Bernard of Clairvaux while nevertheless constructing his own work along the lines of those whom he outwardly criticised. Chapters iii and iv explore criticisms of both the Lombard and the Sentences. Monagle's most important observations here concern the continuity of these criticisms with those made against the Lombard's scholastic predecessors. The Lombard's critics were focused as much or more on his methods as on anything actually contained in the Sentences. Some criticisms (such as that the Lombard was a Christological nihilist) were even erroneous. Yet, as Monagle explains, these misreadings are not merely evidence of the critics' shallow misundertanding of the Lombard. They also reflect just how threatening some individuals perceived the rigorously technical terminology of the schools to be. Yet, as chapter v argues, Lateran IV endorsed the Lombard and his methods precisely because his innovations helped to provide the intellectual tools for accomplishing the practical reform programme envisioned by Peter the Chanter's generation, of which the council's decrees were an extension. While Monagle might usefully have expanded her treament beyond the (at times narrow) terms of her study, her arguments are well articulated and largely persuasive. She also succeeds in writing clearly, making otherwise difficult debates intelligible. This book will be useful for a range of readers interested in the history of ideas and in the important transformations of the twelfth and early thirteenth centuries.