This book deals with medieval inquisitors’ enigmatic thoughts and feelings as pursuers of heretics. As she explains in her enthusiastic preface, Sullivan's aim is to explore their inner and hidden world through their documents and works, focusing upon their literary sources.

Recent scholarship on the inquisition has focused on the inquisitors more than on the accused, reversing an old historiographical trend that concentrated upon victims. The inquisitors have been overlooked because of the lack of documentation but also because scholars felt closer to the victims. At the end of twelfth century the Church began to transform heresy into a political crime and the birth of the inquisition fulfilled that process of demonising religious dissent. Gradually the attitude of the Church and the theologians towards heretics shifted from charity to zeal, and the latter prevailed, step by step, in the prosecution of heretics, not only by preaching and disputing, but by judging them.

Attempts to perform a social analysis of inquisitors have not yielded much fruit, even if there are interesting outcomes (Marina Benedetti, Inquisitori Lombardi del Duecento, Rome 2009; Michael Tavuzzi, Renaissance inquisitors: Dominican inquisitors and inquisitorial districts in northern Italy, Leiden 2007). Sullivan follows an idiosyncratic path between Moore's concentration on historical circumstances and Nederman's on individuals, because of her interpretative choice to analyse the inquisitors’ attitudes towards heretics. The seven individuals discussed (three of them never were inquisitors) can be separated into two categories, those following the path of zeal and those that of charity: zeal (Bernard of Clairvaux, Conrad of Marburg, Bernard Gui [1261–1331] and Nicholas Eymeric [1320–99]; charity (Dominic Guzmán, Peter Martyr [1203–52] and Bernard Délicieux). Thanks to different sources, Sullivan portrays inquisitors’ charitable or zealous approach towards heretics. These inquisitors lived in different areas and at different times, so their disposition towards the heretics cannot be examined outside their political frameworks and their wider cultural context. The relationships between states and among religious orders significantly altered the perception of the threat of heresy, for instance. The process of heresy-making and of heresy-hunting is influenced and produced by uncertainty and political conflict, so Sullivan's challenging interpretation sometimes seems to be too abstract; however, her claims seem sound and some of her suggestions need to be examined.

Nowadays scholars must tackle what Marina Benedetti defined as ‘the wide variegation in transmitting different forms of the sources of repression’: that is the new challenge.