During the past three decades, the once fashionable thesis that the papacy and the inquisitors who operated under papal authority were primarily responsible for the great European witch-hunt has come under attack. Historians have pointed out the crucial role that secular and episcopal courts played in the early years of witch-hunting, the low number of prosecutions in Italy in the late sixteenth and seventeenth centuries, and the relatively high number of executions in many Protestant countries. Rainer Decker's illuminating study of the papacy's involvement in witch-hunting from the Middle Ages to the nineteenth century represents the most sustained and comprehensive contribution to this revisionism in witchcraft studies. Decker's revisionism, however, bears no signs of confessional bias or special pleading. He fully recognizes, for example, that the papacy did play a role in the formation of the composite notion of witchcraft in the late Middle Ages and that the Inquisition conducted a large number of witchcraft trials in the fifteenth and early sixteenth centuries. But for the period after 1542, when Pope Paul III established the Roman Inquisition, also known as the Holy Office, the papacy's record on witchcraft was marked by theoretical skepticism and judicial restraint. Unlike the medieval Inquisition, which had also operated under papal authority, the Roman Inquisition was a highly centralized institution that exercised jurisdiction over the Italian mainland and a few locations outside Italy. The Dominicans and Franciscans who staffed this institution compiled a remarkably lenient record in prosecuting witches, especially after the death of the intolerant Pope Paul IV in 1559, just as the European witch-hunt was entering its most intense phase. In the city of Rome the Inquisition executed its last witch in 1572, and by the 1630s it stopped prosecuting witches throughout Italy.

Part of the reason for this exceptionally low number of prosecutions and executions was a growing skepticism among jurists and inquisitors regarding the reality of the witches' sabbath, the nocturnal assemblies where large numbers of witches allegedly worshipped the devil and engaged in a variety of immoral activities. Medieval inquisitors had played a role in creating this fantasy, but sixteenth-century demonologists conducted a spirited debate on the subject, which Decker discusses at length. In this debate the skeptical voices of Italian jurists, including Andrea Alciati, fostered a reluctance of Roman inquisitors to accept the testimony of witches. Papal authorities also displayed considerable skepticism regarding the reality of demonic possession, a phenomenon that often led to witchcraft prosecutions. Decker first became aware of this papal attitude toward possession when he discovered a correspondence with the Vatican regarding a witch-hunt in the German city of Paderborn in 1656–57. Decker's research on this case, which he published in 1994, marked the beginning of his work in the previously inaccessible papal records that became his main sources in writing this book.

The Roman Inquisition did prosecute large numbers of offenders for practicing magic. The medieval Inquisition had claimed jurisdiction over magic on the grounds that it involved making a pact with the devil and was therefore heretical. In the late sixteenth century, however, the Roman Inquisition showed little interest in prosecuting offenders for practicing maleficium, or harmful magic, the crime that lay at the core of most witchcraft trials. The main forms of magic that the Inquisition prosecuted were love magic and divination, activities that were not usually linked to witchcraft and did not merit the death penalty. The only magical practices that deserved capital punishment in the Roman Inquisition after 1559 were necromancy, which involved an explicit pact with the devil, and attacks on the Eucharistic host for magical purposes. Even then, few of these cases ended in execution.

The low number of convictions and executions for witchcraft in the Roman Inquisition, just like those of the Spanish Inquisition, owed much to the enforcement of strict procedural rules that recommended caution and discouraged the use of torture. Decker is not the first historian to recognize the Roman Inquisition's cautious approach, but he presents the clearest account of its development in the wake of a conflict over a witchcraft trial in southern Italy in 1593–94. After investigating this witch-hunt, Pope Clement VIII released the accused witches, who had been named by two demoniacs, and prosecuted the local bishop for torturing subjects without sufficient evidence and for failing to appeal the case to Rome. Giulio Monterenzi, the inquisitor whom the Holy Office sent to investigate the incident, then drafted a set of rules for use in witchcraft trials. These instructions were widely distributed in manuscript during the 1620s and published anonymously as the Instruction Concerning Witchcraft Trials in 1657. Rome had more success enforcing these procedural guidelines in its tribunals than in the secular courts, over which Rome could exercise no formal control. The sustained effort of the Holy Office to persuade the secular courts in the trilingual Swiss territories north of the Alps, known as the Grisons, to adopt a more moderate, tolerant approach toward accused witches, especially during a severe witch-hunt in 1654–55, met with only limited success. Moreover, Italian secular courts, like their Spanish counterparts, continued to execute witches well into the eighteenth century. As late as 1780, two years before the last European execution for witchcraft, an inquisitor in Bergamo in northern Italy went to great lengths to secure the release of a witch whom secular authorities in the Grisons had arrested and brutally tortured.

Decker's book, which was originally published in German in 2003, will find its main audience among ecclesiastical and witchcraft historians as well as those interested in the history of criminal justice. Its broad chronological range, references to the broader history of witchcraft in Europe, and excellent translation by H. C. Erik Midelfort also make it suitable for undergraduates encountering the history of witchcraft for the first time.