What was witchcraft? Were witches real? How should witches be identified? How should they be judged? Towards the end of the middle ages these were new questions, without answers hallowed by time and authority. Between 1430 and 1500, a number of learned "witch-theorists" attempted to provide the answers, and of these perhaps the most famous are the Dominican inquisitors Heinrich Institoris and Jacob Sprenger, the authors of the Malleus Maleficarum, The Hammer of Witches. This, the first book-length study of the Malleus in English, provides students and scholars with an introduction to this text and to the conceptual world of its authors. Ultimately, this book argues that although the Malleus was a highly idiosyncratic text, with a view of witches very different from that of competing authors, its arguments were powerfully compelling and so remained influential long after alternatives were forgotten.