My research focuses on late medieval religious history, particularly the history of magic, witchcraft, and superstition, as well as heresy and religious reform. I also study the history of magic globally from antiquity to the present day. My work has appeared in such journals as Speculum, the journal of the Medieval Academy of America, and the American Historical Review. I have written four books, the most recent of which is Fearful Spirits, Reasoned Follies: The Boundaries of Superstition in Late Medieval Europe, published by Cornell University Press in 2013, and I edited a multi-volume collection, Magic and Witchcraft: Critical Concepts in Historical Studies, published by Routledge in 2014. I am currently completing another book for Routledge, Magic: The Basics, and I serve as an editor of the interdisciplinary journal Magic, Ritual, and Witchcraft, which I helped to found in 2006. Over the course of my career I have held Fulbright, DAAD, and Humboldt fellowships abroad, as well as a Mellon Fellowship at the University of Pennsylvania and a Solmsen Fellowship at the University of Wisconsin-Madison. My current major research project, tentatively titled Religious Falsity in an Age of Faith, examines multiple forms of religious “error” in medieval Europe from the Gregorian Reform to the Reformation, including clerical corruption, heresy, questionable mysticism, and magic.