Abstract: This chapter traces how impotence magic found a recognized place in the canon law and theology of marriage. This happened because it was incorporated into two works that became standard university textbooks on canon law and theology: the Decretum of Gratian and the Sentences of Peter Lombard. The chapter argues that 12th-century commentators focused mostly on whether the canon law for impotence magic (established by Hincmar of Rheims) was valid, under what circumstances an annulment could be granted, and how allegations of impotence could be proved, although a few also claimed to have encountered real cases. It also surveys the few 12th-century medical writers who discussed impotence magic, including Urso of Salerno, who offered a physical explanation for a phenomenon that other authors ascribed to magic.

Keywords: annulment, canon law, commentaries, Gratian, Hincmar of Rheims, marriage, Peter Lombard, theology, Urso of Salerno,