Abstract: (1) This article explores the uses made of the Biblical story of Malchus's ear in the debate in the eleventh and twelfth centuries about the validity and efficacy of the sacraments of simoniacs. (2) It uses that exploration to argue that an important change occurred in the thirteenth century in the kinds of arguments that canonists made and that the type of argument made about Malchus' ear was also not characteristic of canonical argument prior to the eleventh century. (3) It concludes by suggesting that the type of argument that was made about Malchus' ear is more like the types of arguments made in Jewish and Islamic law than are the types of arguments that are made in canon law in the thirteenth and later centuries. Possible reasons for the difference, in most periods, between canon law, on the one hand, and Jewish and Islamic law, on the other include: the streak of antinominianism that can be found in early Christian writing, the different relationship between religious and secular authority throughout most of the history of the three religions, the difference in the ways in which religious authority is structured in Christianity as opposed to Judaism and Islam, and the tendency of Christianity to separate law and morals more sharply than do Judaism and Islam.