I argue in Chapter 3 that the canon law precept of the marriage debt, which was formulated particularly by Augustine, Gratian, and Thomas Aquinas in the course of establishing marriage as a sacrament, indicates a mode by which power is exercised on and through the bodies and the wills of married parties. It is a mode by which individuals are enjoined to a voluntary subservience. The power that the loathly lady figure wields over the penitent knight in The Wife of Bath’s Tale leaves its subject formally free but freely compliant, aiming at the production of internal conditions rather than external constraints. The same dynamic shapes the plots of other medieval texts featuring the marriage debt, from Chaucer’s The Merchant’s Tale to the tales told on Days 2 and 8 of Boccaccio’s Decameron, all of which I consider as illustrative analogues. These texts identify marriage, and marital sex in particular, as a key site where debt makes subjects, where political power is enacted in and through the free wills of human beings.