Abstract
Scholars typically view Causa 23 of Gratian’s Decretum within a vacuum, looking solely at the nature of a just war or the Church’s coercive powers. When one considers, however, that Gratian used the first recension of the Decretum for teaching, a more complex picture comes to light. Causa 23 fits into a tract on substantive law (i.e. law of obligations) comprising of Causa 22–Causa 26. Serving as the anchor of the tract, Causa 22 sets down the social norms of the oath whereby each party must ensure the integrity of the oath by fulfilling the requisite obligations and avoiding perjury. Employing these societal principles, this chapter argues that Causa 23 can be read as a case dealing with the practical nature of investiture. As bishops, prelates owed obedience to the pope, ministered to their flocks, and served as judges in ecclesiastical court. The bishops, however, had received civil jurisdiction from the emperor—that is, the emperor had invested them as lay lords—and thus they were expected to fulfill feudal obligations, such as military service and serving as judges in secular court. Gratian sought to teach students how, as future bishops, they should balance their ecclesiastical obligations with the military and judicial obligations required as feudal vassals and lords. In order to do this Gratian employs a particular pedagogical technique of organizing material according to a “theoretical approach and application of the approach” model. Gratian devotes particular questions to a definition of or a justification for the law—that is, the theory behind the law—while he devotes other questions to execution of the law—that is, how the law should be applied. Setting forth the philosophical underpinnings that military service and thus the waging of wars were justified, secular benefices were permitted to be used in defense of the Church and, while obligations were owed to the emperor, they could not be fulfilled in violation of the obligations owed to the pope. Echoing the Concordat of Worms (1122) that ended the Investiture Controversy, Gratian illustrated how a bishop could hold both an ecclesiastical and a secular benefice. He simply had to know when to wear which hat.