Through a close reading of primary texts augmented with historical-critical contextualization, this essay examines the competing approaches of Bonaventure and Aquinas to the disputed question “whether the Body of Christ descends into the stomach of a mouse” to show how the divergent responses of each doctor manifest comtrasting approaches to metaphysics, semiotics, transubstantiation, the theology of revelation, and even Christology. The essay proceeds in four parts. First, I outline the position of Bonaventure as given in his commentary on Book IV of Peter Lombard's Sentences, with references to his sources in Lombard himself and Lothar of Segni (Innocent III). Second, the doctrine of Aquinas—largely consistent from his own Sentences Commentary to the Summa Theologiae—is presented in light of the ius decretalium in force in his time. Third, I provisionally assess the two positions with reference to a consensus among other medieval doctors contemporary with Bonaventure and Aquinas. Fourth, I examine the contrast between Bonaventurean and Thomistic sacramental theology in light of their respective construals of revelation.