Jean Baptiste de Boyer d'Argens, clandestine philosophical pornographer, author of the salacious Thérèse Philosophique and other fictionalizations of rationalist philosophy, once ridiculed theology like this: "It is a very sad thing that almost all theologians abuse the Scriptures … [T] he divergent expositions of Jerome, of Luther, of Calvin , of [the Jesuit Pasquier] Quenel, … have troubled all of Europe, and trouble her again," he wrote in 1737. The alleged abusers often repeated the very same complaint, if only applying it to their enemies. The English Recusant Jack Feckenham (d. 1584) noted the fractiousness opened when bishops answering to kings unbridled theologians from ecclesiastical restraint. Theodore Beza (d. 1605) countered that Catholic "sects" and "the rabble of Jesuits, and other such like fellows" were the actual source of confusion. They should all be read against the grain of their complaints. What the Enlightener and theologians alike tacitly acknowledged was the true force of theological practice, as a form of intellectual engagement, not purely the confession, assertion, or defense of singular, incompatible truths. As a practice of knowledge production in schools, theolgians "gamified" thought. This required passionately defended differentiations, if theological knowledge was to exist at all. Every theological position depended on its opposites. No position could exist without the alternatives it strove to deny. The opposites existed on a scale of relative differentiation. This paper offers three examples from the fifteenth and sixteenth centuries (the fifteenth-century Conciliarist Juan de Segovia on Catholicity and Islam, Martin Luther on Catholicity and Judaism, and the Louvain Jesuit Thomas Stapleton on Catholicity and Protestants) to argue that the practice of theology in the past has more significance for Catholicities in the present than doctrine as such.