Malum non vitatur nisi cognitum

After the letters and sermons that greeted the first mutterings of dissent in the eleventh century, by the mid twelfth the anti-heretical treatise had re-emerged in the medieval west with the quickening of heresy and the growth of the schools. Early attempts, with the possible exception of Peter the Venerable's Contra petrobrusianos, tended to remain within the sheltering framework of previously condemned heresy provided by the early church: Eckbert of Schönau's Sermones tredecim contra haereticos of 1163–7, the first major work on dualist heresy in the Middle Ages, nevertheless drew heavily on Augustine's Contra manicheos for authority and content.

The new trend in polemic, which moved away from a patristic and towards a more identifiably ‘high-medieval’ mode, began in earnest around the turn of the century. The confession of the convert Bonacursus was reworked as a polemical tract against the Cathars; a text against Cathars and Passagians produced in Italy was an early scholastic response to heresy; and medieval anti-heretical polemic found its first known full-scale expression in Alan de Lille's De fide catholica contra haereticos sui temporis of 1199–1202, a four-book text that deals with heretics alongside other enemies of the church, here Jews and Muslims. Several mostly French works on heresy survive from the early years of the thirteenth century, perhaps most importantly the later work of Durand of Huesca, a former follower of Valdes, against the Cathars.