Quis in tenebris ambulet, quis in luce

The representations of heresy that have been considered so far have all been located in what could loosely be termed a literary context; next to that material, a substantial corpus of legislation against heresy, which formed a distinctive anti-heretical tradition all of its own, was developing. Ultimately, in the mid thirteenth century, that tradition increasingly meant the documentary output of inquisition, but the texts produced by that process will be considered in their own right in the following chapter. This chapter will consider the representation of heresy within the wider tradition of canon law, through conciliar material and through the textbooks of canon law. The former group includes both the canons of the ecumenical councils and especially the canons of the various regional councils, in which many of the more specifically anti-heretical provisions were put in place. Next to the direct legislation must be placed the textbook material that provided the basis for the teaching of canon law, those collections of authorities that informed the wider understanding of the law – namely Gratian's Decretum and the Liber Extra of Gregory IX. A systematic and exhaustive description of the vast legal context of heresy is not the purpose here – there will be no serious consideration of imperial or civil law, for example. Rather, the aim is to delineate the main features of the canon-legal treatment of heresy through an examination of those texts that either are the principal example of their genre or which can be taken as representative.