The Fourth Lateran Council's Non debet (c.50) and the Abandonment of the System of Derived Affinity

Abstract

At the beginning of the thirteenth century important changes were introduced to kinship rules in Latin Christianity. One of them was a new principle operating in canon law after the Fourth Lateran Council had amended the regime of impediments to marriage. In addition to reducing impediments to the fourth degree in the case of consanguineous unions and unions of affinity, the constitution Non debet (c.50) abandoned the system of derived affinity. The system in force until 1215 defined affinity bonds of a second and third genus. Non debet implied the enforcement of a new principle, later summarized in the adage affinitas non parit affinitatem, meaning that, if a man had intercourse with a woman, the man became related to the woman´s relatives but the man´s relatives did not derivatively become relatives of the woman´s relatives. This paper aims to analyse these changes in connection with two homologous formulae of the medieval learned world: pecunia pecuniam non parit and fictio non parit fictionem. Both dealt with the relations between nature and the artifice of institutional constructions. The correlation of the three adages may enable us to take a glimpse at a common paradigm concerning the limits of fictional construction in the Middle Ages.