«De novitate et necessitate processit»: la fondazione della diocesi di Alessandria

This paper analyses the foundation of the Diocese of Alessandria (1175), focusing not so much on reconstructing the political and institutional events or on the territorial definition of the new episcopal see, but rather on the canonical prerequisites that made the creation ex novo of a bishopric possible. Drawing on the documentation of Alexander III, and in particular the formula De novitate et necessitate processit, the essay identifies the foundation of the diocese as the true novitas of the entire affair, distinguishing it from the appointment of the first bishop, Arduino, which, whilst exceptional in its manner, was justified by papal prerogatives and the absence of a cathedral chapter. The study is developed through an analysis of the main medieval canonical collections, from late antique compilations to Gratian’s Decretum, with the support of the Clavis Canonum database. It emerges that, up until the 11th century, canon law was confined mainly to reaffirming the principle of the stability of diocesan circumscriptions, without establishing specific rules governing the foundation of new dioceses. It was only with the Gregorian Reform, through the Dictatus papae, the Propriae auctoritates apostolicae sedis and the canonical collections of the Gregorian school, that the principle gradually took hold that the creation of new bishoprics constituted an exclusive prerogative of the Roman Pontiff. Finally, the case of Alexandria is placed within a broader comparison with other diocesan foundations in Italy and the Empire (Bamberg, Bobbio, Brugnato), highlighting how the Diocese of Alexandria represents a significant milestone in the process of consolidating the papacy’s jurisdictional primacy in matters of ecclesiastical organisation.