Sister churches, hermeneutical principle in relations between Churches ad intra and ad extra

This article by Barbara Hallensleben examines the concept of "sister Churches" as a hermeneutical principle structuring ecclesial relations, both within Orthodoxy and between Orthodox and Catholic Churches. Presented in the form of theses, the study traces the evolution of the term from the Second Vatican Council to recent magisterial documents, showing the progressive convergence between the notions of particular Church and sister Church. The central idea is that this principle of sacramentality goes beyond a purely territorial framework and implies a constitutive orientation toward full communion. The article makes a twofold theological contribution: on the one hand, it identifies the unfinished reforms within post-conciliar Catholicism; on the other hand, it addresses precise questions to the Orthodox Churches regarding the visible realization of the transterritorial principle, particularly in view of the preparation for the Pan-Orthodox Council.