A. Van Bunnen

This article constitutes the concluding part of a historical and ecclesiological study devoted to the Council of Constantinople of 879-880, which sealed the reconciliation between Rome and Constantinople following the Photian controversy. Drawing on a critical analysis of the conciliar Acts and on the works of Dvornik, Van Bunnen examines the Byzantine conception of Roman primacy as it manifests itself in the debates of the council. He shows that Photius, contrary to a historiographical tradition long hostile to him, acknowledged Rome's position as *primus inter pares*, grounded in a charismatic and fraternal principle rather than a jurisdictional one. The main contribution of the article is to demonstrate that the ninth-century East did not oppose Roman primacy to collegiality, but articulated them within an ecclesiology of communion, whose structural ambiguities — notably the pentarchic system — nonetheless carried within them the seeds of later divisions.