The Synod of Constantinople 879–880 as a witness to the ecclesiology of communion: The horos, canons and the problem of the boundaries of orthodoxy

Abstract

This article argues that the Synod of Constantinople 879–880 constitutes a significant witness to an early medieval ecclesiology of communion, in which doctrinal fidelity, canonical order and ecclesial reconciliation are held together within a single conciliar grammar. Rather than treating the synod merely as an episode in the so-called Photian conflict or as a secondary chapter in the history of East–West estrangement, the study interprets its horos [conciliar doctrinal definition] and canons as theological sources for understanding the boundaries of orthodoxy, the role of the Nicene-Constantinopolitan Creed, the restoration of ecclesial communion and the contested relation between primacy and synodality. The article proceeds through a close hermeneutical reading of the conciliar material preserved in the critical tradition, with particular attention to the Greek horos, the three canons and the broader reception of the council in Byzantine and Latin memory. It argues that Constantinople 879–880 presents communion not as a merely juridical arrangement, but as a doctrinally normed and sacramentally meaningful reality grounded in fidelity to the inherited confession of faith. The prohibition of additions to the Creed, the rehabilitation of Photius and the regulation of episcopal discipline are therefore read as mutually connected expressions of a theology of ecclesial unity.
Contribution: By interpreting the Synod of Constantinople 879–880 as a theological locus for the study of communion, primacy and doctrinal boundaries, this article contributes to historical theology, conciliar studies and contemporary Orthodox–Catholic reflection. It proposes that the synod should be read not only as a contested event of ninth-century ecclesiastical politics, but also as a paradigmatic case of how the Church negotiates unity, memory and orthodoxy through conciliar discernment.