12 Feb 2026 (Thursday) – Prof. Jonathan Harris – Professor of the History of Byzantium, Royal Holloway, University of London – 1054 and the Schism between the Orthodox and Catholic Churches.
Professor Harris, an expert on the Byzantine Empire, will shed light on one of the most significant events in Christian history: the Great Schism of 1054. This event marked the formal split between the Eastern Orthodox and Western Catholic Churches. While sometimes seen as a sudden break, the schism was the culmination of centuries of theological, political, and cultural disagreements between Constantinople and Rome. Professor Harris’s lecture will explore the long-term causes and immediate triggers of the split, as well as its profound and lasting consequences for Christendom.
Over the past sixty years, scholars have consistently argued against the idea that the excommunication of the patriarch of Constantinople by three papal legates in July 1054 marked the final break between the Churches of East and West. Rather the breach between Catholic and Orthodox should be dated to after 1096 when the crusades increased tension and misunderstanding between Latins and Greeks. While that broad conclusion is probably correct as far as dogmatic and liturgical matters are concerned, the ideological significance of the events of 1054 has been neglected. This article argues that they were both a symptom and, to some extent, a cause of a process of change whereby the ideological claims of the Byzantine emperor became unacceptable to an ever wider section of influential western European opinion. That change manifested itself very strongly at the time of the First Crusade but it had been developing long before that as a result of the widely disseminated propaganda of the reforming papacy. [Abstract to ‘The “Schism” of 1054 and the First Crusade’ by Jonathan Harris]