Orthodox
What caused the Great Schism of 1054?
A long buildup of theological disagreement (chiefly the Filioque) and cultural, linguistic, and political estrangement between Rome and Constantinople came to a head in 1054 when papal legates and the Patriarch of Constantinople exchanged mutual excommunications, though the split hardened gradually over subsequent centuries.
Catholic teaching
The Catholic Church regards 1054 not as an instantaneous total rupture but as a symbolic flashpoint in a centuries-long drifting apart, and continues to hope and work for full restoration of communion, recognizing genuine faults and failures of charity on both sides in that history.
Biblical foundation
Paul's warning against divisions in the Body of Christ, 'is Christ divided?' (1 Cor 1:13), and his plea that Christians 'be perfectly joined together in the same mind' (1 Cor 1:10) frame the schism as a real wound to the unity Christ willed for his Church.
Scripture references
Historical evidence
On July 16, 1054, Cardinal Humbert laid a bull of excommunication against Patriarch Michael Cerularius on the altar of Hagia Sophia; the patriarch responded in kind days later, though historians note ordinary Christians on both sides likely did not perceive an immediate full break in communion.
The Church Fathers
“We are compelled to bewail the disunion of the churches, since it stirs up brother against brother.”