a 9th-century-AD controversy between Eastern and Western Christianity that was precipitated by the opposition of the Roman pope to the appointment by the Byzantine emperor Michael III of the lay scholar Photius (Photius, Saint) to the patriarchate of Constantinople. The controversy also involved Eastern and Western ecclesiastical jurisdictional rights in the Bulgarian church, as well as a doctrinal dispute over the Filioque (“and from the Son”) clause that had been added to the Nicene Creed by the Latin church.