858–880

The Photian Schism

After the deposition of Patriarch Ignatios, the lay intellectual Photios was raised to the see of Constantinople in 858. Pope Nicholas I refused to recognize his election. He overturned his own legates' ruling and demanded Ignatios's restoration. In 867 Photios responded by excommunicating Nicholas I. He declared the whole West heretical for adding the Filioque to the creed.

The dispute concerned not only the legality of Ignatios's deposition but the very principle of primacy. In his treatise "Against the Primacy" Photios argued that Peter had been bishop of Antioch before Rome. True primacy, he held, belonged to Jerusalem. Nicholas I, for his part, upheld Rome's headship over all churches and councils.

After both men's deaths the rivalry continued. There was the council of 869–870, then Photios's return to the see and the council of 879–880. All this showed the growing rift between Rome and Constantinople. It foreshadowed the final break of 1054.

Later, c. 883, Photios set out the Western doctrine of the Spirit's procession from the Son at length in "On the Mystagogy of the Holy Spirit".