Council of Constantinople (867)

The Council of Constantinople of 867 was a major Church Council, convened by Emperor Michael III of Byzantium and Patriarch Photios I of Constantinople in order to address several ecclesiastical issues, including the question of Papal supremacy in the Church, and the use of Filioque clause in the Creed.

Pope Nicholas I had attempted to remove Photios and reappoint Ignatius as the Patriarch of Constantinople by his own authority and decree.

Thus, the Pope was intervening in matters of Imperial authority as well as in the other churches of the East and their own internal councils and authorities, which they understood to be outside the Pope's own jurisdiction of Rome (and perhaps the rest of the West; at the time of these councils there were no other Patriarchs in the West other than Rome, whereas there were four Patriarchs of the East).

The Council at Constantinople in 867 excommunicated Pope Nicholas I and declared him anathema.

[5] In addition, Roman claims of papal primacy, his contacts with Bulgaria,[5] and the Filioque clause were condemned.