The council was called by Emperor Basil I the Macedonian, with the support of Pope Hadrian II.

[3] It deposed and anathemized Photius,[4] a layman who had been appointed as Patriarch of Constantinople, and reinstated his predecessor Ignatius.

Whether and how far the Greek Fourth Council of Constantinople was confirmed by Pope John VIII is a matter of dispute.

In 858, Photius, a noble layman from a local family, was appointed Patriarch of Constantinople, the most senior episcopal position save only that of Rome.

Specifically, its third Canon required the image of Christ to have veneration equal with that of the gospel book:[20] We decree that the sacred image of our Lord Jesus Christ, the liberator and Savior of all people, must be venerated with the same honor as is given the book of the holy Gospels.

For as through the language of the words contained in this book all can reach salvation, so, due to the action which these images exercise by their colors, all wise and simple alike, can derive profit from them.