Fourth Council of Constantinople

The Fourth Council of Constantinople was the 8th Ecumenical Council. In accordance to the Roman Catholic Church, it was held in Constantinople from October 5, 869 to February 28, 870. It included 102 bishops, 3 papal legates, and 4 patriarchs. The Council met in 10 sessions from October 869 to February 870 and issued 27 canons.

The council was called by Emperor Basil I the Macedonian and Pope Adrian II. It deposed Photios, a layman who had been appointed as Patriarch of Constantinople, and reinstated his predecessor Ignatius.

The Council also reaffirmed the decisions of the Second Council of Nicaea in support of icons and holy images and required the image of Christ to have veneration equal with that of the gospel book.

A later council, the Greek Fourth Council of Constantinople, was held after Photios had been reinstated on order of the Emperor. This council, comprising the representatives of all the five patriarchates, including that of Rome (all in all 383 bishops), reinstated Photius as Ecumenical Patriarch and annulled the earlier one. The council also condemned any alteration whatsoever to the original Nicene-Constantinopolitan Creed, thereby condemning the addition of the Filioque clause to the creed as heretical.

Today, the Roman Catholic Church recognizes the council in 869-870 as "Constantinople IV", while the Eastern Orthodox Churches recognize the councils in 879-880 as "Constantinople IV" and revere Photios as a saint. At the time that these councils were being held, this division was not yet clear. These two councils represent a break between East and West. The previous seven ecumenical councils are recognized as ecumenical and authoritative by both Greek-literate Eastern Christians and Latin-literate Western Christians. This division led eventually to the East-West Schism of 1054.

Fourth Council of Constantinople in Agent of Byzantium
The Fourth Council of Constantinople condemned the doctrine of dual possession of the Holy Spirit as heterodox. However, the Northern European followers of the line of popes deposed by Emperor Constans II did not view this council as Ecumenical and so continued to include the Filioque clause in their Masses. Citizens of the Empire travelling in the Franco-Saxon Kingdoms, who attended these Masses, frequently assuaged their consciences by remaining mute during the Filioque.