Filioque

The Holy Spirit coming from both the Father and the Son, detail of the Boulbon Altarpiece, c. 1450. Originally from the high altar of the Chapelle Saint-Marcellin, Boulbon, France, now in the Louvre, Paris.

Filioque (English pronunciation /ˌfɪliˈoʊkwi, -kweɪ/ FIL-ee-OH-kwee, -⁠kway; Ecclesiastical Latin: [filiˈokwe]) is a Latin term meaning and the Son. The inclusion or omission of this term in the Niceno-Constantinopolitan Creed has been a theological and procedural controversy, a major cause of the schism of 1054 AD between the Western and Eastern churches, and an ongoing source of disagreement for over a thousand years. The clause is inserted in the words Qui ex Patre [Filioque] procedit, 'Who proceeds from the Father [and the Son]', which specifically address the procession of the Holy Spirit, defining whether He proceeds from the Father, or from the Father and the Son (Jesus Christ).

The Nicene Creed was written in Greek, adopted by the First Council of Nicaea in 325 AD, and amended by the First Council of Constantinople in 381 AD. However, the wordings of the creeds adopted at Nicaea and Constantinople are not recorded in any surviving document until the Council of Chalcedon in 451 AD. Christian tradition holds that the Constantinople council added the passage stating that the Holy Spirit 'proceeds from the Father' (τὸ ἐκ του Πατρὸς ἐκπορευόμενον).

The Third Council of Toledo in 589 AD inserted the word Filioque into the creed, in response to the Arian interpretation of the Trinity, which the council considered heretical. Supporters argue that this was merely a clarification of existing theology expressed by the Church Fathers. Opponents argue that it violated Canon VII of the Council of Ephesus (431 AD), which forbade modifications to the creed. The use of Filioque spread to the Frankish church in the 8th century, who claimed that it was an authentic part of the Nicene Creed, so no canon had been violated. Under pressure from Henry II, Holy Roman Emperor, in 1014 AD Pope Benedict VIII incorporated Filioque into the creed used at Rome.

There have been numerous attempts to resolve the conflict, such as by explaining it as a matter of semantics not doctrine, or by appealing to the early seventh century work of Maximus the Confessor who is accepted by both sides.