Filioque

===Procession of the Holy Spirit===
As early as the 4th century, a distinction was made, in connection with the Trinity, between the two Greek verbs {{lang|grc|ἐκπορεύεσθαι}} (the verb used in the original Greek text of the 381 Nicene Creed) and {{lang|grc|προϊέναι}}. [[Gregory of Nazianzus]] wrote: "The Holy Ghost is truly Spirit, coming forth ({{lang|grc|προϊέναι}}) from the Father indeed, but not after the manner of the Son, for it is not by Generation but by Procession ({{lang|grc|ἐκπορεύεσθαι}})".{{refn|Gregory of Nazianzus ''Oratio 39'' 12 ([[s:Nicene and Post-Nicene Fathers: Series II/Volume VII/Orations of Gregory Nazianzen/Oration 39|NPNF2 7:356]]).}}

That the Holy Spirit "proceeds" from the Father and the Son in the sense of the [[Latin]] word {{lang|la|procedere}} and the [[Greek language|Greek]] {{lang|grc|προϊέναι}} (as opposed to the Greek {{lang|grc|ἐκπορεύεσθαι}}) was taught by the early 5th century by [[Cyril of Alexandria]] in the East.{{sfn|ODCC|2005|loc="Double Procession of the Holy Spirit"}}{{refn|Cyril of Alexandria, ''Thesaurus'', (PG 75:585).}} The [[Athanasian Creed]], probably composed as early as the mid 5th-century,<ref>{{cite web|last=Krueger|first=Robert H.|year=1976|title=The origin and terminology of the Athanasian Creed|website=wlsessays.net|publisher=Wisconsin Lutheran Seminary Digital Library|url=http://hdl.handle.net/123456789/2744|archive-url=https://web.archive.org/web/20151109062820/http://www.wlsessays.net/bitstream/handle/123456789/2744/KruegerOrigin.pdf|archive-date=9 November 2015|url-status=dead|id=Presented at Western Pastoral Conference of the Dakota-Montana District, Zeeland, ND, 5–6 October 1976}}</ref> and a dogmatic epistle of [[Pope Leo I]],{{refn|name=LeoI447|Pope Leo I ''Quam laudabiliter'' c. 1 (PL 54:680–681); {{harvnb|DH|2012|loc=n. 284}}}}<ref name="CCC247">{{Cite CCC|2.1|247}}</ref>{{efn|"The Holy Ghost is from the Father and the Son, neither made, nor created, nor begotten, but proceeding". In the original Latin: "{{lang|la|Spiritus Sanctus a Patre et Filio: non-factus, nec creatus, nec genitus, sed procedens}}".}} who declared in 446 that the Holy Spirit proceeds from both Father and Son.<ref name="CCC247"/>

Although the Eastern Fathers were aware that the procession of the Holy Spirit from the Father and the Son was taught in the West, they did not generally regard it as heretical.{{sfn|Dulles|1995|pp=32, 40}} According to [[Sergei Bulgakov]] "a whole series of Western writers, including popes who are venerated as saints by the Eastern church, confess the procession of the Holy Spirit also from the Son; and it is even more striking that there is virtually no disagreement with this theory."{{sfn|Bulgakov|2004|p=90}} In 447, Leo I taught it in a letter to a Spanish bishop and an anti-[[Priscillianism|Priscillianist]] council held the same year proclaimed it.{{refn|name=LeoI447}} The argument was taken a crucial step further in 867 by the affirmation in the East that the Holy Spirit proceeds not merely "from the Father" but "from the Father {{em|alone}}".{{sfn|Guretzki|2009|p=8}}{{sfn|Bulgakov|2004|p=95}}

The {{lang|la|Filioque}} was inserted into the Creed as an anti-Arian addition,{{sfn|Marthaler|2001|pp=248–249}}{{sfn|Irvin|Sunquist|2001|p=340}}{{sfn|Dix|2005|pp=485–488}} by the [[Third Council of Toledo]] (589), at which King [[Reccared I]] and some [[Arians]] in his [[Visigothic Kingdom]] converted to orthodox, Catholic Christianity.{{sfn|Hinson|1995|p=220}}{{sfn|Louth|2007|p=142}}{{efn|While Reccared I converted to Catholicism, his successor [[Liuva II]] reverted to Arianism.{{sfn|Hinson|1995|p=220}}}} The Toledo XI synod (675) included the doctrine but not the term in its profession of faith.{{sfn|DH|2012|loc=n. 527}}

Other Toledo synods "to affirm Trinitarian consubstantiality" between 589 and 693.{{sfnm|PCPCU|1995|DH|2012|2loc=nn. 470, 485, 490, 527, 568}}

The {{lang|la|Filioque}} clause was confirmed by subsequent synods in Toledo and soon spread throughout the West, not only in Spain, but also in [[Francia]], after [[Clovis I]], king of the [[Salian Franks]], converted to Christianity in 496; and in England, where the [[Council of Hatfield]] (680), presided over by Archbishop of Canterbury [[Theodore of Tarsus]], a Greek,{{sfn|Siecienski|2010|p=88}} imposed the doctrine as a response to [[Monothelitism]].{{sfn|Plested|2011}}

However, while the doctrine was taught in Rome, the term was not professed liturgically in the Creed until 1014.{{sfn|PCPCU|1995}}

In the [[Vulgate]] the Latin verb {{lang|la|procedere}}, which appears in the {{lang|la|Filioque}} passage of the Creed in Latin, is used to translate several Greek verbs. While one of those verbs, {{lang|grc|ἐκπορεύεσθαι}}, the one in the corresponding phrase in the Creed in Greek, "was beginning to take on a particular meaning in Greek theology designating the Spirit's unique mode of coming-to-be [...] {{lang|la|procedere}} had no such connotations".{{sfn|Siecienski|2010|p=59}}

Although [[Hilary of Poitiers]] is often cited as one of "the chief patristic source(s) for the Latin teaching on the {{lang|la|filioque}}", Siecienski says that "there is also reason for questioning Hilary's support for the {{lang|la|Filioque}} as later theology would understand it, especially given the ambiguous nature of (Hilary's) language as it concerns the procession."{{sfn|Siecienski|2010|p=53}}

However, a number of [[Latin Church]] Fathers of the 4th and 5th centuries explicitly speak of the Holy Spirit as proceeding "from the Father and the Son", the phrase in the present Latin version of the Nicene Creed. Examples are what is called the creed of Pope Damasus I,{{sfn|Siecienski|2010|p=57}} [[Ambrose of Milan]] ("one of the earliest witnesses to the explicit affirmation of the Spirit's procession from the Father {{em|and}} the Son"),{{sfn|Siecienski|2010|p=57}} Augustine of Hippo (whose writings on the Trinity "became the foundation of subsequent Latin trinitarian theology and later served as the foundation for the doctrine of the {{lang|la|filioque}}").{{sfn|Siecienski|2010|p=59}} and Leo I, who qualified as "impious" those who say "there is not one who begat, another who is begotten, another who proceeded from both [{{lang|la|alius qui de utroque processerit}}]"; he also accepted the [[Council of Chalcedon]], with its reaffirmation of the [[Niceno-Constantinopolitan Creed]], in its original "from the Father" form,{{sfn|Siecienski|2010|pp=63–64}} as much later did his successor [[Pope Leo III]] who professed his faith in the teaching expressed by the {{lang|la|Filioque}}, while opposing its inclusion in the Creed.{{sfn|Plested|2011}}

Thereafter, [[Eucherius of Lyon]], [[Gennadius of Massilia]], [[Boethius]], [[Agnellus, Bishop of Ravenna]], [[Cassiodorus]], [[Gregory of Tours]] are witnesses that the idea that the Holy Spirit proceeds from the Son was well established as part of the (Western) Church's faith, before Latin theologians began to concern themselves about {{em|how}} the Spirit proceeds from the Son.{{sfn|Siecienski|2010|pp=64–66}}

[[Pope Gregory I]] is usually counted as teaching the Spirit's procession from the Son, although Byzantine theologians, quoting from Greek translations of his work rather than the original, present him as a witness against it, and although he sometimes speaks of the Holy Spirit as proceeding from the Father without mentioning the Son. Siecienski says that, in view of the widespread acceptance by then that the Holy Spirit proceeds from the Father and the Son, it would be strange if Gregory did not advocate the teaching, "even if he did not understand the {{lang|la|filioque}} as later Latin theology would – that is, in terms of a 'double procession'."{{sfn|Siecienski|2010|pp=70–71}}