Filioque

===Claims of authenticity===
At the end of the 8th and the beginning of the 9th century, the Church of Rome was faced with an unusual challenge regarding the use of Filioque clause. Among the Church leaders in Frankish Kingdom of that time a notion was developing that Filioque clause was in fact an authentic part of the original Creed.{{sfn|Siecienski|2010|p=92}} Trying to deal with that problem and its potentially dangerous consequences, the Church of Rome found itself in the middle of a widening rift between its own Daughter-Church in Frankish Kingdom and Sister-Churches of the East. Popes of that time, [[Pope Hadrian I|Hadrian I]] and [[Pope Leo III|Leo III]], had to face various challenges while trying to find solutions that would preserve the unity of the Church.{{sfn|Meyendorff|1996|p=38}}

First signs of the problems were starting to show by the end of the reign of Frankish king [[Pepin the Short]] (751–768). Use of the {{lang|la|Filioque}} clause in the Frankish Kingdom led to controversy with envoys of the Byzantine Emperor [[Constantine V]] at the Synod of Gentilly (767).{{sfn|Maas|1909}}{{sfn|Hinson|1995|p=315}}{{sfn|Siecienski|2010|p=90}} As the practice of chanting the interpolated Latin {{lang|la|Credo}} at [[Mass (liturgy)|Mass]] spread in the West, the {{lang|la|Filioque}} became a part of [[Latin liturgical rites|Latin liturgy]] throughout the Frankish Kingdom. The practice of chanting the Creed was adopted in Charlemagne's court by the end of the 8th century and spread through all of his realms, including some northern parts of Italy, but not to Rome, where its use was not accepted until 1014.{{sfn|Dix|2005|pp=485–488}}{{sfn|Louth|2007|p=142}}

Serious problems erupted in 787 after the [[Second Council of Nicaea]] when Charlemagne accused the Patriarch [[Tarasios of Constantinople]] of infidelity to the faith of the First Council of Nicaea, allegedly because he had not professed the procession of the Holy Spirit from the Father "and the Son", but only "through the Son". [[Pope Adrian I]] rejected those accusations and tried to explain to the Frankish king that pneumatology of Tarasios was in accordance with the teachings of the holy Fathers.{{sfn|Siecienski|2010|p=91}}{{sfn|Nichols|2010|p=237}}{{efn|Charlemagne's legates claimed that Tarasius, at his installation, did not follow the Nicene faith and profess that the Spirit proceeds from the Father and the Son, but confessed rather his procession from the Father {{em|through the Son}} (Mansi 13.760). The Pope strongly rejected Charlemagne's protest, showing at length that Tarasius and the Council, on this and other points, maintained the faith of the Fathers (ibid. 759–810).}} Surprisingly, efforts of the pope had no effect.

The true scale of the problem became evident during the following years. The Frankish view of the {{lang|la|Filioque}} was emphasized again in the {{lang|la|[[Libri Carolini]]}}, composed around 791–793.{{efn|Following this exchange of letters with the pope, Charlemagne commissioned the {{lang|la|Libri Carolini}} (791–793) to challenge the positions both of the iconoclast council of 754 and of the Council of Nicaea of 787 on the veneration of icons. Again because of poor translations, the Carolingians misunderstood the actual decision of the latter Council.{{sfn|NAOCTC|2003}}}} Openly arguing that the word {{lang|la|Filioque}} was part of the Creed of 381, the authors of {{lang|la|Libri Carolini}} demonstrated not only the surprising lack of basic knowledge but also the lack of will to receive right advice and counsel from the Mother-Church in Rome. Frankish theologians reaffirmed the notion that the Spirit proceeds from the Father and the Son, and rejected as inadequate the teaching that the Spirit proceeds from the Father {{em|through the Son}}.{{sfn|Siecienski|2010|pp=91–93}}{{sfn|Nichols|2010|p=237}} That claim was both erroneous and dangerous for the preservation of the unity of the Church.

In those days, another theological problem appeared to be closely connected with the use of {{lang|la|Filioque}} in the West. In the late 8th century, a controversy arose between Bishop [[Elipandus of Toledo]] and [[Beatus of Liébana]] over the former's teaching (which has been called [[Spanish Adoptionism]]) that Christ in his humanity was the adoptive son of God. Elipandus was supported by Bishop [[Felix of Urgel]]. In 785, Pope Hadrian I condemned the teaching of Elipandus. In 791, Felix appealed to Charlemagne in defense of the Spanish Adoptionist teaching, sending him a tract outlining it. He was condemned at the Synod of Regensburg (792) and was sent to Pope Hadrian in Rome, where he made of profession of orthodox faith, but returned to Spain and there reaffirmed Adoptionism. Elipandus wrote to the bishops of the territories controlled by Charlemagne in defence of his teaching, which was condemned at the [[Council of Frankfurt]] (794) and at the Synod of [[Friuli]] (796). The controversy encouraged those who rejected Adoptionism to introduce into the liturgy the use of the Creed, with the {{lang|la|Filioque}}, to profess belief that Christ was the Son from eternity, not adopted as a son at his baptism.{{sfn|Siecienski|2010|pp=93–94}}{{sfn|Dales|2013|pp=61–67}}

At the Synod of Friuli, [[Paulinus II of Aquileia]] stated that the insertion of {{lang|la|Filioque}} in the 381 Creed of the [[First Council of Constantinople]] was no more a violation of the prohibition of new creeds than were the insertions into the 325 Creed of the [[First Council of Nicaea]] that were done by the First Council of Constantinople itself. What was forbidden, he said, was adding or removing something "craftily [...] contrary to the sacred intentions of the fathers", not a council's addition that could be shown to be in line with the intentions of the Fathers and the faith of the ancient Church. Actions such as that of the First Council of Contantinople were sometimes called for in order to clarify the faith and do away with heresies that appear.{{sfn|Siecienski|2010|p=93}}{{sfn|Nichols|2010|p=238}}{{sfn|Kelly|2014|p=364}} The views of Paulinus show that some advocates of Filioque clause were quite aware of the fact that it actually was not part of the Creed.{{sfn|Nichols|2010|p=238}}

Political events that followed additionally complicated the issue. According to [[John Meyendorff]],{{sfn|Meyendorff|1996|pp=41–43, 195–197}} and [[John Romanides]]<ref name="Romanides1">{{cite web|last=Romanides|first=John S.|title=Franks, Romans, feudalism, and doctrine|website=romanity.org|url=http://www.romanity.org/htm/rom.03.en.franks_romans_feudalism_and_doctrine.03.htm}}</ref> the Frankish efforts to get new [[Pope Leo III]] to approve the addition of {{lang|la|Filioque}} to the Creed were due to a desire of [[Charlemagne]], who in 800 had been crowned in Rome as Emperor, to find grounds for accusations of heresy against the East. The Pope's refusal to approve the interpolation of the {{lang|la|Filioque}} into the Creed avoided arousing a conflict between East and West about this matter. During his reign ({{Reign|795|816|lk=abbr}}), and for another two centuries, there was no Creed at all in the [[Roman rite]] Mass.

Reasons for the continuing refusal of the Frankish Church to adopt the positions of the Church of Rome on necessity of leaving Filioque outside of Creed remained unknown. Faced with another endorsement of the Filioque clause at the Frankish [[Council of Aachen (809)]] pope Leo III denied his approval and publicly posted the Creed in Rome without the Filioque, written in Greek and Latin on two silver plaques, in defense of the Orthodox Faith (810) stating his opposition to the addition of the {{lang|la|Filioque}} into the Creed.{{sfn|ODCC|2005|loc="Filioque"}}{{sfn|Siecienski|2010|pp=91–93}}{{sfn|Nichols|2010|pp=238–239}} Although Leo III did not disapprove the {{lang|la|Filioque}} doctrine, the Pope strongly believed the clause should not be included into the Creed.{{sfn|Maas|1909}}{{sfn|NAOCTC|2003}}{{sfn|ODCC|2005|loc="Filioque"}}{{efn|"Leo III defended the Filioque outside the Creed.}} In spite of the efforts of the Church of Rome, the acceptance of the Filioque clause in the Creed of the Frankish Church proved to be irreversible.

In 808 or 809 apparent controversy arose in Jerusalem between the Greek monks of one monastery and the Frankish Benedictine monks of another: the Greeks reproached the latter for, among other things, singing the creed with the {{lang|la|Filioque}} included.{{sfn|NAOCTC|2003}}{{sfn|Schmaus|1975}}{{sfn|Harnack|1898|loc=[http://www.ccel.org/ccel/harnack/dogma5.ii.ii.i.vi.iv.html ch. 6 §2]}} In response, the theology of the {{lang|la|Filioque}} was expressed in the 809 local [[Council of Aachen (809)]].{{sfn|NAOCTC|2003}}{{sfn|Harnack|1898|loc=[http://www.ccel.org/ccel/harnack/dogma5.ii.ii.i.vi.iv.html ch. 6 §2]}}{{sfn|Bray|1983|p=121}}