Holy Spirit in Christianity

===Procession of the Holy Spirit===
{{Main article|History of the Filioque controversy|Eastern Orthodox teachings regarding the Filioque}}
In John 15:26, Jesus says of the Holy Spirit: "But when the Helper comes, whom I will send to you from the Father, the Spirit of truth, who proceeds from the Father, he will bear witness about me."<ref>{{bibleverse||John|15:26}}</ref> In 325, the [[First Council of Nicaea]], being the first ecumenical council, ended its [[Nicene Creed|Creed]] with the words "and in the Holy Spirit". In 381, the [[First Council of Constantinople]], being the second ecumenical council, expanded the Creed and stated that Holy Spirit "proceeds from the Father" (ἐκ τοῦ Πατρὸς ἐκπορευόμενον). This phrase was based on John 15:26 (ὃ παρὰ τοῦ πατρὸς ἐκπορεύεται). In 451, the [[Council of Chalcedon]], being the fourth ecumenical council, affirmed the [[Nicene-Constantinopolitan Creed]].{{sfn|Meyendorff|1989|pp=}} During the same time, the question of procession of the Holy Spirit was addressed by various Christian theologians, expressing diverse views and using different terminology, thus initiating the debate that became focused on the [[Filioque|''Filioqu''e]] clause.

In 589, the [[Third Council of Toledo]] in its third canon officially accepted the doctrine of the procession of the Holy Spirit from the Father and the Son (''a Patre et Filio procedere'').{{sfn|Martínez-Díez|Rodriguez|1992|p=79}} During the next few centuries, two distinctive schools of thought were gradually shaped, Eastern and Western. Eastern theologians were teaching that the Holy Spirit proceeds from the Father only (notion referred as ''monoprocessionism''),{{sfn|Wilhite|2009||pp=285–302}} while Western theologians were teaching that the Holy Spirit proceeds from the Father and the Son (notion referred as ''filioquism'').{{sfn|Phillips|1995||pp=60}} Debates and controversies between the two sides became a significant point of difference within Christian [[pneumatology]], including their historical role in setting the stage for the [[East–West Schism|Great Schism of 1054]].