*The heresies of [[Macedonianism]] and [[Apollinarianism]], off-shoots of the [[Arianism|Arrian heresy]]

*Expanding and adapting the [[Nicene Creed]], in particular, developing the teaching upon the [[Holy Spirit]]

Regarding the teaching of the Holy Spirit, the Council affirmed him to be God "even as the Father and Son are God: who proceeds from the Father, who with the Father and the Son together is worshipped and together glorified." After about 381, [[Arianism]] ceased to be a relevant issue, save for a few remote parts of the empire.