First Council of Nicaea (325)

This first Oecumenical Council is of the highest importance in the history of Christianity. Its convocation by Constantine shows the place which Christianity had become in the whole region and the confines of the Roman empire. And this within months of the conquest of the Eastern provinces, and primarily to deal with the Arian problem.  It should perhaps be noted that for Constantine his main interest was to maintain unity. And besides Bishop Hosius, it seems that Eustathius, Bishop of Antioch took some lead and authority. The two terms that came to the expression of most importance in the Nicene Creed were Homoousion (Gk. of one substance) to express the relations of the Son with the Father. And also perhaps the preferred term Homoiousion (Gk. of like substance with The Father), which was held to leave more room for the distinctions in the Godhead.

And later there was the longer formula, also known as the ‘Niceno-Constanopolitan Creed.’  It needs to be said, that the later Eucharist worship, and the added Filioque in the early Middle Ages, was not and never really accepted with the East and Orthodoxy. And many today in the Anglican Church, as in the Orthodox do not accept the filioque.