Who was Jesus? For the Christian, Jesus was the Christ, the anointed one, predicted since ancient times by Jewish wise men. He had come to earth to lead all men to God. He was the son that made God a father. A father and a son. But what did that mean for God?
Christian books split on the question.
“Believe above all that there is one God, who created and fashioned all things, and making them to be out of that which is not”, said one Christian book. “The Father is greater than I”, another quotes Jesus. “From the womb before the morning star have I begotten Thee”, sang an old Jewish song to predict him. “For God so loved the world, that he gave his only begotten Son”, he said of himself. God made all including his son. He was created first but he was a creature. But Jesus said, “I and the Father are one”, “I am in the Father and the Father in me”. “No man knows the Son but the Father, and no man knows the Father but the Son.” The father and son are one, truly known only to each other. The son is no creature. He is utterly different, at one with God, of a majesty beyond our conception.
Leaving the Church split. Her leaders had to meet, all of them, and agree. The Council of Nicea was summoned.
One creed had to be made and one word began to circulate. “Ousia”. Translated as “Substance” by the few Latin’s present. A word of the Philosophers, one Latin had wrestled with before. Did they capture the Greek? No inspired book had it, but Ousia would clarify the truth they all revealed. Father and son, “of the same substance”, “homoousian”. The Eusebians tried for “of similar substance”, “homoiousian”. An “I”, one iota, separated the words. “‘Similar’. That’s meaningless”. “The same, the same”, became a chant. Only it was in accordance with true religion.
And there it was. Father and son were “of the same substance”, “Homoousian”. That missing “i”, that
most important diphthong made the son the equal of the father and not a creature. God inspired the majority at Nicea to this conclusion and they enshrined it in the Nicean (Nicene) creed.
Today, few Christians acknowledge  the significance of Nicea, saying that it merely affirmed the obvious     with protestants, if they address it at all, adding that its conclusions are clear from the clearcut bible  . Like other great fourth century cities, Nicea gets few   visitors. Attest to its significance and you have a faith defined centuries after its founder and contradictory books in great need of official dogma. Best leave those alone.