Of one being (homoousios)

Of one being with the Father

Homoousios joins two Greek words: homos, ‘same’, and ousia, ‘being’ or ‘essence’. The Nicene Creed confesses the Son as "of one substance with the Father" Nicene Creed, and many modern translations say ‘of one being’. Either way the claim is the same. The Son is not the highest thing God made, nor a second god resembling the first, but true God, sharing the one divine essence of the Father.

The word is not in the Bible, but it guards what the Bible says about the Son:

In the beginning was the Word, and the Word was with God, and the Word was God.

John 1:1

When Jesus called God his own Father, his hearers understood him to be "making Himself equal with God" (John 5:18). He also said, "I and the Father are one" (John 10:30). Some read that as no more than a unity of will. Hilary of Poitiers answered them: "This unity, not creation but nativity, not will but power, not unanimity but nature accomplishes" Hilary.

From Nicaea to Chalcedon

Early in the fourth century Arius, a presbyter of Alexandria, taught that the Son was the first and greatest of God's creatures (see Arianism). According to Athanasius's later account, the bishops at Nicaea in 325 first tried to confess the faith in biblical phrases alone, but Arius's supporters accepted each phrase and read it in their own sense. So the council chose a word they could not reinterpret: homoousios. The creed as completed at Constantinople in 381 confesses the Son as

God of God, Light of Light, very God of very God; begotten, not made, being of one substance with the Father, by whom all things were made.

Nicene Creed

The word was not welcomed at once. Some objected that it was not in Scripture; others feared it blurred Father and Son into one person, as modalism did. Councils in 359 settled for saying only that the Son is ‘like’ the Father, and another party proposed homoiousios, ‘of similar being’. The difference was a single letter, but similar is not the same. Through the long labours of Athanasius and the Cappadocian Fathers the Nicene faith prevailed, and the Council of Constantinople in 381 reaffirmed it. Later confessions use the same word of the Spirit: the three persons are of one substance.

The Council of Chalcedon in 451 used the word twice over of Christ, confessing him "consubstantial with the Father according to the Godhead, and consubstantial with us according to the Manhood" Definition of Chalcedon. The one who saves us is truly God and truly one of us. The Orthodox, Catholic and most Protestant churches hold this confession together. The story is told more fully in the lesson Nicaea: is the Son truly God?