The Chalcedonian Definition describes Jesus as homoousios with mankind with respect to his humanity:

“He is of the same essence (homousios) as the Father according to his deity, and the same one is of the same essence (homousios) with us according to his humanity, like us in all things except sin.”

In some sense Mormonism teaches that the Father and Son are homoousios, and that humanity is homoousios with all the exalted gods.

Thus the chasm between Mormonism and Christianity is more about the ousia of deity itself than whether the Father and Son are homoousios. It posits a potentially infinite number of beings and infinite particles of matter that God did not (and even cannot) create. Hence, Mormonism substantially (even if not superficially) rejects the very first line of the Nicene Creed:

“I believe in one God, the Father almighty, maker of heaven and earth, of all things visible and invisible.”

This is more fundamental than its superficial rejection of homoousios. Regarding that term Ron Huggins says,

“Mormons delight in targeting this word homoousios in the creed as making a serious departure from the Bible into the realm of philosophical speculation. I have never read a Mormon writer who notices that homoousios echoes the earlier use of ousia… Or that the introduction of both words can be seen to represent a fairly modest clarification, namely that Jesus was the Son, not the creature of the Father. An idea, by the way, that Mormons agree with.

“Indeed, I sometimes wonder why Mormons, in the midst of attacking the word, have never paused long enough to notice that their own doctrine might be able to apply homoousios in a much more comprehensive way, by using it to describe how all humans are of the same species as God.

“Mormons regularly say that we’re all of the same species as God. Why not simply take homoousios to refer to that in the context of plurality? Were they to do so, it might actually bring more clarity to Christian-Mormon discussion by setting out in sharper relief the difference between the biblical and the Mormon meaning of the term ‘only-begotten’.” (“Those Abominable Creeds”, by Ron Huggins, 25:44)

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Added December 10, 2025

Caveat to watch out for: Christians affirm that the Father and Son are homoousios in a different manner (as God, per divine simplicity) than creatures can be of the same species.