Following this strand of the thread through--
The right word is not change but mutability. Immutability "lite" being:
The Immutability of God is an attribute where “God is unchanging in his character, will, and covenant promises." [1]
The Westminster Shorter Catechism says, ’God is a spirit, whose being, wisdom power, holiness, justice, goodness, and truth are infinite, eternal, and unchangeable.” Those things do not change. A number of Scriptures attest to this idea (e.g. Num. 23:19; 1 Sam. 15:29; Ps. 102:26; Mal. 3:6; 2 Tim. 2:13; Heb. 6:17–18; Jam. 1:17) [2]
God's immutability defines all his other attributes: he is immutably wise, he cannot but be merciful, good, and gracious. The same may be said about his knowledge: God does not need to gain knowledge; he knows all things, eternally and immutably so. Infiniteness and immutability in God are mutually supportive and imply each other. An infinite and changing God is inconceivable; indeed it is a contradiction in definition. [3]
So I think you, Jerry, would affirm that in the Word (God) becoming man, nothing changed regarding "His character, will, and covenant promises" simply with the addition of flesh. And so would most of us.
Then there is metaphysical immutability which is closer to "Infiniteness and immutability in God are mutually supportive and imply each other. An infinite and changing God is inconceivable; indeed it is a contradiction in definition" but saying more as a consequence of God's simplicity:
In Christian theism (to be accurate "Classical theism"), God is simple, not composite, not made up of thing upon thing. Thomas Morris notes that divine simplicity can mean any or all of three different claims:
God has no spatial parts (spatial simplicity).
God has no temporal parts (temporal simplicity).
God is without the sort of metaphysical complexity where God would have different parts which are distinct from himself (property simplicity).
In other words, property simplicity (or metaphysical simplicity) states that the characteristics of God are not parts of God that together make up God. Because God is simple, God is those characteristics; for example, God does not have goodness, but simply is goodness
So (whether you agree or not), you are engaged in metaphysics. The nature of God, His identity, angels, souls, spirits, man, flesh, body, causation, etc., are all in the realm of metaphysics. No one can avoid metaphysics and metaphysical assumptions when speaking of God. The only question is whether one does it well (coherence--and in our case alignment with the Biblical data) or badly.
So what some of us are here saying is that the Word is divine (has the divine nature) and is immutable. Strictly speaking, and metaphysically, it was the Word who became flesh (not Jesus Christ per se though we can certainly say
of the Word that He is Jesus Christ).
And rather than saying divinity or deity changed, we say creation changed--creation also being His flesh/humanity which wouldn't have existed but for Him.
Creation entered into a new relationship with its Creator. Flesh pops into and out of existence all the time--and none of that changes the Creator to include His
own flesh. So some of us argue even this stronger version of immutability.
Finally, and back to Arsenios' train of thought, even if one cannot accept that there was no metaphysical change, certainly (I hope) you would agree that there is no experience that God is unaware of. He didn't need to become man to experience what it is like to be man--He already knows and
precisely. Not only, He knows what it is like precisely to be
this or
that man. He knows
everything. And knowing that results in no change in Him. So an instantiation/actualization/realization of that knowledge in creation doesn't change Him either. It was done to show us something always and eternally true. And some of us argue this version of immutability as well (and I think you might too).
So we only disagree (at this point) on 1 of the 3 examples of immutability--the metaphysical one.
It helps to think of God as the stable point from which everything
else revolves around. Everything is in relation to Him, and He is the same whether or not we (or the entirety of creation itself) exists.
The relation is asymmetric (unsurprisingly). Our relationship to Him is an internal relation for us. His relation to us is an external relation for Him.
Okay, I'll shut up as I think I'm rambling now...