Is this thread still about reformed type doctrine or has it become something else?
Given that reformed doctrines form an entire worldview/belief-system in itself, I suppose pretty much everything we discuss would have to be explained by these. And since the doctrine of freewill is a distinctive point of difference too, I see we're pretty much on track discussing that.
Just to set some clarity again, when I deny freewill, it's not that I'm denying man his will itself. Of course, man has the ability to will - it's just not free to operate by itself, apart from the influences of sin in his flesh or of God in his spirit.
Adam and Eve did not have a corrupted, sinful nature (depraved mind) when they were created. Neither were they created spiritually dead.
And yet they could disobey God and they sinned. How and why were they able to do that?
While they were not created spiritually dead, they were not operating in the spirit either - man was first created in the flesh, with God's plan to rebirth him in the spirit after the fall by redemption in Christ - the natural comes first, then the spiritual(1Cor 15:46).
In that, I believe -
1. Adam and Eve had what we refer to as freewill in the flesh - in the sense that their flesh was not yet corrupted by Sin and they could make choices according to their Self and they were held responsible for the choices made by their Self(flesh-nature).
Also note the sequence of Eve's deception -
a) Eve had knowledge of the truth (Gen 3:2-3)
b) the serpent draws attention to God's commandment, probably emphasizing the "every/any tree" to instigate thought on why it wasn't uniform all across (Gen 3:1).
c) the serpent presents the lie (Gen 3:4). But Eve already had the truth, and this lie cannot replace it until that truth is corrupted.
d) the serpent mixes a lot of truth about how their eyes will be opened(Gen 3:7), how they shall be as gods knowing good and evil(Gen 3:22) with the deceptive corruption in the phrase "
For God knows these will happen" - as if to suggestively imply that God, out of His own insecurity or vain desire to be pre-eminent, commanded them against eating of that tree(Gen 3:5).
e) Eve, in the flesh, couldn't resist the deception because the flesh/Self-nature was fed a reason that it relates to - and thus the truth was replaced by the lie, thereby removing the constraint of death in eating the fruit. But we act simply not out of the absence of negative constraints, but require the presence of positive impulses too.
f) And there were many positives to lust over - The tree was good for food(Gen 2:9), it was pleasant to the eyes(Gen 2:9) and it was desirable to become wise(Gen 2:9 - tree of knowledge) - and in that, she had the lust of the flesh, the lust of the eyes and the pride of life (1John 2:16). These lusts are of the flesh, and weren't aroused as long as it was restrained by the truth - but once the truth was corrupted with the lie, these lusts brought forth sin and consequently death(James 1:15).
g) Adam, though not deceived in the like manner of Eve, was blinded to the truth in the very knowledge of Eve having eaten the fruit. While Eve was corrupted into believing a lie, Adam was corrupted into rebelling against the truth - and in that, we see Sin's(deceiving nature of rebellion) overcoming them into bondage.
2. Therefore, the flesh is weak in itself to resist corruption - and to consequently stop lusting and sinning. This in essence depicts the overcoming of the flesh by Sin itself and bringing it into bondage(2Pet 2:19) - in order to cause it to make the choices that are against God. I don't believe Adam or Eve chose freely to disobey and in that, permit Corruption in them - I believe Corruption overwhelmed the flesh into bondage and consequently they disobeyed.
And this must necessarily be true for God to be Just, lest we question God's fairness in the doctrine of Original Sin, where each of us begin questioning why God didn't allow each of us to make our own free-willed choice in the Garden scenario instead of concluding us under sinful flesh by default. This objection is shut when man is shown the inevitable failure of the freewilled flesh against Corruption, and that each of us would face the very same verdict in the exact same way, thereby making Adam our federal representative.
As to Why this must be so - as discussed earlier, God reveals His wondrous plans,purposes and gives us knowledge of His Holy attributes and leads us to obedience through faith in love - by contrasting the failure of our Self/flesh against the life in the spirit which He Himself works in.