[OBW]

I note that virtually everything else in creation changed as a result of the Fall. Thorns; thistles; animal kills and eats animal; man eats by the sweat of his brow. Did Satan do this? Actually, I believe the Word says God did.

How did the change in man occur? Other than the obvious fact of the loss of fellowship with God, KSA is right to say that "I do not know." I don't think that was made known to us. The cause and result are mentioned throughout scripture, but the mechanics/physics/biology of the actual change is not. It is quite possible that the removal of the active presence of and fellowship with God gave license to man's free will to do according to his own considerations. That is not to say that God was restraining man before, but that the every-present experience of Him was a guide of choice for man. (That would even be consistent with the post-regeneration aspect of walking according to the Spirit to fulfill God's righteousness. It might be argued that while still quite choosable, an aspect of the pre-fall condition is restored upon our regeneration.)

It would appear from previous threads on this line that it is not even clearly stated all that was before the Fall. We know there was this situation of peace and fellowship with God. There was peace within the setting of the garden whose name, Eden, is now associated with utopia. But there is uncertainty as to exactly what man's position was with respect to God beyond what is written in the short history of creation up to the Fall. That makes the analysis of the change even more speculative.

And while having some external thing — a little bit of Satan — injected into man is not clearly in opposition to scriptures, all of the relevant scriptures can be understood without such fact being assumed (in my opinion).