[aruanan]

Why this and not some lone human disobedience to God was the prototype of all sin, I think there has to be a reason.

Well, it was the prototype because it was the first example (in Adam, not Eve) of willful disobedience. Eve was fooled. Adam was not. She was alone and got snookered. He came back and she offered it to him and he chose to go with her rather than his previous instructions from God. But everything that Eve had experienced from the serpent is exactly what James describes as arising within a person's own self:

When you are tempted, you shouldn't say, "God is tempting me." God can't be tempted by evil. And he doesn't tempt anyone. But your own evil longings tempt you. They lead you on and drag you away. When they are allowed to grow, they give birth to sin. When sin has grown up, it gives birth to death.

The popular idea that sin happens as a result of Satan or one of his demons coming and whispering in one's ear is the same sort of myth as that which posits God as the ruler of heaven and Satan as the ruler of hell; the angels and demons fighting over one's soul, one whispering in one ear, the other whispering a contrary message in the other, trying the pull the person one way or the other (the funniest example seen in South Park Episode, Ike's WeeWee, when Mr. Mackie gets tempted to drink after getting fired for losing control of a lid of Columbian red). It's popular imagery that's more Zoroastrian in origin than Christian.

[HiTech RedNeck]

You cannot reason from “God cannot tempt” scripture to “the devil has no hand in some sin.” I believe there is scriptural evidence that the devil does have a hand in all human sin, whether through past chains of events or actively in the present. The devil certainly is there cheering at all human sin, if nothing more. The fear of the Lord is “to hate all evil” and you have to have a coherent view of evil in order to be able to coherently hate it without hating what is righteous as well.