This question already has an answer here:
I've seen lots of exploration and answers to the nature of free will and how this gives rise to the possibility of choosing evil because choosing good is meaningless if it's the only choice to make. But this leaves me with questions, one in particular that I'll ask after some brief explanation, followed by the best answer I can muster:
I understand that Adam and Eve were made wholly good, but naive to the knowledge of good and evil so it's understandable that Lucifer/Satan could trick them fairly easily as he did. Lucifer was also created wholly good, and it seems unlikely that a being with the knowledge of good and evil would choose not to be wholly good as that's not a wholly good thing to do, it's a bad thing to do.
Question: How is it possible that a wholly good being, which by definition would never choose evil, chose evil? It seems like a logical contradiction, I just can't get my head around that without invoking the non-answer of "it's a mystery".
If angels don't suffer like humans do, i.e. if pain and emotional torment aren't a thing for them then it's entirely possible that they might make their choices in a different way, i.e. there are no safeguards to keep them from choosing evil. By contrast humans can suffer, but until we experience pain first hand we don't learn to fear it and so I can see how God would use evil to teach us so that when he makes us wholly good again we'll know and fear choosing evil, so we'll still have meaningful free will but we won't choose evil despite it being a choice. (I will call this "free-bias").
Because God can't create evil beings he'd have to have some way to introduce evil to wholly good beings with complete free will to teach them and introduce a bias to them that they choose for themselves due to experience, had he just created the angels with a free will that was already biased then that bias wouldn't be their choice and so they'd have an incomplete free will - God doesn't create beings like this, he doesn't need slaves. (I will call this innate-bias).
The raises more questions, but I don't expect answers to these, I'm only mentioning them to share them in context: Wouldn't this mean that God basically knowingly made beings (angels) that would sacrifice themselves to achieve what God could never do otherwise without creating evil himself? And if so is it fair? Is fairness dependent on the nature of the being perhaps rather than being an absolute for all beings?
God be with you!