In the canon and even much conventional theology, it's not clear, and not even clear that Satan is a moral agent capable of doing good or evil. Plus, he doesn't show up much in the canon; there's the bet with God over Job, the test/temptation of Christ, some stuff in Revelation, and the fact that the snake in the Garden of Eden is popularly (though not canonically) identified with Satan.
Milton's work is an artistic take on a popular old non-canonical story that both is influential on shaping images of Satan in Christianity and hard to reconcile some mainstream theology (Christian theology and Christian popular mythology often have a problematic relationship.)
> not even clear that Satan is a moral agent capable of doing good or evil
This was what got me - as I understand it, the special thing about humans was free will, which kind of emancipates any of the Heavenly Host from wrongdoing (at least in the sense of personal moral responsibility).
If on a spectrum of God <--> !God, humans were supposed to turn their interest toward god. But, rather than having God and Void apposed, there is a personified force there that is "the adversary".
Almost like a divine unit testing framework: if there are critical weaknesses, please help me uncover them ASAP. Hence God's willingness to let Satan make Job's life miserable.
Acceptance testing, surely.
Essentially, his hubris in seeking to overcome the nature of things. While Satan's sin, in the personified tale of the story, boils down to not doing what god says, "going against the will of god" essentially means being foolish enough to think you can live out of harmony with the natural order of the universe just because you're intelligent and have the desire.
The entire god/adam/eve/satan/christ narrative is essentially a parable to illustrate how the wise, to live calm, harmonious, fulfilling lives, live acording to the Dao, as some in the East would say.
Killing a buffalo to feed and clothe yourself isn't evil, but slaughtering an entire herd to sell the horn powder to Eastern mystics might be. And you'll be punished by suddenly having no buffalo to eat.
Not the greatest example though. :P
"Wherefore, because that Satan rebelled against me, and sought to destroy the agency of man, which I, the Lord God, had given him, and also, that I should give unto him mine own power; by the power of mine Only Begotten, I caused that he should be cast down;" (Moses 4:3) [emphasis mine]
"And thus he goeth up and down, to and fro in the earth, seeking to destroy the souls of men." (D&C 10:27)
At least, that's one take.
It’s been a couple months since I read Paradise Lost though.
Are we talking about the bible or Milton? I agree it's not clear in the bible, but feel Milton makes it quite clear.
It might have been harmful to humanity to have been kicked out of the garden
I'm not even really sure that's the point. 'Humanity' is a third party in that fight. God had built this new, fragile creature, the 'best' thing he'd ever made. He realized they where fragile and put them in the garden to protect them. Satan is pissed off at God for casting him out and decided to fuck with God by breaking his new toy that he knows God is very proud of. None of them seem to care too much about the long term fate of humanity.
If a child destroys a poorly-built house by kicking it, do we blame the child?
If a child destroys an extremely fragile work of art, do we blame the artist for not making his art more robust.