We had a nice discussion on the origin, nature, and end of evil today (Declamation in Lordship), and I have come to slightly modify my view.
The end of evil is nothingness, which I have held for a long time. The nature of evil is always progressing towards its end, the only variation being the rate: amble downhill or swan dive off a cliff?
The origin is somewhat new. I hadn't considered it until I hit the later portions of City of God, in which Augustin(e) discusses it to some rather considerable length. He was still obfuscating "round about a meaning" a hundred pages after my attention span had begun dwelling upon exactly what our carpet might taste like (rather dry; needs vacuuming).
It's somewhat of a chicken or the egg quandary, so let me try out a few axioms, a la Euclid, though it will probably work as well as a la Descartes: "cogito, ergo sum. Cogito? Cogito cogito, ergo...um...ergo cogito? Ita. Cogito, ergo cogito. Cogito. Cogito? Sed..." This is why Descartes started using heroin.
1). God freely and unalterably ordained whatsoever comes to pass.
2). Evil came to pass.
3). "aardvark" is one of the great words of the English language.
4). Creation was "all very good".
And here is one that I would propose, but may or may not fly with all of you. If you can disprove it, I'll think of something amusing to do when I feel like it.
5). All that exists is for the glory of God.
So, we know that God is responsible for evil, and we know that He is not the author of it.
We also know that it came to pass sometime between the initial creatio ex nihilo of Genesis 1:2 and the 2nd chapter of Genesis.
If we accept axim #5, and we go by Isaiah 14, then this is what we can say so far as Satan is concerned: He was created to glorify the infinite God, and chose, in the perfect plan and will of God, to glorify his finite self.
The chicken or the egg (obviously the chicken) is here: God created Satan, and all of God's creation was all very good. Evil comes from evil desires (namely pride), but where do the evil desires come from? A shift of focus from God to self. Is that not evil in itself? Then where did it come from? Evil desires. And so on and on it goes. At this point, I'd like to mention that my brain is full, and Satan sinned, so tace, and we'll move on.
The movement of evil from infinite good to the absolute negation that it ends up with is not surprising, considering what the first movement of evil is: a decision to glorify the finite self over the infinite God.
This is all I feel like writing at the moment; interesting things to dwell upon are the distinctions between different types of evil: "natural" disasters, evil objects, evil actions, and evil desires.