[Erestor]

Originally Posted by Nikkolas

The most interesting and telling quote for me in the entire Silmarillion is whn Eru addressed the Ainur and Melkor specifically:
"And thou, Melkor, shalt see that no theme may be played that hath not its uttermost source in me, nor can any alter the music in my despite. For he that attempteth this shall prove but mine instrument in the devising of things more wonderful, which he himself hath not imagined.’

I've often wondered if Morgoth or Sauron remembered or forgot this. The fact is, all the evil committed by either Melkor or Sauron through all the Ages was just part of Eru's Plan.

Morgoth at least possibly either forgot or dismissed it because his pride was boundless. For Sauron though, maybe he did remember and even dared to think what he was doing was "right" as it was permitted by Eru.

I don’t think that Sauron would've used that knowledge in such a way. After all, he thought Eru had left Arda, and that’s why he didn’t fear his intervention. If he deluded himself to think he was doing the right thing, he wouldn’t need to fear Eru, or think that way. Also, he inherited at least some of Morgoth's hatred of Eru (according to Morgoth's Ring). I rather think he would distance himself from such views. Even when he acted like an emissary from the Valar in Eregion to help the Elves to forge the Rings, he wouldn't do it in such ways, but would really appear as a good being.

I think that view would be more like Gandalf’s, if he would become Ring-Lord. From Letter 246.

Gandalf as Ring-Lord would have been far worse than Sauron. He would have remained 'righteous', but self-righteous. He would have continued to rule and order things for 'good', and the benefit of his subjects according to his wisdom (which was and would have remained great).
The draft ends here. In the margin Tolkien wrote: 'Thus while Sauron multiplied [illegible word] evil, he left "good" clearly distinguishable from it. Gandalf would have made good detestable and seem evil.'

That is, if he still had all his knowledge from before his embodiment. I’ve always wondered about this certain passage from UT, which gives me the impression they had lost part of their knowledge.

For it is said indeed that being embodied the Istari had needs to learn much anew by slow experience, and though they knew whence they came the memory of the Blessed Realm was to them a vision from afar off, for which (so long as they remained true to their mission) they yearned exceedingly. Thus by enduring of free will the pangs of exile and the deceits of Sauron they might redress the evils of that time.