The Inherent Incompatability of Morgoth and Sauron

[Zigûr]

Originally Posted by Sarumian

I wonder what Sauron could think about the Music. I don't believe he could ever forget it as it must have made the most profound impression on his soul ever. Thus, Melkor needed to work hard to persuade Sauron that his (Melkor's) plan can bore a fruit. It is also very difficult to accept that Sauron could believe that Eru literarily abandoned Ea: Eru's nature doesn't simply allow him to abandon anything that does exist. Either Sauron had a very faulty idea of Eru or he believed that taking responsibility for Middle Earth is The Way - something that Eru would approve or at list tolerate. At least during his brief repentance, if it was a sincere move.

"He probably deluded himself with the notion that the Valar (including Melkor) having failed, Eru had simply abandoned Eä, or at any rate Arda, and would not concern himself with it any more." (emphasis mine)
Sauron's impression of Eru was not based on rational thought. Rather, in his corruption, he had (so far as I read it) concocted a false understanding of Eru's mind which conveniently permitted his own schemes.
"...Sauron was also wiser than Melkor-Morgoth. Sauron was not a beginner of discord; and he probably knew more of the 'Music' than did Melkor, whose mind had always been filled with his own plans and devices, and gave little attention to other things."
"Though one of the minor spirits created before the world, he knew Eru, according to his measure."
So while Sauron participated in the Music and was aware of Eru, we must focus on that phrase: "according to his measure." Sauron was mighty among the Maiar, but not that mighty in the grand scheme. I would argue that his understanding of Eru, and of the Music, was limited (but at the same time greater than his master's). I restate again Gandalf's remark that Sauron judged all things "according to his wisdom" and from Morgoth's Ring the observation: "His cynicism, which (sincerely) regarded the Motives of Manwë as precisely the same as his own, seemed fully justified in Saruman."
Sauron probably did not see himself as "corrupt" or "evil" because he inevitably scrutinised others as if they had the same personality as himself; he saw himself as the norm. I believe this is how he could convince himself that Eru had abandoned Arda.
Did Morgoth need to "work hard to persuade Sauron"? I see no evidence of it personally. Quite the reverse, in fact. If you were as single-minded as Sauron seemingly was I think it would seem entirely rational to side with the most powerful party. He may not have understood the Music well enough to comprehend the futility of supporting Morgoth, even if he understood the Music better than Morgoth did himself. Perhaps the Music itself in its complexity contributed significantly to Sauron's obsession with order and how everything might be weaved into a single, perfect pattern. I read Sauron's greatest weakness as his perfectionism.