The Inherent Incompatability of Morgoth and Sauron

[Boromir88]

To go along with what Zigur brings up with how Sauron originally was drawn Melkor's rebellion because he was you could say, star struck, but Melkor's splendor and ability to implement his designs relatively quickly.

He [Sauron] still had the relics of positive purposes, that descended from the good of the nature in which he began: it had been his virtue (and therefore also the cause of his fall, and of his relapse) that he loved order and co- ordination, and disliked all confusion and wasteful friction. (It was the apparent will and power of Melkor to effect his designs quickly and masterfully that had first attracted Sauron to him.)~Home X: Morgoth's Ring; Myths Transformed

Later, Morgoth spun downwards into nihilism, and Sauron never reached this stage of chaos, since he still had, what Tolkien calls "relics of positive purposes." I think, given enough time Sauron was following down the same path and would have become a nihilist:

In all the deeds of Melkor the Morgoth upon Arda, in his vast works and in the deceits of his cunning, Sauron had a part, and was only less evil than his master in that for long he served another and not himself. But in after years he rose like a shadow of Morgoth and a ghost of his malice, and walked behind him on the same ruinous path down into the Void.~The Silmarillion: The Valaquenta

I like how you break it down between Chaotic Evil and Lawful Evil. It sounds like two apt descriptions.

[Inziladun]

To me, the sin of Morgoth and Sauron is practically identical: each believed his version of "order" to be superior to that established By Ilúvatar through his servants, the Valar. Though Melkor merits a greater penalty for being the prime corrupter of the efforts of the Valar, Sauron's telling error was his inability/unwillingness to humble himself after the fall of Morgoth. That should have been a red flag to him that his road was a dangerous one that would lead him to ruin. Pride in the memory of his power under Morgoth filled him though, and pride led him to think he could order the world to his will despite his much greater master being proven incorrect on the same assumption.
It is my belief that anyone can make a mistake, and I don't fault Sauron so much for his initially following Morgoth. What I do criticize him for is his failure to repent when given the chance. Saruman's later fall is a result of the same arrogance and lack of humility.

Originally Posted by Boromir88

Later, Morgoth spun downwards into nihilism, and Sauron never reached this stage of chaos, since he still had, what Tolkien calls "relics of positive purposes." I think, given enough time Sauron was following down the same path and would have become a nihilist

I think Third Age Sauron was at the nihilistic point. Whatever had originally guided him to try and make the world his own he had lost sight of, blinded by the prospect of simply having power and control. A world of Orcs and evil men was not his ideal: he preferred to enslave the West. It was not then enough that lesser beings did his will. They should be made to do it against their own.

[mhagain]

I'm inclined to view Sauron as being more Lawful Neutral than Lawful Evil, at least at the start, and not in the Moorcock/Balance sense but rather in the "I'm looking after my own skin here" sense.

It's definitely the case that he was quite content to sit out the end of the First Age as a boogeyman in Taur-nu-Fuin after Luthien whupped his ***, and his repentance after the War of Wrath indicates that he was prepared to switch sides according to what suited his purpose.

It's really only after the Rings were created that he went fully down the Evil path, IMO. Up until then he's more of a free agent who just happened to side with Melkor because that seemed to be where the smart money was (at least from the perspective of him meeting his goals for order/etc).

[Andsigil]

It's misguided to shoehorn Sauron and Morgoth into alignments from a roleplaying game and declare them compatible or not.

People of different temperaments have followed each other loyally through all ages of history.