[Zigûr]

Originally Posted by Ivriniel

The refusal to accept that they were present during the Ainulindale, at which time, Melkor's disharmony and repetitious defiance were promulgated into Eru's orchestrations. Should it not have been entirely clear, before their music was made manifest in Arda in the Vision Illuvatar brought forth, that Melkor's presence was somehow significant.

A matter of faith, I suspect. The Valar must have accepted that Eru had a reason for permitting this to come to pass.

Originally Posted by Ivriniel

So, I'm presenting an alternative view to the reductionists' position and the categorical posturing of "Melkor is All Evil and That is Bad". Perhaps Evil serves Illuvatar's final purpose, in time to come, in ways the Valar are not far-seeing enough to discern.

I'm going to have to use the word "necessary" again because the way I see it the concept of Arda Healed is evil serving Eru's final purpose without evil being necessary: "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."
You may consider is reductionist, but the fact is that in Eä Melkor was the only source of evil, and all evil that followed was the influence of his spirit permeated through all matter. That being said, we do receive evidence of inexplicable sufferings, for example:

"among the Eldar, even in Aman, the desire for marriage was not always fulfilled. Love was not always returned; and more than one might desire one other for spouse. Concerning this, the only cause by which sorrow entered the bliss of Aman, the Valar were in doubt. Some held that it came from the marring of Arda, and from the Shadow under which the Eldar awoke; for thence only (they said) comes grief or disorder. Some held that it came of love itself, and of the freedom of each fëa, and was a mystery of the nature of the Children of Eru"

Originally Posted by Ivriniel

That's my first point: for example, avoiding the bringing of Arda to a terminal conclusion and endpoint is (arguably)--extending suffering

I think the issue is here that it wasn't the place of the Valar to decide the ultimate fate of Arda. That was for Eru only. They could have destroyed it, yes, but that would have been defiance of Eru's will. Destroying Arda would only perpetuate the evil of Melkor, not bring about Arda Healed. The destruction of Númenor is a perfect example, in fact. The Valar were not even willing to battle Men in that way, instead relinquishing authority to Eru. It was not their place.

Originally Posted by Ivriniel

(I mean, the Valar Combined had a great deal more power than Melkor)

I'm afraid this is contradicted in the text. Melkor was more powerful than all of the other Ainur combined. That was part of his nature: "he must not be able to be controlled or 'chained' by all the Valar combined." (Morgoth's Ring) Now of course Morgoth the person could be subdued. Melkor the Tyrant of Utumno, even, could be subdued. But that is not Melkor. Melkor is, to quote Professor Tolkien, "a tyrant (or central tyranny and will), + his agents." That's why the Valar cannot solve the problem of evil (although they did not need to - Eru had done it for them). Melkor was more powerful than all of them combined, and even when he was personally weakened his evil was still out there. No "eradication of Morgoth was possible, since this required the complete disintegration of the 'matter' of Arda."
Moreover "the dilemma of the Valar was this: Arda could only be liberated by a physical battle; but a probable result of such a battle was the irretrievable ruin of Arda." So evidently the Valar saw the latter as impermissible. Why? Because their function, and the function of Manwë in particular, was to "govern Arda and make it possible for the Children of Eru to live in it unmolested." They struggled in that role because of the power of Melkor. It was not in their power or authority to destroy Arda and thus make it impossible for the Children to exist, which was the only other means besides "Arda Healed" of stopping Melkor, but not considered to be a valid alternative.

I think the issue might be that you take a somewhat different view of good and evil than that taken by Professor Tolkien and that which is reflected in his texts, because I think your theory only really works if good and evil operate in a somewhat different way than they actually do in Eä. This may or may not be the "true" way they operate in the real world (if it's even meaningful to say so - metaphysics is, arguably, a somewhat outdated discipline in the "real world," as meaningful as it clearly is in Arda) but this is how good and evil operate in Eä and it probably also reflects how Professor Tolkien considered them to operate himself (albeit according to his real-world beliefs, obviously).

Anyone else should feel free to chip in their thoughts here, of course. I fear I'm rambling on excessively, but hopefully this discussion is setting minds in motion regarding a very interesting issue of Professor Tolkien's late writings. Perhaps his philosophical musings did get in the way of him completing The Silmarillion, but that was probably impossible anyway so I'm glad we've got what we've got.