[Mithadan]

Coming into this thread late. Other than perhaps Morgoth himself, Tolkien did not believe that anything with a mind was "irredeemably evil" (his phrase, not mine and not the same as "inherent"). This led him to struggle with the nature of Orcs, Trolls, and to a lesser extent dragons. I seem to recall that he reasoned that these corrupted or constructed beings could not solely be tools of the will of Morgoth and Sauron or else they would be inanimate when their masters' attention was elsewhere and would not have even the slight self-interest shown by Gorbag and Shagrat. So while he toyed with the idea that Orcs might simply be animals, perhaps apes, that were corrupted, he settled upon them being one of the sentient races in the end (though he wavered between Men and Elves as the source of Orcs and never explained the origin of Trolls).

Dragons appear to fall into a different category. The earliest conception of dragons is in Lost Tales, where they are stated as being "made" by Morgoth and having "great cunning and wisdom." However, Tolkien later reached the conclusion that Morgoth was incapable of creating any thinking entity. I suggest that dragons were bred from lesser reptiles in a fashion similar to how Carcharoth was bred and "inhabited" by "spirits" that animated them. In Morgoth's Ring, Tolkien discusses certain great Orc captains such as Boldog and states that they were inhabited by spirits of some power.

If we accept this premise, dragons are evil from the beginning because the spirits that inhabited them were evil. However, Tolkien would likely not say they were "irredeemably evil." In Letters JRRT says that even Sauron was not irredeemably evil in that he at one time served another, Aule. This creates at least the possibility of a "reformed" dragon, though public reaction might be the same as the Troll mentioned in the last post by Faramir Jones.