[greyhavener]

It seems to me that both Gandalf and Galadriel rejected the opportunity to possess the ring that would have made them become evil. Although neither was inherently evil, each recognized his or her own potential for it..

Saruman started out as the White, certainly not evil. He did not consciously choose to become evil but evil he became due to his association with evil and his belief in his own power to overcome it.

The ring itself presented Isildur, the Nine, Gollum, Bilbo, and Frodo with the same opportunity. It is not labelled "evil", but rather deceived by presenting itself as something that would satisfy a desire each had. To Isildur and the Nine it whispered "power" and to Gollum, Bilbo, and Frodo it enticed with a promise of safety and the specialness one feels by possessing something "precious."

Melkor always had the option of altering his music. He chose not to.

This sort of discussion always leads to the philosophical question of the ages: If the origin of all things is inherently Good, can good be the first cause of evil?

It is my opinion (and reasonable minds certainly disagree) that only within the realms of will or choice rather than a predestination or fate can the Good remain inherently Good. I don't think creating a potential is the same as creating an intent.