[Raynor]

Originally Posted by davem

There's no evidence that Saruman wanted to become evil

Well, if we define evil as you did:

'Evil' is not a thing in itself but a corruption of good, where self aggrandisement, lust for power & contempt for other wills dominates

then there is plenty of evidence that he wanted to become evil.

he was corrupted by the belief that the end justifies the means

I don't think that "corrupted" is the most adequate term. There was no compelling force acting upon him. He chose this path consciously and freely.

Gandalf would not 'choose evil' because evil is not a plain & simple thing which is easily identifiable.

I disagree; omniscience is not required in order to stay on the moral path:

Originally Posted by Note to Melkor/Morgoth, Myths Transformed, HoME X

Every finite creature must have some weakness: that is some inadequacy to deal with some situations. It is not sinful when not willed, and when the creature does his best (even if it is not what should be done) as he sees it - with the conscious intent of serving Eru.

Gandalf would choose, as I said, to cut corners, over-rule others, focus on the end rather than the means.

But these are certainly evil acts, in breach of the mission he received.

Did Saruman actually consider himself evil?
...
Gandalf would become 'evil' of his own free will, but like the others he would not necessarily consider what he chose to be 'evil'.

Well, that may be true, but self-assessment in such cases is hardly relevant being more than subjective and self-deceiving.

Originally Posted by WCH

One might put it like this: "evil" in Tolkien is not a Thing, an ideology, a Side

I disagree; evil has all those aspects in Ea. It is physical, in the form of the Marring. It is an ideology, in the sense already defined by davem, which I quoted above. It is also a side - Tolkien had no problem seeing that way, when he talked about Bombadil, for example:

Originally Posted by Letter #144

The story is cast in terms of a good side, and a bad side, beauty against ruthless ugliness, tyranny against kingship, moderated freedom with consent against compulsion that has long lost any object save mere power, and so on