Both sides live mainly by 'ordinary' means. The Enemy, or those who have become like him, go in for 'machinery' – with destructive and evil effects — because 'magicians', who have become chiefly concerned to use magia for their own power, would do so (do do so). The basic motive for magia – quite apart from any philosophic consideration of how it would work – is immediacy: speed, reduction of labour, and reduction also to a minimum (or vanishing point) of the gap between the idea or desire and the result or effect. But the magia may not be easy to come by, and at any rate if you have command of abundant slave-labour or machinery (often only the same thing concealed), it may be as quick or quick enough to push mountains over, wreck forests, or build pyramids by such means. Of course another factor then comes in, a moral or pathological one: the tyrants lose sight of objects, become cruel, and like smashing, hurting, and defiling as such. It would no doubt be possible to defend poor Lotho's introduction of more efficient mills; but not of Sharkey and Sandyman's use of them.
Anyway, a difference in the use of 'magic' in this story is that it is not to be come by by 'lore' or spells; but is in an inherent power not possessed or attainable by Men as such. Aragorn's 'healing' might be regarded as 'magical', or at least a blend of magic with pharmacy and 'hypnotic' processes. But it is (in theory) reported by hobbits who have very little notions of philosophy and science; while A. is not a pure 'Man', but at long remove one of the 'children of Luthien'.
The Letters of J.R.R. Tolkien (#155) not sent
25th September 1954