This is a complete transcription of Letter #155:

                    "I'm afraid I have been far too casual about `magic' and especially the use
                    of the word; though Galadriel and others show by the criticism of the
                    `mortal' use of the word, that the thought about it is not altogether casual.
                    But it is a v. large question, and difficult; and a story which, as you so
                    rightly say, is largely about motives (choice, temptations etc.) and the
                    intentions for using whatever is found in the world, could hardly be
                    burdened with a psuedo-philisophic disquisition! I do not intend to
                    involve myself in any debate whether `magic' in any sense is real or
                    really possible in the world. But I suppose that, for the purposes of the
                    tale, some would say that there is a latent distinction such as once was
                    called the distinction between `magia' and `goeteia'[1]. Galadriel speaks
                    of the `deceits of the Enemy'. Well, enough, but magia could be, was, held
                    good (per se), and goeteia bad. Neither is, in this tale, good or bad (per
                    se), but only by motive or purpose of use. Both sides use both, but with
                    different motives. The supremely bad motive is domination of other `free
                    wills'. The Enemy's operations are by no means all goetic deceits, but
                    `magic' that produces real effects in the physical world. But his magia he
                    uses to bulldoze both people and things, and his goeteia to terrify and
                    subjugate. Their magia the Elves and Gandalf use (sparingly): a magia,
                    producing real results (like fire in a wet faggot) for specific beneficent
                    purposes. Their goetic effects are entirely artistic and not intended to
                    deceive: they never deceive the Elves (but may deceive or bewilder
                    unaware Men) since the difference is to them as clear as the difference to
                    us between fiction, painting, and sculpture, and `life'.

                    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 betweeen 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
                    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.(ragorn) is not a pure `Man', but at long remove one
                    of the `children of Luthien'. "

                    [1] Greek equivalent of goetia; the English form Goety is defined in the
                    O.E.D. as `witchcraft or magic performed by the invocation and
                    employment of evil spirits; necromancy.