[adamc]

Compare to, say, "A Wizard of Earthsea", where magic is explained in a different way that points out that while a wizard could transmute one substance into another, no wizard would, because of the far-reaching ramifications.

The system was not fully elucidated by any means, but the subtlety of it was suggested by such things as Ged deducing that the doorkeeper was one of the seven masters of Roke.