Magic... is an effect in the world when you don't know how it was accomplished.
Alternatively (and perhaps less cynically, and/or more spiritually) magic is an effect in the world brought about by ineffable means. This, in the original meaning of the word ineffable - a thing that cannot be expressed in words. If you can tell people, describe to them how a feat was accomplished, then it isn't magic.
Alternatively (and perhaps less cynically, and/or more spiritually) magic is an effect in the world brought about by ineffable means. This, in the original meaning of the word ineffable - a thing that cannot be expressed in words. If you can tell people, describe to them how a feat was accomplished, then it isn't magic.