Magick is the Science and Art of causing Change to occur in conformity with Will.
(Illustration: It is my Will to inform the World of certain facts within my knowledge. I therefore take "magical weapons", pen, ink, and paper; I write "incantations" — these sentences — in the "magical language" ie, that which is understood by the people I wish to instruct; I call forth "spirits", such as printers, publishers, booksellers and so forth and constrain them to convey my message to those people. The composition and distribution of this book is thus an act of Magick by which I cause Changes to take place in conformity with my Will.)
In one sense Magick may be defined as the name given to Science by the vulgar.

Introduction. - Magick Book IV : Liber ABA - Part III : Magick in Theory and Practice (1929)