Magick in Theory and Practice [Crowley, Aleister] on Amazon.com.au. Magick in Theory and Practice by Aleister Crowley, January 1991, Magickal Childe edition, Paperback 1 Review. xxviii + 436pp. Hardcover. “Magick is the science and art of causing change to occur in conformity with will.”Aleister Crowley was a noted and controversial occultist, ceremonial magician and poet. Uncommonly good collectible and rare books from uncommonly good booksellers. Share