Black Magic is Not a Myth in Articles by Aleister Crowley.

“In theory there is no limit to the power of magic. A magician is like a mathematician; he has complete control of the symbols as long as he keeps to the rules.” [via, also]

Consider also:

  1. “Nobody stops to look at me in the street. My appearance is, I suppose, that of a simple country gentleman up in town for a weekend. All my notoriety arises from the fact that I am a magician. I AM THE MASTER THERION. Practically my whole life has been spent in the study of magic.”
  2. “In my textbook, Theory and Practice of Magick will be found the definition of the word magic, or magick, as I prefer to spell it, to distinguish the real from the fake. It is ‘the science and art of causing change to occur in accordance with the will.'”
  3. “But these are only superficial things. Magic transcends space and time. All things are possible to an adept, but the virtue of his knowledge and power would desert if he used them for selfish ends or personal gain.”
  4. “According to the rules of magic, I built a terrace with a northern aspect and carted river sand to it. I worked in the breakfast-room at making the talismans which were necessary to my purpose. The sun was streaming into the room, but in vain; there was a darkness which could be felt. The demons, evil forces, had congregated round me so thickly that they were shutting off the light. It was a comforting situation. There could be no more doubt of the efficiency of the operation.”
  5. “The Egyptian Adepts regarded the conceptions of the mind, the aspirations of the soul, the words of the mouth and the functions of the body, as possessing analogies from which a complete system of rules of life and death could be constructed.”