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

“Witchcraft is a more or less solitary form of black magic.” [via, also]

Consider also:

  1. “Black magic is not a myth. It is a totally unscientific and emotional form of magic, but it does get results–of an extremely temporary nature. The recoil upon those who practice it is terrific.”
  2. “Spiritualism–more correctly, spiritism–is not a form of black magic.”
  3. “In the congregational form of the Black Mass the priest, having finished his abominations–these are, quite frankly, indescribable–scatters the fragments of the Host on the floor, and the assistants scramble for the soiled fragments, the possession of which, they believe, will allow them to work their petty and malicious designs.”
  4. “To practice black magic you have to violate every principle of science, decency, and intelligence. You must be obsessed with an insane idea of the importance of the petty object of your wretched and selfish desires.”
  5. “My most memorable personal experience of the effects of black magic occurred when I was living in Scotland. The machinations of a degraded and outcast member of the Order caused my hounds to die, my servants to become insane. The struggle lasted until the recoil of the current of hated caused the luckless sorcerer to collapse.”