Aleister Crowley is an author and occultist who is often referenced in the book. Although Crowley is deceased at the time of the action in the book, his theories and beliefs are often retold by Wilson. Wilson admits that some parts of Crowley's life mark him as an evil man, but he continues to be interested in Crowley's methods. Crowley is a source of many of Wilson's theories, including about the star Sirius being a source of messages to Earth.