Cults of Unreason is a non-fiction book on atypical belief systems, written by Christopher Riche Evans, who was a noted computer scientist and an experimental psychologist. It was first published in the UK in 1973 by Harrap and in the United States in 1974 by Farrar, Straus and Giroux, in paperback in 1975, by Delacorte Press, and in German, by Rowohlt, in 1976. In 2001 new religious movement specialist George Chryssides criticized the book's title by pointing out that most groups referred to as cults do have well-defined beliefs.