
This is attributed to Pirsig by Richard Dawkins in the Preface to The God Delusion (2006), p. 28, but cannot be found prior to that. It is obviously a paraphrase of the following from Pirsig's Lila - An Inquiry Into Morals (1991): „An insane delusion can't be held by a group at all. A person isn't considered insane if there are a number of people who believe the same way. Insanity isn't supposed to be a communicable disease. If one other person starts to believe him, or maybe two or three, then it's a religion." ( books.google http://books.google.de/books?id=51i6WkGn6qYC&q=%22An+insane+delusion%22; books.google http://books.google.de/books?id=WZtRAQAAQBAJ&pg=PA426)
Disputed
Source: Zen and the Art of Motorcycle Maintenance: An Inquiry Into Values