Forbidden knowledge
Knowledge secret societies use for membership
Forbidden knowledge is information, sometimes in the form of forbidden books, to which access is restricted or deprecated for political or religious reasons. It differs from secret knowledge in that forbidden knowledge is commonly not secret, rather a society or various institutions will use repressive mechanisms to either completely prevent the publication of information they find objectionable or dangerous (censorship), or failing that, to try to reduce the public's trust in such information (propaganda). Public repression can create paradoxical situations where the proscribed information is generally common knowledge but publicly citing it is disallowed.