Many philosophers and cognitive scientists have argued that our everyday speculations about mental states constitute an informal theory of the causes of behavior, a so-called folk psychology. Folk psychology uses everyday terms such as "belief and "desire," "hunger," "pain," "will," "intent," "motive," and so forth. Such accounts are based upon perceptions and explanations of behavior that humans, through experience, seem naturally to generate. As we will argue, some of the particular folk psychological beliefs upon which criminal law is based do not accurately reflect current psychological knowledge.