Our received theories of self-deception are problematic. For example, the traditional view, according to which self-deceivers intended to deceive themselves, generates paradoxes: you cannot deceive yourself intentionally because you know your own intentions. Non-traditional views argue that self-deceivers act intentionally but deceive themselves unintentionally or that self-deception is not intentional at all; it involves a mere error (of self-knowledge). The non-traditional approach does not generate paradoxes, but it entails that people can deceive themselves by accident or by mistake, which is controversial. I argue that a functional analysis of human deception solves both problems and a few more. On the functional view, a certain behaviour or trait is deceptive iff its function is to mislead. Thus, while self-deception (may but) need not be intended, it is never caused by an accident or a mistake.
