Castration anxiety is an idea put forth by Sigmund Freud in his writings on the Oedipus complex; it posits a deep-seated fear or anxiety in boys and men said to originate during the phallic stage of sexual development. It asserts that small boys, when seeing a female's genitalia, will falsely assume that the girl had her penis chopped off, probably as punishment for some misbehavior. The boy then becomes anxious lest the same happen to him.