This article presents a unified theory of irony which claims, with the help of Fauconnier's (1985) mental space theory, that an ironical utterance refers to the mental space of a mutually manifest expectation. According to this view, what a typical ironical speaker does is to say without any distinct space builders that something is the case in the mental space of expectation in order to make it mutually manifest that it is not so in the initial reality space. This expectation space theory of irony integrates the explanatory power of Sperber and Wilson's (1986) echoic interpretation theory with the descriptive power of the view of irony as relevant inappropriateness. (Yoshihiko Kihara )