Do possible worlds really exist? Or is there one (actual) world, and infinitely many (im)possibilial Despite sounding like something out of science fiction fantasy or theoretical physics, depending on who you run with, the question of possible worlds has been debated in certain philosophical circles since the turn of the twenti eth century, ranging from set theory in mathematics to modal philosophy to semi otics.1 The link between the three disciplines lies in the ontological fiat, or performative, that brings a possible world into existence, however that existence may be defined. For Umberto Eco, possible worlds are at base cultural constructs, but, then again, so is the real world; for David Lewis, the founder of modal realism, possible worlds are just as real as the real world; and for David Hubert, one of the early developers of mathematical set theory, the set-theoretical universe, which un derpins possible worlds theory, quite simply is paradise.2 My project in this essay is to detect if (and how) the theory of possible worlds may underpin certain aspects of the narrative of drama and performance, and more specifically, the 1990 play, Worlds, by Canadian playwright John Mighton. In order to do so, I will interrogate the seminal article Eco published in 1978 on tex tual semiotics, Possible Worlds and Text Pragmatics: 'Un drame bien parisien', and consider how the theory of possible worlds is transferable to a narratology of drama and performance. In the course of this discussion, though, I also want to peel back two further layers and consider: (1) the way Eco's work depends upon and de parts from the possible worlds theories of philosophy, especially that of Lewis, and (2) the way Lewis and Eco depend upon mathematical set theory. Finally, I hope to put the whole thing back together by appraising how the play Worlds navi gates the theory(s) of possible worlds.3