The book engages in a polemical critique of recent efforts to revive World Literature models of literary studies (Moretti, Casanova, etc) on the grounds that they construct their curricula on an assumption of translatability. As a result, incommensurability and what Apter calls the "untranslatable" are insufficiently built into the literary heuristic. Drawing on philosophies of translation developed by de Man, Derrida, Sam Weber, Barbara Johnson, Abdelfattah Kilito and Édouard Glissant, as well as on the way in which "the untranslatable" is given substance in the context of Barbara Cassin's Vocabulaire européen des philosophies: Dictionnaire des intraduisibles, the aim is to activate Untranslatability as a theoretical fulcrum of Comparative Literature with bearing on approaches to world literature, literary world systems and literary history, the politics of periodization, the translation of philosophy and theory, and the bounds of non-secular proscription and cultural sanction.