This dissertation examines the motif of the idiom in Derrida. It argues that, for Derrida, before language can be thought in its generality, there must be a multiplicity of languages or idioms, each of which, while irreducibly different from its others, is simultaneously irreducibly different from itself. This irreducible difference, or idiomaticity, puts the idiom into an originary state of translation that is paradoxically double. On one hand, the idiom, in differing from itself, is constitutively undergoing translation. On the other, the idiom’s irreducible difference from its others forestalls translation, leaving it in a state of untranslatability that is simultaneously a state of non-self-identity. This non-self-identity I tie to an originary metaphoricity. I argue that, in Derrida, metaphor and translation form a conceptual knot through which a general idiomaticity, which I associate with the possibility of literary invention, may be glimpsed. This idiomaticity I find to be at odds with prevailing accounts of translation such as can be found in contemporary scholarship on world literature, where the circulation of texts across lingual borders is a crucial problem. Chapter one argues work on world literature tends to conceive this circulation against a presupposed horizon of metalingual positing. The translational circulation of literary texts serves to manifest, in essentially dialectical fashion, the synthetic whole of language itself. I link this lingual self-manifestation to the gradual appearance of the world, the transcendental ground on whose basis literary texts belonging to particular idioms may show up and enter into global circulation. Chapter two elaborates, through Derrida, a universal law of the idiom that, paradoxically, can be formulated only idiomatically. Briefly, it would fall to a given idiom to prescribe a generalized idiomaticity, even as said idiom prescribes an idiomaticity proper only to itself. Chapter three argues that, for Derrida, the idiom’s (un)translatability entails its originary, but non-dialectizable, spatialization. The idiom is not a means by which the whole of the world may come to light, but rather disrupts the world’s appearance as it resists being integrated therein. Where the idiom shows up in the world to be read is consequently perpetually in question.