'The literature of ideas' was first introduced into critical vocabulary by Balzac in the late 1830s, as one side of a terminological opposition in which Romanticism, or what Balzac termed 'the literature of imagery', formed the other (Lost Illusions 356-57). Although for Balzac the literature of ideas preceded Romanticism -it was exemplified by the writings of Diderot, Voltaire and Sterne- it was nonetheless a literary style or school that could be posited only retrospectively, following its belated recurrence in historically alien circumstances. As Jorge Luis Borges and others have noted, aesthetic causality tends to work retroactively: allusions, for example, transform the ways in which their source texts are read, while period styles only come into focus after the fact (Borges; Morton). This is one reason why the temporal schemas with which literary history operates are almost never straightforwardly chronological. Literary history reads backwards, each present constructing its own prehistory. For Balzac, Romanticism changed the ways in which even the literature that preceded it could be read, prompting the subsumption of pre-Romantic texts within this new critical category coined after and against Romanticism.