How is it that the Roman decadence, a derogatory term during the Enlightenment, became the fundamental aesthetic reference for a nineteenth century literary movement? Focusing on the intersections of literature, politics, religion, science and art history, this dissertation adopts a diachronic approach to decadence, read against a backdrop mobilizing twentieth century philosophers Vladimir Jankelevitch and Michel Serres. Decadence (Latin cadere, to fall) first designated the fall of the Roman Empire and a falling away from its political, moral and aesthetic norms. Drawing on Petronius and Baudelaire, I crystallize three ways in which philosophers, scholars (“érudits”), and poets faced the troubling notion of the fall : they observe its occurrence, restore its ruins, or praise its beauty. With this in mind, the dissertation closely analyzes eighteenth century topoi that conceive decadence as political instability (Montesquieu, Gibbon), moral corruption (Rousseau, de Maistre), and architectural imbalance (Diderot, Seroux d’Agincourt). The principal emphasis is on the semantic and stylistic value assigned to the term “decadence”. These interdiscursive readings disclose the displacement of decadent topoi : shifting from one context to another, they narrate the fall of the Roman Empire and remain inscribed in the literary production of Decadence. Whereas the Enlightenment underlines the edifying dimension of the Roman example, nineteenth century authors, lapsing into original sin and propelled by thermodynamic loss, salute the expression of the fall. Barbey d’Aurevilly’s writings reveal consistent historical, structural and textual references to Roman topoi, caught up in the arrested completion of political and mechanical cycles. Furthermore, his dandyism and ultramontanism conjure up the Roman conflict, while recurring fragments, maculae and lacunae destabilize the architectural balance of his texts. The Literature of Decadence emerges as an artificial intervention that suspends the irreparable fall, enlightening the political, moral and technological turmoil of the Second Empire with those of the Roman Empire. In returning Decadence back to its Roman origins, and tracing their configuration in the age of Enlightenment, this dissertation unravels a formative, yet frequently overlooked component of nineteenth century literature and aesthetics.