Sade’s work has often been elided from the history of philosophy due to its literary form: it is not in fact composed of philosophical writings in the strict sense, but of fictional writings, especially novels. This article shows, starting from a detailed analysis of the essay Idée sur les romans (1800), how Sade developed a real philosophical theory of the novel, which leads to a narrative vision of philosophy. The peculiar definition that Sade offers of the novel genre – which leads him to question the traditional didactic role of the eighteenth-century novel – allows him to build a perfect synergy between literature and philosophy. The novel is not for him a banal transposition of philosophical discourse, but the mechanism of production of philosophical reflection itself.