Abstract This article interprets the central erotic triangle between Lily Bart, Lawrence Selden, and Simon Rosedale in The House of Mirth (1905) as a modernized restaging of the love triangle in Madame de Lafayette’s La Princesse de Clèves (1678). Through the lens of the seventeenth-century French novel, which Wharton characterized as inaugurating the debut of “modern fiction” in The Writing of Fiction, readers can see how Wharton condemns, in The House of Mirth, the stated motivations of its characters as fundamentally unreliable and their attempts at self-knowledge as futile. In this way, both novels highlight epistemological failures—whether about love, friendship, or status—when characters falter just on the brink of attaining their desires. The last part of this study examines Rosedale’s love for Lily, his active care for her, and his jealousy, which have not received adequate scholarly attention, as well as proposes a new reading of Lily’s rejection of Rosedale’s last marriage proposal.