This essay analyses John Cleland’s Memoirs of a Coxcomb (1751), his idiosyncratic sequel to the more famous Memoirs of a Woman of Pleasure (1749). As Kathleen Lubey has recently shown, sensuality was part of literature’s repertoire of moral refinement. Indeed, Lubey has argued that erotica acts as ‘a continuous unfolding of epistemology from the details of amorous scenes’, providing a key means of understanding the self and its relation to the world. Yet despite its amorous plot, Memoirs of a Coxcomb emphasises the limits of sensory knowledge. The novel’s comically inadequate narrator is a ‘Dupe of his desires’: a man misled by feeling. Reading Coxcomb as a transmutation of mid-eighteenth-century ‘it-narratives’, this essay argues that rather than constituting and exercising virile autonomy, sexual passion potentially renders the male subject a mere puppet subjected to the mechanistic demands of feeling. Demonstrating a skeptical approach to the role of the body and sensation in the production of knowledge, the novel also provides an intriguing example of its author’s theory of fiction and an exploration of the fate of the author in commodity culture. Challenging the positivist claims of empiricism, the novel’s derisive depiction of the pell-mell of lust illuminates the compulsive self-abnegation of desire, and demonstrates the difficulty of parsing an idea of the self and the world from a deluge of sensory data. Cleland’s novel thus presents sensuality not as a laboratory of masculine self-fashioning, but as an intractable problem for self-knowledge and understanding.