This article explores the sociocultural and aesthetic frameworks of the 18th century discourse on portraiture. Through selective readings of Rousseau’s ‚La Nouvelle Héloïse‘ and Diderot’s ‚Salon de 1765‘ it aims to describe the cardinal role of affects during the age of sensibility while also highlighting the underlying medial structures through which they come into play. In literary fiction and art criticism, pictorial portraits appear to be embedded in an ambiguous structure of desire, in which the presence of the painting and the absence of the portrayed person are deeply intertwined. Portraits become thus sociocultural devices that are said to provide a sensual presence, substituting the factual absence of the depicted person and reproducing the feelings associated with the latter. In return, the discourse on portraiture is also linked to a fundamental conflict between representation and misrepresentation, as well as the question of the ‘copy’ and the ‘original’, that are both rooted in the paradigm of resemblance.