The aim of this paper is to show that the novel La Religieuse can be seen as a crucial moment in Diderot’s philosophical reflection on sensibility. In the first part of the article, the author underlines the fact that the apparent contradictions between Suzanne the narrator and Suzanne the character are in fact a conscious application romanesque of medical theories related to the Montpellier School of vitalism. According to vitalists, the only way to understand sensibility is to juxtapose its pathological manifestation and its external evaluation. This is made possible in the novel precisely by the doubling of Suzanne: she is at the same time a suffering body and a neutral observer, patient and physician. In the second part, the author shows how this close connection between the physical-pathological and the moral aspect of sensibility is expressed in a particularly clear way through the use of ‘tears’, which are the primary manifestation of the mysterious bond between body and soul.