This dissertation analyzes fictions that, in the second half of the 19th century, illustrate the idea that "sickness is the natural state of a Christian". The elective affinities between religion and pathology interest both realist or naturalistic novelists (such as Émile Zola, the Goncourts, Alphonse Daudet, etc.), whose polemical view aims at demystifying or even medicalizing beliefs, as well as catholic writers (Barbey d’Aurevilly, Léon Bloy, J.-K. Huysmans, Émile Baumann), who emphasize the spiritual meaning of physical afflictions. The parallel between fictions that are all based on the spectacle of a sick believer, but engage contrasting writing styles and currents of thought, shows how much literature crystallises the debate that is going on at the time about Christianism. It also uncovers a point of commonality between writers that critics are used to consider under the restrictive perspective of their opposition. This study aims to highlight the mutual influences that link together several writers who, beyond their differences, base their representation of religious feelings on the same pathological imaginary and the same poetics of incarnation. We argue that the renewal of religious feelings, whether it's in an apologetical or critical perspective, relies on the description of a body which suffers pain, sickness or mysterious psychophysiological disorders. Ultimately, the body conveys considerations about faith, Christian ideology and beliefs and ecclesiastic institutions.