The paper examines a process of fin-de-siècle aesthetics, very present in Monsieur de Phocas by Jean Lorrain and consisting in erasing the boundaries between the categories and qualities of the sensible (sensibilia) and the intelligible (intelligibilia). Our analysis is based on the concept of difference, which brings it close to nescio quid and it intends to undertake a kind of anatomy of one of the vectors of the imagination and poetics of the selected era.
It then offers an answer to the question of whether the constituent elements either of binary structures or of larger sets tie together a relationship of opposition or ambivalence, if not ambiguity.