It is generally known that in J.-K. Huysmans, the fascination with concentrates appears in two semantic fields: in nutrition and in æsthetics. To that, in our view, may be added a third: religion. Through a process we have dubbed “a reduction to the essence,” we argue that the osmazôme alluded to in A rebours, the ptomaïne mentioned in En rade , and the sacred essences discussed in Sainte Lydwine de Schiedam and La Cathédrale express in dialectical terms Huysmans’s fascination with an authentic presence. ( ms ) (in French)