Written over the last 20 years of his life, Marcel Proust reflected on the pages of In Search of Lost Time about the meaning of existence and concluded that only pain allows us to "develop the forces of the spirit." Each pain disfigures our face, "like those faces of old Rembrandt", but pain is a force that can be transformed into another, "let us accept, then, the physical damage that it causes us in exchange for the spiritual knowledge that it brings us".

But how to carry out this transformation from one force to another, from pain to knowledge?