That curious psychological phenomenon, the involuntary memory, is not an original discovery of Proust. Nor does he claim it as such, since, in Le Temps retrouvé, he himself mentions Chateaubriand, Baudelaire, and Nerval as predecessors. Critical investigations have since amplified this list. What is original, however, is Proust's use of it: only he conceived of its many facets—poetic, dramatic, philosophic— and exploited its possibilities by incorporating it centrally in the substance of a novel. Within his own work the involuntary memory underwent a lengthy evolution, appearing in embryonic form from the outset in Les Plaisirs et les jours and recurring, progressively more refined, in all subsequent writing, but not fully modeled nor centrally placed until the final work. In La Recherche three separate forms of the involuntary memory are delineated. There is a dream memory operating in a state of full or partial somnolence found principally in the “Ouverture” and in La Prisonnière where the senses and imaginative powers pursue a course unchecked by reason or will, where the evocations are fleeting, vague in contour, limited in significance and never surprising. There is a sentimental memory evoking a person once loved by the narrator (Gilberte, his grandmother, Albertine), in effect resuscitating that person since the narrator experiences her as present, as a living reality within him, surrounded by the full force of all old emotional ties.