 In the very first paragraph of Le Rêve de D’Alembert, the character D’Alembert, who is a partisan of substance dualism and is challenging the character Diderot—a materialist—to account for the existence of consciousness and thought, introduces the problem of sensibility (sensibilité, better translated “sensitivity”) as a property. Referring to a discussion that seems to have occurred before the text begins, he declares to Diderot, “this sensitivity … if it is a general and essential quality of matter, then stones must sense” (DPV XVII, 90). Diderot states, revises, emends and restates this materialism of living, sensing matter in a variety of works, both in the Rêve and in his more “empirically” oriented writings such as the Principes philosophiques sur la matière et le mouvement and the Eléments de physiologie.