When a rich English woman, a grouchy scientist, a bonobo monkey and a young man interested in religion meet together in a castle of Provence, what do they do? They talk. And what do they talk about? About the origins of life, the appearance of language, about the secrets of memory, or about the emergence of desire. Subtle and witty, J.-D. Vincent, a neurobiologist, author of The Biology of Passions, offers us here a defense and an illustration of material reason.