All of us, at some moment, have had a vision of our existence as something unique, untransferable and very precious. This revelation almost always takes place during adolescence. Self-discovery is above all the realization that we are alone: it is the opening of an impalpable, transparent wall—that of our consciousness—between the world and ourselves. It is true that we sense our aloneness almost as soon as we are born, but children and adults can transcend their solitude and forget themselves in games or work. The adolescent, however, vacillates between infancy and youth, halting for a moment before the infinite richness of the world. He is astonished at the fact of his being, and this astonishment leads to reflection: as he leans over the river of his consciousness, he asks himself if the face that appears there, disfigured by the water, is his own. The singularity of his being, which is pure sensation in children, becomes a problem and a question.