This analysis, based on a corpus of texts by teenagers posted on www.filsantejeunes.com, tries to take the measure of the issue of the impossibility of expressing in language the experience of sensing the world – since most of these texts are content to limit themselves to elaborating discourses about the body, its difficulties at being a source of happiness, at conforming to norms of beauty, and do not deal with the phenomenon,namely the experience of perceiving the world. The theory of instances, or of the grounding of utterance, elaborated by Jean-Claude Coquet, can explain this impossibility of expressing in language the experience of sensing the world : it is due to a conflict between the two instances, the grounding in the subject or in the non-subject. This conflict, which has no solution, can lead to bulimic or anorexic behaviour, whose consequences are dangerous to the health, or even to the life of the subject. Psychotherapy, in such cases, should aim at conciliating the instances. Furthermore, these texts produced by teenagers are examples of autobiographical writing, a genre teenagers like a great deal, and thus also enable a contribution to the genesis of the genre, where the adult subject has differed taking up again past experiences of a grounding in the non-subject – that is, physical experiences of direct encounter with the world.