 What lessons can be drawn from the study of a hazard that occurred during a collective philosophical inquiry in a school context ? 
The article presents an analysis of an extract from a Collective Philosophical Inquiry. Through this case study, we show the possible misunderstandings linked to the duality of two « worlds » : that of the teacher who experiments with CPI in her classroom and that of the researcher who is responsible for the design of this type of session. The « world » is defined as « conceptual, axiological and praxical background ». The confrontation between these worlds therefore questions both the modalities of their necessary collaboration and the conditions of the construction and use of a true « professional genesis.