Based on a case study of the inspectorates of the French Ministry of Culture, which are viewed from 1959 to 2021, this article analyzes the process of differentiation used by the central administration’s inspection function. Taking advantage of contributions in the form of the theory of linked ecologies, it highlights what the professionalization of inspectors, at work in the years 1990–2000, owes to internal struggles within the political and then professional ecologies. The inspection report is considered here as a hinge between these two ecologies: as a political resource, it allows some to attest to the rationality of the orientations given to their action programs and their independence from considerations outside the general interest; as an artefact of intellectual work, it allows others to assert themselves as holders of abstract professional knowledge and to demonstrate a capacity for inference through the translation of diagnoses of public policies into operational recommendations.