Comment se forment les dispositifs de jugement ?. Une analyse socio-historique des activités de conseil (1912-1952)

How do some highly symbolical professional activities ? such as consulting activities ? succeed in creating the faith that is necessary to the continuation and the development of their markets? Provided it is from a historical perspective, taking into account field effects, the distinction made by Lucien Karpik between impersonal faith and personal faith is granted with heuristic value as for the analysis of how the consulting market works. Coming from the fights, back to the mid-19th century, that were opposing ?civil engineers? or ?consulting engineers?, backed by private industry, to state engineers, the role model for liberal profession ? which lawyers embody perfectly ? is carried out by a fraction of consulting engineers. Competing for the market with senior officials and entrepreneurs, those consulting engineers seek to impose some impersonal guarantees about their independence and competencies on their profession. With the extension, during the first World War, of consulting activities to the new ?work sciences? field, such a liberal model soon had to compete with another form of regulation of the profession, based on personal relationships networks involving leading employers and engineers specialized in work rationalization. This article analyses the fights that took place during the first part of the 20th century between those two fractions of the ?consultants? group, altogether with the conditions why, within the authoritarian context of Vichy, plans of creating an Order for engineering consultants eventually failed.