This paper focuses on a series of debates, around 1830, about the introduction of public inquiries prior to public works in France, in order to analyze the arguments raised in the discussion and implementation of such procedures. It examines, first, the work of the Commission des routes et des canaux, during the years 1828-29, which discussed and adopted a public inquiry procedure, in continuity with the French tradition of public inquiries, though reorienting it significantly. It then studies a series of alternative procedures, more or less inspired by English parliamentary inquiries, rejecting the French tradition, deemed too administrative and ineffective. It compares these two models of public inquiries, a French tradition, centered on the recording of individual comments and a claim to hear all complaints, and an English-inspired model, focused on the confrontation of arguments mobilized by competing interests. The paper ends by noting a convergence between the debates of the Commission des routes et des canaux and promoters of English inquiries on a number of issues and attempts to characterize the ideal public inquiry around 1830, a procedure for legitimating the sacrifice of some interests in a world of projects.