Nowadays, the notion of public interest is a juridical concept as well as a rhetorical topos. Its use, which been widespread in France in the second half of the eighteenth century, is inseparable from a constitutive ambiguity: the debates about its definition crystallize, from the time of the revolutions, the stakes of the modern characterization of the State and its right. Thus it is not surprising that this notion was carried by thinkers who can be linked to the liberal tradition (Locke or Hobbes, often associated with the premises of liberalism), and by others, closer from the egalitarian (Proudhon) or republican (Rousseau, Léon Bourgeois) tradition. The reference to the public interest always corresponds to a particular position in the politico-philosophical field. The contributions of this issue aim to demonstrate that every conceptualizations of the public interest, including critical ones, implie a conception of man and his rights, as well as a social project.