This thesis stems from a questioning of the instability of the state's discourse in the cultural domain. In effect, since the appearance in the Western world of the first explicit cultural policies, arguments justifying the state intervention in this domain have ceaselessly changed over time, appealing sometimes to notions such as that of 'democratisation of culture', 'cultural democracy', or to notions of 'cultural development', 'cultural economy', or 'cultural diversity'. The inconsistencies that characterise the state's rationales in this domain notably reflect a continuous quest for legitimacy that is worth analysing. Like elsewhere, the consensus over the legitimacy and the purpose of a cultural policy was not easily reached in the Canadian French province, Quebec. Several policy statements have indeed been formulated before the adoption, in 1992, of Quebec's official cultural policy. To understand the evolution of the justifications for state intervention in this field, we analyse three policy statements that were key in the history of Quebec's cultural policy: Pour une politique (1959); La politique quebecoise du developpement cultureI (1979); and La politique culturelle du Quebec: Notre culture, notre avenir (1992). In a first phase, we examine the politico-historical context from which these policy statements emerge. Secondly, we recount the origins of the most important ideas that we find at the core of these statements and which were rooted in the work of intellectuals (such as Edmond de Nevers, Edouard Montpetit, Marcel Rioux, Fernand Dumont) as well as in governmental reports that predated their elaboration. We then analyse the argumentation of each cultural policy statement as well as the critiques they raised at the moment of their publication. These critiques were formulated as much by journalists as by politicians, artists and other professionals working in the field of culture. The analysis of the argumentation is carried out with a theoretical model that has been developed by French sociologist Luc Boltanski and economist Laurent Thevenot, the Economies of Worth. We explore more particularly the concept of 'compromise' such as it was designed in the model. This concept enables us to understand why cultural policies have difficulty achieving consensus. The application of this model to cultural policy has not been attempted before, so this is one of the original aspects of this thesis.