The notion of solidarity is an integral component of the language of social protection. The goal of this article is to clarify its meaning by analyzing the French experience. The first part of the article traces the emergence of the discourse on solidarity through a discussion of Léon Bourgeois's work. The second part focuses on the transformations in the meaning of solidarity since 1980. Since then the "crisis" of the welfare state has favored a "return" of this notion in the political realm. Its meaning has nevertheless been distorted: as a tool of "crisis management," it is no longer integrated within a global political and ethical project.