This article offers a critical engagement with Claude Lefort's arguments about human rights. According to Lefort, eighteenth-century declarations of rights render the notion of "humanity" indeterminable and open it to continuous reinterpretation in democratic struggles. Lefort develops this argument by confronting Karl Marx's critique of the Rights of Man in "On the Jewish Question." Arguing against Marx, Lefort insists that human rights can be reinterpreted time and again precisely because they are assigned not to a concrete subject but instead to an abstract one. Lefort's account illuminates the "theatre of contestation" that human rights set up in modern democracies; as new groups claim these rights and take them in new directions, our existing conceptions of "humanity" and "rights" undergo significant transformations. The goal of this critical intervention is not to leave aside Lefort's crucial argument that human rights introduce us to an indeterminable notion of "humanity".