What do we mean when we say that a person A has a right to X? The article discusses this question by outlining an account of the foundations of rights and of the significance and role of right claims in the normative evaluation of political action. The effectiveness of the language of rights, it is argued, depends on the availability of such an account. Moreover, it also allows to meet three major objections to the concept of Human Rights: its non universality; its moral individualism; and that of the act-consequencialist view according to which in evaluating political action no room is left to moral rules such as Human Rights.