Habermas's theory of communicative action provides a useful normative theoretical framework with which to guide the development of service user involvement in health care policy making. To participate in communicatively rational discourse Habermas requires only that participants are competent to speak and act. Through a case study of user involvement in mental health policy making this paper explores what this notion of competence means in practice. It is shown that our competence as participants in discourse is constrained by the power dynamics that operate through identity, and in the case of user involvement through the institutionalized identities of 'service user and 'professional'. The paper argues that Habermas's notion of competence is abstract and asocial, and that this is due to the fact that it is based on an equally abstract concept of the intersubjectively constituted subject. It goes on to argue that in order for Habermas's theory to be capable of doing the normative work that is required of it a revised notion of the intersubjectively constituted subject is needed, one which is embodied and thus more fully social.