Abstract:The paper highlights the importance of resurrecting the debate about how to define a profession. The drive to define a profession is traced back to the taxonomic approach -encompassing the work of trait and functionalist writers -in which professions were seen as possessing unique and positive characteristics, including distinctive knowledge and expertise. A range of critical challenges to this approach are then considered, particularly as they relate to the role of knowledge and expertise in defining a profession, covering interactionism, Marxism, Foucauldianism and discourse analysis. However, the most effective challenge to the taxonomic approach is considered to be the neo-Weberian perspective based on a less broadly assumptive and more analytically useful definition of a profession centered on exclusionary closure. With reference to case studies, the relative merits of neo-Weberianism compared to taxonomic and other approaches are examined in relation to the role of knowledge and expertise and delineating professional boundaries.