The notion of harm has been a recurring and a significant notion in the characterization of mental disorder. It is present in eminent diagnostic manuals such as DSM and ICD, as well as in the discussion on mental disorders in philosophy of psychiatry. Recent demotion of harm in the definition of mental disorders in DSM-5 shows a general trend towards reducing the significance of harm when thinking about the nature of mental disorders. In this paper, we defend the relevance of (...) the notion of harm in the characterization of mental disorder against some of these attacks. We approach this issue by using the method of conceptual explication pioneered by Rudolf Carnap. Within this framework, we argue that keeping the notion of harm not only helps to discriminate what is pathological from the nonpathological but also prevents potential misuses of psychiatric authority. (shrink)