At present, psychiatric disorders are characterized descriptively, as the standard within the scientific community for communication and, to a certain extent, for diagnosis, is the DSM, now at its fifth edition. The main reasons for descriptivism are the aim of achieving reliability of diagnosis and improving communication in a situation of theoretical disagreement, and the Ignorance argument, which starts with acknowledgment of the relative failure of the project of finding biomarkers for most mental disorders. Descriptivism has also the advantage of (...) capturing the phenomenology of mental disorders, which appears to be essential for diagnosis, though not exhaustive of the nature of the disease. I argue that if we rely on the distinction between conceptions (procedures of identification) and concepts (reference-fixing representations), which was introduced in the philosophical debate on the nature of concepts, we may understand a limited but valid role for descriptive characterizations, and reply to common objections addressed by those who advocate a theoretically informed approach to nosology. (shrink)