Normal inability versus pathological disability: Why Ossorio's definition of mental disorder is not sufficient

Ossorio's proposed definition of mental disorder as "inability to engage in deliberate action" is evaluated and compared to Wakefield's analysis of mental disorder as "harmful dysfunction." Ossorio's definition is found to be neither necessary nor sufficient for disorder. The most severe problem is its extreme overinclusiveness; normal mental functioning includes many restrictions on deliberate action, and entire nonpathological domains, such as ignorance and lack of skill, are encompassed within Ossorio's definition. Bergner's attempt to defend Ossorio's definition through various construals of its clauses is found to be ad hoc and unsuccessful. It is argued that the harmful dysfunction analysis adequately explains the shared classificatory judgments about disorder and nondisorder that Ossorio's definition fails to explain, and that Bergner's "epistemological" objection to the harmful dysfunction analysis is invalid.