Philosophers discuss Jerome Wakefield's influential view of mental disorder as harmful dysfunction, with detailed responses from Wakefield himself. One of the most pressing theoretical problems of psychiatry is the definition of mental disorder. Jerome Wakefield's proposal that mental disorder is harmful dysfunction has been both influential and widely debated; philosophers have been notably skeptical about it. This volume provides the first book-length collection of responses by philosophers to Wakefield's harmful dysfunction analysis (HDA), offering a survey of philosophical critiques as well as extensive and detailed replies by Wakefield himself.