Even though the definitions in the third edition of the American Psychiatric Association's Diagnostic and Statistical Manual were supposed to be descriptions of clinical syndromes, the third and later editions of the DSM have included diagnostic categories for conversion disorder and various forms of somatization disorder, which represent an assertion of causality, not an observation of a clinical syndrome. Although these "disorders" represent etiologic diagnoses, the definitions provide no validated method for establishing causality in individual cases. Nor is there any validated methodology for making a presumptive diagnosis. Thus, it is impossible to make a diagnosis of conversion disorder or a somatization disorder without making an error in reasoning. These diagnostic categories should therefore be excluded from the DSM-V.