For persons interested in the classification of psychopathology, this document will draw some crucial, if counterintuitive, distinctions. While the terms used arise from the philosophical literature, the concepts can readily be applied to increase one's understanding of psychodiagnostic classification, an area of perennial concern to a wide array of researchers and clinicians in psychology, psychiatry, and related disciplines. My aim is to dismantle the assumptions underlying the current diagnostic system, the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV, American Psychiatric Association, 1994), clearing the way for a new understanding of the classification enterprise, one that embraces realism as a goal, fallibilism as a method, and dimensions as a (perhaps yet-to-be-realized) empirical finding.