Having laid this groundwork, we move next to the second purpose of this article and the focus of this special section, by applying our perspective to the assessment and description of psychopathology. As we show, in numerous domains researchers have demonstrated that putative “disorders” actually consist of multiple, homogeneous dimensions of dysfunction that have different correlates and, often, different etiologies. When this is true, the validity of the disorders as anything beyond a conventional abstraction is compromised: A diagnosis that a disorder is present, or an assignment of a symptom count for a disorder, can be misleading. We argue that diagnoses based on homogeneous dimensions of dysfunction have increased validity, and we further argue that such diagnoses can provide improved theoretical clarity, parsimony, and utility.
