The Philosophy of Nosology.

Many scholars believe that psychiatric nosology is undergoing a crisis of confidence. Some of the issues up for debate hark back to the introduction of the natural history approach to classification in the seventeenth century. Natural histories map sameness and difference rather than speculate about causes. In contrast, the natural classification approach aspires to carve nature at the joints by demarcating classifications by causes. Natural classifications are more ideal scientifically, but speculation about causality has had a poor track record in psychiatric nosology. A natural classification of psychiatric disorders may have the added burden of requiring normative assumptions in addition to the discovery of fact. In the natural classification tradition, the epistemic iteration perspective, the Research Domain Criteria (RDoC) initiative, and dimensional models offer different views about the criteria of naturalness (or validity). Also in this tradition, some thinkers believe that causes can be empirically indexed by latent variable models, especially if the latent variables are moderately heritable, but these assumptions may be neither statistically nor genetically warranted.