Beyond the categorical–dimensional dichotomy: An exercise of conceptual geography in the domain of personality disorders.

Ludwig Wittgenstein (1953/1999, p. 232) has famously remarked that in psychology "there are experimental methods and conceptual confusion," and his harsh comment does not seem to be outdated. To clear up the confusion in question, the methods of conceptual analysis can be used such as Gilbert Ryle’s logical geography or Peter Strawson's conceptual grammar. A promising area of their application can be psychiatric nosology including, especially, the domain of personality pathology. To contribute to logical and methodological clarity concerning the latter, the following steps have been taken. First, a well-established opposition between dimensional and categorical conceptualizations was explored with special attention drawn to considerable crudeness of an idea that this dichotomy alone can fully reflect the conceptual complexity at hand. To do justice to the latter, the classical idea of monothetic classification was introduced and investigated in terms of its background assumptions. The analyses conducted by Peter Zachar and Nick Haslam, in particular, were referred to in order to show not only the monothetic model's relationship to the notion of a natural kind, essentialism, and the disease model, but also these latter ideas' internal heterogeneity. The variety of problems faced by psychiatric essentialism and the natural kind view was then summarized together with a more liberal approach of polythetic classification adopted by the Diagnostic and Statistical Manual of Mental Disorders. The whole "galaxy of ideas" (Ryle, 1971, p. 202) pertinent to the deceptively simple categorical-dimensional dichotomy, finally, was served as a reliable indication of the latter distinction's insufficiency.