Implications of perturbation strategies: a philosopher of science's perspective

Shifts in the classification of multiple variables can contribute to change in psychiatry's concept of a disorder. These shifts or transitions can occur as a consequence of the expansion of knowledge. A concomitant change in the literal form of diagnostic labels is not required. For example, the definitions of "mass" within the framework of Newtonian and Einsteinian theories are conceptually incompatible even though the same label is used to denote both concepts. Implications of the principles discussed for theory and practice in psychiatry are emphasized.