¶2 Nosologies
The classification of mental disorders has been viewed as a subdivision of the classification of diseases in general.
During the enlightenment, great attention was paid to this question. Cullen, for instance, wrote:The art of discerning and distinguishing diseases may best be attained by an accurate and complete observation of their phenomena, as these occur in concourse and succession; & by a METHODICAL NOSOLOGY, or an arrangement of diseases according to their genera and species, established upon observation, abstracted from all reasoning. This arrangement we have attempted in another work.
Some examples of attempts at these tasks are those of Sauvages, Vogel, Sagar, MacBride, and Linnæus. This veritable explosion of classificatory systems in the eighteenth century is itself noteworthy, and characteristic of the encyclopædic period.
Just one of Linnæus's eleven genera of diseases is "mental". His lists, especially the species and sub-species of mental diseases (which are said to involve alienation of judgment), appear, to a modern eye, not so much a classification of sickness as a sickness of classification.