(A) Psychiatric science has developed around the idea of “insanity” understood as a malformation of the individual human personality. E. Kraepelin’s “naturalistic and systematic” nosography was organized with the idea of “purity” of clinical types. The “entities” he established were the set of deviations of each mental illness’s symptoms and its evolution into an autonomous species. The two major entities identified by Kraepelin (‘manic-depressive psychoses’, today known as ‘bipolar disorder’, and ‘dementia praecox’, today schizophrenia), in isolation and opposition to each other, remain the most typical and purest forms of mental pathology. Such typicality and purity can only arise from the human constitution and their ‘endogenous’ nature.