AbstractDuring the second half of 19thcentury, psychiatry developped into a natural science as a part of medicine. Towards the end of the century, the medical model of mental illness got into a crisis which led to a restriction of somatopathological explanation of psychopathological phenomena, an accentuation of empirical and psychological description of the clinical facts, and a reception of phenomenology and psychoanalysis into psychiatry. Thus, the idea of mental illness as an etio‐pathogenetical and symptomatical unit, based on a cerebral alteration or process, has been given up in favour of clinical types or syndroms of mental disorder without a close connexion with an organic substratum. In consequence of these trends, the modern pluralistic concept of mental illness has been establishe