We still cannot clearly answer the question "what is schizophrenia?" on a material level. Schizophrenia is not guaranteed to exist at this level as a well-definable entity but continues to remain in our thinking as an ideal type. Taking a bird's-eye view of the history of schizophrenia research reveals two directions. One is the pursuit of the causal associations of schizophrenia, and the other is the pursuit of understanding based on meaningful associations. In the pursuit of causal associations, schizophrenia is considered to exist as a disease entity and the aim is to investigate its physical basis. This line of research started with Kraepelin, who aimed to establish schizophrenia as a disease entity, was followed by Schneider, who was committed to the improvement of diagnosis, and is seen in the empirical methodology of DSM-III and beyond. Understanding based on meaningful associations did not attempt to reduce schizophrenia to a physical level, but rather strove to reveal the nature of schizophrenia at a metaphysical level. Starting with Bleuler, anthropological psychopathology and American psychoanalysis were the prevailing trends. Psychiatry uses a social scientific methodology characterized by an ideal type at the stage of grasping the research target and tries to fully utilize the methodology of the natural sciences for pursuit from the perspective of somatic medicine. The question of "What is schizophrenia?" highlights the dilemma of modern psychiatry.
 Author's abstract