Kraepelin established a psychiatric system based on the "disease unit theory" at the end of the 19th century. At this time, endogenous psychoses, dementia praecox, manic-depressive illness, and epileptic psychosis were regarded as actual psychiatric conditions.
 However, this theory collapsed in just 20 years, and Kraepelin himself destroyed it. There are three reasons for this outcome. First, Kraepelin changed his position from "disease unit theory" to "syndrome theory". Second, dementia praecox was subdivided and subsequently dismissed (Psychiatry, 8th ed). Third, epileptic psychosis was eliminated in Psychiatry, 9th ed.; thus, the concept of a power of life that causes various acute psychotic features and personality bias was also removed.
 Kraepelin's creativity culminated in the 6th (1899) and 7th (1904) editions of Psychiatry. However, Kraepelin's beliefs following the publishing of his study entitled "Phenomenon form of psychosis" (1920) are unclear.
 Approximately 10 years after the DSM-III was released in 1990, the term "neo-Kraepelinian" began to be used. However, this new concept does not express the importance of Kraepelin's achievements and his suffering.
 Despite his ruthless and gloomy appearance, a tropical-rainforest-like festiveness seems to have persisted inside Kraepelin.
 Author's abstract