19 th century was a period in which the first developments in the etiology, pathogene- sis and treatment of mental diseases took place, insanity was replaced by mental illness, and moral treatment was preferred instead of inhumane isolation and restraining methods. The developments in the field of psychiatry in 19 th century forms a bridge between the darkness of medieval period and the luminescence of 20 th century for the establishment of secular scientific psychiatry. In this article first the theories those were accepted regarding the pathogenesis and treatment of insanity in the 18 th century is explained. Then the developments in 19 th century psychiatry is explained to- gether with the contributions of Philippe Pinel, Jean-Étienne Dominique Esquirol from France; John Conolly, Samuel Tuke from England; and Johann Christian Reil, Wilhelm Griesinger ve Emil Kraepelin from Germany. Finally, the positive and negative consequences, not only for mentally dis- eased, but also for all humanity, of the new paradigm of 19 th century is discussed in the context of the moral therapy which brought humane conditions to asylums and respect for the dignity and honor of the patients and phrenology and degeneration theories.