Abstract
The concept of progressive hereditary degeneration, which significantly influenced medical, particularly psychiatric and in turn social thought of the second half of the 19th century, was articulated by Bénédict Augustin Morel. The distinguished French psychiatrist developed the theory of degeneration and created the nosological framework of the heredity of mental illness in order to explain the more frequent psychoses and nervous disorders. In the absence of patho-anatomical findings, Morel attributed these phenomena to hereditary causes. His theory was the first attempt to interpret insanity, mental disorders, and criminality, across generations, and formed the basis for the further development of psychiatry. It had a notable influence on many scientific disciplines of the time, such as criminology, anthropology, biology, and general pathology. It would later result in the emergence of eugenics, which raised several moral issues and would ultimately be used in many ways to justify segregation. Morel was mainly influenced by the monogenetic degenerative theory and believed that social progress could be achieved by the coupling of psychiatry, a social medicine, with philosophy and Christianity.