Major figures in the early history of abnormal psychology. Greek physician who believed that mental disease was the result of natural causes and brain pathology rather than the demonic activity. Greek philosophers believed that patients with mental illness should be treated humanely and should not be held responsible for their actions. Greek philosopher and a pupil of plato believed in the hippocratic theory that various agents, or humor, within the body, when imbalance was responsible for mental disorders. Aristotle rejected the notion of psychological factors as causes of mental disorders. Galen (a. d. 130 - 200) greek physician who contributed much to our understanding of the nervous system. Galen divided the causes of mental disorders into physical and mental categories. Avicenna (c. 980-1037) ancient persian physician who promoted principles of humane treatment for people with mental disturbances at a time when western approaches to mental illness were inhumane. Hildegard (c. 1098-1179) was a remarkable woman, known as the.