In the first supernatural tradition, also called the demonological method, abnormal behaviors are attributed to agents outside human bodies. According to this model, abnormal behaviors are caused by demons , spirits , or the influences of moon , planets , and stars . During the Stone Age, trepanning was performed on those who had mental illness to literally cut the evil spirits out of the victim's head. Conversely, Ancient Chinese , Ancient Egyptians , and Hebrews , believed that these were evil demons or spirits and advocated exorcism . By the time of the Greeks and Romans , mental illnesses were thought to be caused by an imbalance of the four humors , leading to draining of fluids from the brain . During the Medieval period, many Europeans believed that the power of witches , demons , and spirits caused abnormal behaviors. People with psychological disorders were thought to be possessed by evil spirits that had to be exercised through religious rituals. If exorcism failed, some authorities advocated steps such as confinement, beating, and other types of torture to make the body uninhabitable by witches , demons , and spirits. The belief that witches, demons, and spirits are responsible for the abnormal behavior continued into the 15th century.  Swiss alchemist, astrologer, and physician Paracelsus (1493–1541), on the other hand, rejected the idea that abnormal behaviors were caused by witches , demons , and spirits and suggested that people's mind and behaviors were influenced by the movements of the moon and stars.