During the time of Hippocrates, Greek people did not believe demons were the cause of human diseases, so they came up with alternative explanations like Mania, Melancholia and Hysteria. They thought, for example, women's hysteria must be caused by their unstable uterus or other uterus problems. During the time of Roman Empire, there were already descriptions of illusion, hallucination, delusion and the beginning states of psychiatric problems, but nothing was mentioned about the possession of one's physical body of demons.

People were very poor in the Middle Ages, scientific knowledge and skills were not yet available. If someone had gone crazy, people then used fire to burn him, hoping the fire can force the demon to leave the victim's body. Later generations still held on to such beliefs: they thought craziness must be caused by demons, and the more we irritate the demon, the crazier the victim became. Hence people thought they had no other choices but to nail the victim on a cross and burn him to death. There was a period of time in the States when people was frightened of witches, so people gathered together hunting down the suspected witches and burnt them screaming to death on the cross! Although today when we look back to the history, we see that was extremely inhumane, but people lived at the time thought it was nothing but appropriate.

During the time of early Roman Empire, people already thought psychiatric patients must be treated with medication and other medical means but not through chasing away the demons. If we observe patients with mental problems from spiritual study's point of view, we see their windows to the spiritual realm are opened, so as to give other spirits an empty space to occupy. On the other hand, a mentally healthy person's window that opens up to lower-classed Lings' realm is shut down. This is why we always say, "a person with a righteous mind is not afraid of evil beings."