According to the theological idea, diseases were produced by evil spirits, by devils who entered into the bodies of people. These devils could be cast out by prophets, inspired men and priests. While Christ was upon earth his principal business was to cast out evil spirits. For many centuries the priests followed his example, and during the Middle Ages millions of devils were driven from the bodies of men. Diseases were cured with little images of consecrated pewter, with pieces of paper, with crosses worn about the neck--by having plaster of Paris Virgins and clay Christs at the head of the bed, by touching the bones of dead saints, or pieces of the true cross, or one of the nails that was driven through the flesh of Christ, or a garment that had been worn by the Virgin Mary, or by sprinkling the breast with holy water, or saying prayers, or counting beads, or making the stations of the cross, or by going without meat, or wearing haircloth, or in some way torturing the body. All diseases were supposed to be of supernatural origin and all cures were of the same nature. Pestilences were stopped by processions, led by priests carrying the Host. Nothing was known of natural causes and effects. Everything was miraculous and mysterious. The priests were cunning and the people credulous. Slowly another theory as to the cause and cure of disease took possession of the mind. A few discarded the idea of devils, and took the ground that diseases were naturally produced, and that many of them could be cured by natural means. At first the physician was exceedingly ignorant, but he knew more than the priest. Slowly but surely he pushed the priest from the bedside. Some people finally became intelligent enough to trust their bodies to the doctors, and remained ignorant enough to leave the care of their souls with the priests. Among civilized people the theological theory has been cast aside, and the miraculous, the supernatural, no longer has a place in medicine. In Catholic countries the peasants are still cured by images, prayers, holy water and the bones of saints, but when the priests are sick they send for a physician, and now even the Pope, God's agent, gives his sacred body to the care of a doctor. The scientific has triumphed to a great extent over the theological. No intelligent person now believes that devils inhabit the bodies of men. No intelligent person now believes that devils are trying to control the actions of men. No intelligent person now believes that devils exist.