In the ancient world there were four models of disease causation. The first viewed disease as retributive, caused directly by a divinity, usually a god or gods. The second postulated a demonic force as being responsible for inflicting disease on individuals. The third explained disease as the result of magic, often brought by sorcerers or magicians. Finally, the ancients ascribed some disease to natural causes. These etiological models were not mutually exclusive. In most ancient societies, in fact, they were complementary. But the treatment prescribed differed according to the perceived causative factors. When gods were assumed to be responsible, a religious response (e.g., prayer, sacrifice, or purification) was required. When demonic causation was assumed, exorcism or divine healing was called for. If illness was attributed to magical forces, counter-magic was expected to be efficacious. If...