Hippocrates (460?-377? B.C.), greatest physician of antiquity, was regarded as the father of medicine. Born on the island of Kos, Greece, Hippocrates traveled widely before settling on Kos to practice and teach medicine. His teachings, sense of detachment, and ability to make direct clinical observations had much to do with freeing ancient medicine from superstition. One of the most important contributions of Hippocrates was to set standards for doctors. The Hippocratic Oath has been a guide for medical practitioners for more than two thousand years. In essence, in taking the oath, a physician promises to be honest with patients, to protect and preserve life, and to keep information about patients private. Among his other significant works are Airs, Waters, and Places (400s B.C.), which, instead of ascribing diseases to divine origin, discusses their environmental causes. Three other works-Prognostic, Coan Prognosis, and Aphorisms-advanced the then-revolutionary idea that, by observing enough cases, a physician can predict the course of a disease. The idea of preventive medicine, first conceived in Regimen and Regimen in Acute Diseases, stresses not only diet but also the patient's general way of living.