Ideas about the origin and cure of disease in the middle ages were not purely secular, but included factors such as destiny, sin, and astral influences. The efficacy of cures was similarly bound in the beliefs of patient and doctor more than in empirical evidence, so that physical remedies were often subordinate to spiritual intervention.
The theory of the four humours (bodily fluids of blood, phlegm, yellow bile, and black bile) arose out of Greek philosophy in an attempt to relate all things to universal laws. And so we have parallels drawn between particular aspects of the surrounding world. The humors were oftentimes attributed to appropriate seasons, properties such as hot, cold, dry, and wet, signs of Zodiac in groups of three, four ages of mankind - infancy, adolescence, adulthood, and old age, and even sometimes to the four Evangelists - Matthew, Mark, Luke, and John, as well as the compass directions. (Even now, we still use words "choleric", "sanguine", "phlegmatic" and "melancholy" to describe personalities.) Such balance and classification of the world was of utmost importance, hence the balance of humors within a human body was necessary for health. The physician evaluated the patient's home climate, their normal diet, and astrological charts during consultation. The heavens influenced every person in different ways by influencing elements connected to certain humors, important information in reaching a diagnosis. The physician could determine which humor was unbalanced in the patient and prescribe a new diet to restore that balance. Diet not only included food to eat or avoid but also an exercise regiment, medication, and blood-letting.
