Humors are based on Elizabethan notions of physiology, how our bodies are made and work. There are four: blood, choler, bile and black-bile, each of which is closely allied with the four elements that make up all of the universe: air, water, earth and fire. Healthy people had their humors in balance. The sick had an imbalance. Depending upon the symptoms one might exhibit, a certain excess or shortage of a particular humor might be noted and treated in kind. For instance, if one had too much optimism, if they were manic, they might have some blood let to bring them into balance. Humors were thought to be produced by the liver, based upon what one ate and drank, but they were also the result of a natural disposition--a little bit of nature and nurture--heredity and environment.

• Blood and air are hot and moist, indicating a ruddy and optimistic humor.
• Bile (yellow) is hot and dry, like fire. Bile indicates one is fiery complexioned and rageful, hot tempered.
• Phlegm, like water, is cold and moist, indicating one is heavy, cold, and impassive.
• Black-bile,, like earth, is cold and dry, indicating one is melancholic pale, thoughtful, and downcast.