humor, according to ancient theory, any of four bodily fluids that determined human health and temperament. Hippocrates postulated that an imbalance among the humors (blood, phlegm, yellow bile, and black bile) resulted in pain and disease, and that good health was achieved through a balance of the four humors; he suggested that the glands had a controlling effect on this balance. For many centuries this idea was held as the basis of medicine and was much elaborated. Galen introduced a new aspect, that of four basic temperaments related to the elements of which matter was thought to consist (fire, water, air, and earth) and reflecting the humors: the sanguine, buoyant type; the phlegmatic, sluggish type; the choleric, quick-tempered type; and the melancholic, dejected type. In time any personality aberration or eccentricity was referred to as a humor. The medical theory of humors was undermined in the centuries after the Renaissance and lost favor in the 19th cent. after the German Rudolf Virchow presented his cellular pathology.
In literature, a humor character was one in whom a single passion predominated; this interpretation was especially popular in Elizabethan and other Renaissance literature. One of the most comprehensive treatments of the subject was the Anatomy of Melancholy, by Robert Burton. The theory found its strongest advocates among the comedy writers, notably Ben Jonson and his followers, who used humor characters to illustrate various modes of irrational and immoral behavior.
See N. Arikha, Passions and Tempers: A History of the Humours (2007).