For more than a thousand years, the humoral theory, derived from Aristotle and Galen, dominated medical and psychological thought. The body and mind were supposed to be ruled by four humors which, in equilibrium, brought perfect health; but the predominance of any one, whether from birth or age or circumstances, produced a certain type of physique and a cast of mind appropriate to certain activities and to a certain social status. The wrong humor in a given situation invited tragedy, for each humor belonged with certain stars and planets. The sanguine humor (blood) was under the astral influence of the planet Jupiter, and was thought proper to princes, to accepted lovers, and to the jovial and the fortunate; but ill-chance could easily sour it to melancholy. The phlegmatic humor under Venus was thought proper to women, children, and voluptuaries, and under the moon (which was regarded as a planet in the old geocentric astronomy) belonged to simpletons and fools. The choleric (yellow bile) under the sun was proper to rulers and self-willed women, and under Mars to soldiers, roisterers, and drunkards. It was considered unlucky. Even more unlucky was saturnine melancholy (black bile), proper to the sick, the frustrated, and the senile; indeed, it might even bring on a manic-depressive psychosis. This system,1 though it sometimes used absurd analogies as evidence, rested in part on sound clinical observation.
Draper JW. The HumorsSome Psychological Aspects of Shakespeare’s Tragedies. JAMA. 2015;313(19):1980. doi:10.1001/jama.2014.11758