The Roman philosopher and physician Claudius Galen formulated a concept of personality types based on the ancient Greek theory of humorism, which attempted to explain the workings of the human body.
The roots of humorism go back to Empedocles (c.495–435 BCE), a Greek philosopher who suggested that different qualities of the four basic elements—earth (cold and dry), air (warm and wet), fire (warm and dry), and water (cold and wet)—could explain the existence of all known substances. Hippocrates (460–370 BCE), the “Father of Medicine,” developed a medical model based on these elements, attributing their qualities to four fluids within the body. These fluids were called “humors” (from the Latin umor, meaning body fluid).
Two hundred years later, Galen expanded the theory of humorism into one of personality; he saw a direct connection between the levels of the humors in the body and emotional and behavioral inclinations—or “temperaments.”
Galen’s four temperaments—sanguine, phlegmatic, choleric, and melancholic—are based on the balance of humors in the body. If one of the humors develops excessively, the corresponding personality type begins to dominate. A sanguine person has too much blood (sanguis in Latin) and is warm-hearted, cheerful, optimistic, and confident, but can be selfish. A phlegmatic person, suffering from excess phlegm (phlegmatikós in Greek), is quiet, kind, cool, rational, and consistent, but can be slow and shy. The choleric (from the Greek kholé, meaning bile) personality is fiery, suffering from excess yellow bile. Lastly, the melancholic (from the Greek melas kholé), who suffers from an excess of black bile, is recognized by poetic and artistic leanings, which are often also accompanied by sadness and fear.
According to Galen, some people are born predisposed to certain temperaments. However, since temperamental problems are caused by imbalances of the humors, he claimed they can be cured by diet and exercise. In more extreme cases, cures may include purging and blood-letting. For example, a person acting selfishly is overly sanguine, and has too much blood; this is remedied by cutting down on meat, or by making small cuts into the veins to release blood.
Galen’s doctrines dominated medicine until the Renaissance, when they began to decline in the light of better research. In 1543, the physician Andreas Vesalius (1514–1564), practicing in Italy, found more than 200 errors in Galen’s descriptions of anatomy, but although Galen’s medical ideas were discredited, he later influenced 20th-century psychologists. In 1947, Hans Eysenck concluded that temperament is biologically based, and noted that the two personality traits he identified—neuroticism and extraversion—echoed the ancient temperaments.
Sources: The Psychology Book (DK)