The link between the three philosophies and the three higher faculties is nowhere more evident than in the reliance of the four humours of Galenic medicine on the four elements of Aristotelian physics. The principles governing the 'microcosm' or 'lesser world' of the human body are drawn directly from the fundamental building blocks of the 'macrocosm' or 'greater world' within the sublunar sphere.
Each of the humours originated in a different bodily organ. The harmonious balance of these four humours produced health in the body: illness resulted when this balance was disturbed.
The mind and the body were intimately related: the dynamic equilibrium of the four humours was closely linked with four sets of temperaments, or traits of personality and character.
Together, the four elements, humours and temperaments were likewise associated with the four seasons of the year and the four ages of man. The cycle of life was linked in turn to the cycle of the year reinforced further associations of the four humours with six of the seven planets, which provided one of the bases for astrological medicine.
Blood, like air, was hot and wet. Physiologically, it was believed to be produced exclusively by the liver. Psychologically, it was associated with a 'sanguine' temperament, that is, a personality or disposition that is lively, enthusiastic, and sociable, which corresponds to childhood, spring, and Jupiter, the most benign of the planets.
Yellow bile, like fire, was hot and dry, and therefore associated with fire of youth or early manhood, with the Sun and Mars. Originating in the gallbadder, an excess of it was thought to produce aggression, which it turn could result in derangement of the liver and imbalances in the other humors.
Black bile, like earth, was cold and dry. The Greek word for 'black bile' μέλαινα χολή (melaina kholé) is the root of the English world 'melancholy'. Produced in the spleen, black bile, in excess, was understood to cause depression, which conversely could cause the liver to produce blood contaminated with black bile. It was associated with autumn and middle or declining age, as well as with the Moon and Venus.
Phlegm, like water, was cold and wet, and associated with winter, decrepid old age, and Saturn, the most malign of the planets. The condition with which it was associated is captured in the English word 'phlegmatic', which describes listless, apathetic behaviour.
Resources: A good introduction to the four humours can be found in Melvyn Bragg's radio programme, 'In Our Time'.
The idea that the body is a concoction of these four essential juices is one of the oldest on record. From the Ancient Greeks to the 19th century it explained disease, psychology, habit and personality. When we describe people as being choleric, sanguine or melancholic we are still using the language of the humours today. It also explains why, in the long and convoluted history of medical practice, pigeon livers were an aphrodisiac, blood letting was a form of heroism (and best done in spring) and why you really could be frightened to death. The theory was dismantled from the 17th century but in its belief that the mind and body are intimately connected and that health requires equilibrium the humours retain an influence to this day.