Developed by ancient Greek thinkers in the 5th century BCE, the theory of the four humors continued to develop during the Medieval Period. This theory explains precisely how the body works, including how illness, pain, and even personality, form inside a person.
Only falling out of style with the scientific advancements of the 18th century, this theory’s longevity can be attributed to its approach to all life as consisting of four parts, corresponding with the four elements, four seasons, and four temperaments. The theory’s methods for diagnosis and treatment approached medicine as a scientific topic—the first medical model in the world to do so—allowing it to beat off criticism and alternative methods for thousands of years.
Empedocles and the Four Elements
In the mid-5th century BCE, the philosopher Empedocles devised a theory that divided human life into four elements: fire, water, air, and earth. He wrote, “Now hear the fourfold roots of everything: enlivening Hera, Hades, shining Zeus. And Nestis, moistening mortal springs with tears.” He connected each element with a divine power to illustrate how they rule the universe.
Empedocles used four properties to describe the four elements: hot, dry, wet, and cold. Each element opposed each other in its properties. For example, water was wet and cold, so it opposed fire which was hot and dry. These properties were used as the foundation for Hippocrates’s theory of the four humors, positing four “roots” to the human body.
Hippocrates’s Original Theory
Hippocrates had a monumental impact on the science of medicine. Even now, his legacy still shines as he was the first to record the belief that disease occurred naturally, not from any divine power. When Hippocrates was born in the 5th century BCE, medicine and religion were closely, if not entirely, linked. Hippocrates changed this, calling for separation between the two subjects.
In On the Nature of Man, Hippocrates wrote:
“The Human body contains blood, phlegm, yellow bile, and black bile. These are the things that make up its constitution and cause its pains and health. Health is primarily in which these constituent substances are in the correct proportion to each other, both in strength and quantity and are well mixed. Pain occurs when one of the substances presents either a deficiency or an excess or is separated in the body and not mixed with others.”
In his attempt to theorize how disease and pain form naturally in the body, Hippocrates used Empedocles’s four elements and transcribed them onto the body, coming up with the four humors: blood, phlegm, yellow bile, and black bile. Each of these humors shares properties with one of the elements — phlegm (water) is cold and wet, blood (air) is hot and wet, yellow bile (fire) is hot and dry, and black bile (earth) is dry and cold.
According to Hippocrates’s theory, these four humors must be perfectly mixed in the body to produce good health. An imbalance of these humors was the direct cause of disease and pain, either by a detriment or excess in the body. Thus, treatments based on Hippocratic medicine usually involved some form of bloodletting, dieresis, or catharsis.
Although Hippocrates may not have invented this theory—it may actually have originated from ancient Egypt or Mesopotamia—he was the first to systematically apply it to medicine.
The Creation of Hippocratic Medicine
The Hippocratic ideal for medicine, created in the 6th century BCE, sought to give medical professionals signs to look out for in order to diagnose patients and cure their ills. An imbalance of humors was the direct cause of any and every medical issue, so medical professionals could study the amount of humors in a patient’s body to diagnose and treat them.
Someone could have a humor imbalance due to a variety of factors, including their diet, their activity, and their contact with the environment around them. For example, Hippocrates hypothesized that people from different climates would face different issues based on how the properties of their humors (wet, cold, dry, warm) interacted with the properties of the world around them.
In addition to his theory of the four humors, Hippocrates contributed many different medical diagnoses and treatment methods to medicine. He began the practice of categorizing illnesses as acute, chronic, endemic, or epidemic. Hippocrates also contributed to the study of pulmonary medicine by studying the symptoms of respiratory disease. His findings and theories were used as the model for ancient and medieval medicine for centuries.
Where Did the Humors Come From?
Hippocrates believed that the digestion process was the center of human production. During this process, as food makes its way through the organs, each humor is formed one at a time: first, blood, then phlegm, then yellow bile, with black bile coming last. An imbalance would appear if something needed to be fixed within the production process, causing too much or too little of one humor to develop. Thus, the stomach and liver were the center of attention for the Hippocratic model, which saw diet and digestion as being the fundamental root of illness and its treatment.
Theophrastus’s Connection of Personality With the Humors
Theophrastus was an ancient Greek philosopher active in the 2nd and 3rd centuries BCE. He developed multiple theories throughout his life and even became Aristotle’s successor at his school in Athens. One of Theophrastus’s ideas was that personality is fundamentally connected with the four humors.
The four humors are not only based on the theory of the four elements but also on the ancient idea of four temperaments: sanguine, choleric, melancholic, and phlegmatic. A person with an imbalance of one humor within them was said to have one of these personality types. Someone with too much blood was said to be sanguine. Too much phlegm and you were phlegmatic. An overflow of yellow bile made you choleric, and an imbalance of black bile meant you were melancholic.
These naturally occurring personalities appeared in thousands of ways in ancient, medieval, and early modern periods, especially within art. From characters within Chaucer’s Canterbury Tales to Shakespeare’s Taming of the Shrew, artists throughout history took inspiration from Hippocratic medicine to create some of their most convincing protagonists, antagonists, and everything in between.
Galen’s Development of the Theory
Roman medical theorist Galen, active in the 2nd and 3rd centuries CE, years after the formation of Hippocratic medicine, developed Hippocrates’s theory further. In his On the Temperaments, Galen expanded Hippocrates’s theory to illustrate how certain people can be naturally predisposed to certain diseases, as opposed to everyone being born with naturally healthy bodies.
Galen also argued that blood was the most prevalent humor and contained all three other humors within it. Because of this, medical professionals used blood for diagnosis, as well as utilizing it as a fundamental basis for treatment plans. Galen also developed Theophrastus’s model, by theorizing that mood can cause an imbalance, not just the other way around. For example, too much anxiety could cause a buildup of black phlegm, thus creating a system where mind and body are linked through one theory of medicine.
Galen is also responsible for drawing a connection between the four humors and the four seasons, writing: “As for ages and the seasons, the child corresponds to spring, the young man to summer, the mature man to autumn, and the old man to winter.” The four seasons corresponded to the changes a person experiences throughout their lives. Each season was related to properties based on Empedocles’s model and given a corresponding humor.
This meant that during different periods of a person’s life or at certain times of the year, they would face a natural disposition toward certain imbalances, impacting diagnosis and treatment. In the West, Galen’s model of human anatomy, based on the Hippocratic theory, would become the point of reference for all medical theory and practice for the next 1300 years.
Other Humor Models
While the Hippocratic model of the four humors was widely popular in Europe during ancient and medieval times, other people throughout the world adopted other models that conformed more closely with their beliefs.
The Indian Ayurveda model was based on five elements — adding ether to Empedocles’s list of fire, water, earth, and air. This model believed in three humors as opposed to four, while still maintaining the theory that the humors must be balanced for good health. Other models included two, three, or six base elements from which to base medical theories.
Influence on Modern Medicine and Culture
The 19th-century theory of germs and bacteria as a cause for the spread of diseases made Hippocratic medicine obsolete. This new scientific basis proved that each disease, illness, and pain had specific and unique causes, differing from the all-inclusive humeral approach to medicine.
Regardless of the demise of the theory of the four humors, Hippocrates’s argument still lives on in medical terminology, in which the terms “humoral immunity” or “humoral regulation” are sometimes used to describe hormones or antibodies.
The theory of the four humors is often brought up in pop culture — bloodletting with leeches or medieval methods to induce throwing up are frequently shown as methods of medical treatment. Understanding the theories behind these scenes in documentaries and fictionalized accounts will aid you in understanding how people once viewed the human body. Although we do not live by the idea of the four humors anymore, it has impacted human culture and medicine for two millennia, which means you will likely come across this idea often.
