By Dorsey Armstrong, Ph.D., Purdue University
The absurd sciences of the Middle Ages were based on the theories of the Greek physician Galen, according to which basic health was determined by the balance of the humors in the body. These were considered the four main substances that regulated everything the body did. Blood was associated with air, phlegm with water, yellow bile with fire, and black bile with earth.
So You Have Too Much Blood
The humors were also connected to ideas about appearance and personality types. In turn, based on someone’s personality type, or dominant humor, a certain course of treatment for the disease might be prescribed for them that would be different from the course prescribed for someone else who was suffering from the same affliction but who had a different dominant humor.
For example, if someone had too much blood—or, in medieval medical terms, they were too sanguine—their physician might actually perform bloodletting on them to try and bring their humors back into balance.
If it sounds terrifying to think that someone might try and heal a patient by draining blood out of them—and thereby making him or her weaker, and less able to fight off infection or disease—consider the fact that most medieval physicians also believed that blood circulated through different channels on different sides of the body—so sometimes a person might be bled on the left side, sometimes the right, and sometimes both.
This is a transcript from the video series The Black Death: The World’s Most Devastating Plague. Watch it now, on Wondrium.
The Absurd Science of the Four Humors
If someone had too much phlegm, and thus their body was too moist and too cold, their prescription would be to get themself warmed up. Indeed, it’s from this idea of the four humors that the modern use of the term phlegmatic originated—if someone is described this way, it might be because they are rather cold and self-centered.
Too much yellow bile and someone was choleric or given to fits of anger. So if they had too much yellow bile, and thus they were dry and hot, the prescription might be to give them a cold bath, or make them sit out in the snow. In other words, the prescription might be the opposite of that given to a phlegmatic.
Again, it can be imagined that taking a person who is ill and immersing them in cold water is probably neither comfortable nor conducive to helping the immune system do its job. Also, there would probably be some bloodletting no matter what the person’s humor type, just because that was almost always the go-to to get their humors back into balance.
If someone had too much black bile, then they were melancholic or given to sadness. In order to cure them of this, laxatives would be the way to go. And again, probably more bloodletting.
The same idea or kind of approach applied to the twelve astrological signs. Aquarius was an air sign—not a water sign, as some might expect given the name—and Leo was a fire sign. If air and fire are put together, they burn hotter.
Learn more about how the Black Death transformed the world.
The Difference Between Astrology and Astronomy
The fields of astrology and astronomy, which are considered separate things today, were one and the same in the medieval world. Today astronomy is a science practiced by highly educated and extensively trained specialists like Neil deGrasse Tyson.
But astrology is usually performed by an underpaid copy editor who types up a very generalized horoscope prediction for each sign, and it then gets printed in the daily newspaper next to the crossword puzzle and advice columns.
Astronomy is science; astrology is, for lack of a better word, bunk.
Learn more about communities that survived the first wave.
Effects of the Planets
But this was not the belief in the Middle Ages. People had developed the ability to identify different planets and their orbits and to map the night sky, and it must have seemed impossible that something so mysterious, awe-inspiring, and yet observable by those who were trained to do so could not have an effect on the Earth.
Indeed, in the medieval educational system, one of the seven liberal arts was astronomy, and in the Middle Ages, astronomy included within it what is thought of today as astrology. A popular and useful scientific device in the medieval world that was used to calculate the positions of planets, the Sun, the Moon, and latitude was something known as the astrolabe.
Its origins go back to ancient Greece, but it was quite popular in the medieval world, and during the time of the plague, many scientists and scholars were consulting their astrolabes to try and get a handle on what was happening in the heavens.
And of course, different astrological signs are associated with certain assigned qualities, not unlike the idea of the four humors that were assigned to the human body.
Common Questions about the Absurd Sciences of the Medieval World
Based on the idea of the four humors, this absurd science suggested that if someone’s humors weren’t balanced—for example, in medieval medical terms, if they were too sanguine—their physician might actually perform bloodletting to try and bring their humors back into balance.
This absurd science was based on the theories of the Greek physician Galen. The theories suggested that the human body has four humors which should always be in balance so the body stays healthy. Any imbalance in the humors would cause illness in the body.
The fields of astrology and astronomy were one and the same in the medieval world. People could identify different planets and their orbits and map the night sky, and so it must have seemed impossible that something so mysterious yet observable could not have an effect on the Earth.