The world during the early Middle Ages was backward-looking.  Science as we understand it, with theory, experiment, and refinement, had not yet been considered.  The beliefs of the Greeks, which were based on pure thought instead of observation, dominated thinking instead.  Greek philosophy had long held that all objects in the universe were made up of four elements – Earth, Water, Fire, and Air.  A later thinker had realized that the human body should follow the same law.  He equated the elements to Black Bile, Phlegm, Yellow Bile, and Blood respectively.  Like the elements, each bodily humour was associated with the state of hot or cold and dry or wet.  The humours were later also associated with distinct organs, seasons, and even temperaments.

As applied to medicine, it gave the Medieval doctor a clear idea about health, diseases, and other maladies.  The body, so the theory held, had an optimal balance.  If a person was not in perfect health that was the symptom but the cause was an imbalance.  One’s illness, weaknesses, even personality were thought to be a direct result of his or her particular balance being disrupted.  Health could be restored by regaining balance.

Herbs were central for restoring a person’s that balance.  These were each considered to have their own elemental qualities.  One or more would be chosen with the properties the patient was lacking.  These would be prepared and then taken by ingestion or application to the skin.  Other approaches were also taken; bleeding a person, applying hot cups, emetics, and forcing purges were all common methods.

Medieval medicine was deeply flawed because it had no awareness of microscopic organisms or the various drugs the body produces naturally.  The best example for this unfortunate lack of understanding can be found during the Bubonic Plague.  It was believed that Arsenic in a poultice bag could cure the disease.