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Who came up with this idea? - Greek physician Hippocrates (c. 460 – c. 375 BCE) was the first to document the concept of the four humors. However its origins might date back to Ancient Egypt or Mesopotamia.

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How did it spread? - The concept was further disseminated by Galen (129–201 CE), a Greek physician and philosopher in the Roman Empire.

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Humorism - Humorism, or humoralism, was a system used in classical Greek medicine. It was based on the idea that we have four humors and that they should all be balanced.

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Humorism - Each of these four humors are linked to four fluids in the human body.

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What are the four humors? - The four humors in the human body are black bile, yellow bile, blood, and phlegm.

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Imbalance - Imbalance of these body fluids was believed to be the cause of a number of diseases and mental disorders.

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Qualities of humors - The four humors also have different qualities: hot, cold, wet, and dry. Each humor has a combination of these qualities.

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Combos - Blood is hot and wet, black bile is cold and dry, yellow bile is hot and dry, and phlegm is cold and wet.

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Psychological effects of the humors - The Greeks also believed that the four humors affected personality, and each would represent a temperament.

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Emotional characteristics - The four humors were linked to the following temperaments : sanguine (blood), melancholic (black bile), choleric (yellow bile), and phlegmatic (phlegm).

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Blood - A sanguine temperament meant that someone was social, outgoing, and courageous. So "too much" blood could make a person manic.

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Black bile - A melancholic temperament represented gloomy and despondent people. Excess black bile was associated with symptoms of depression.

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Yellow bile - Choleric people were essentially bad-tempered and aggressive, yet decisive and ambitious. These were usually dominant leaders.

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Phlegm - Phlegmatic individuals were calm, easy-going, and sometimes unemotional. Excess phlegm was linked to apathetic behavior.

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Four elements - The ancient Greeks linked the four humors to the four elements. Blood is air, black bile is earth, yellow bile is fire, and phlegm is water.

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The four seasons - They've also associated them with the four seasons. Blood (spring), black bile (fall), yellow bile (summer) , and phlegm (winter).

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Four stages of life - The four humors were also associated with different age stages in life. Blood (infancy), black bile (adulthood), yellow bile (youth), and phlegm (old age).

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What we can learn from the four humors - It’s all about balance, and continues to be so. Despite medical advances, balance in life can do wonders for one’s mental health.

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Health - The Greeks believed that in order to be healthy, the four humors should be balanced. Harmony was key to an individual’s well-being.

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Balance - A balanced diet and a good work-life balance are just some examples on how we can "balance our humors" and live healthier, happier lives.

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Balance in medicine - Ayurveda, Unani Tibb, and Traditional Chinese Medicine, all promote the idea of balance.

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Health - "Dyscrasia" was the term used when a person's humors were unbalanced. It essentially means "bad mixture."

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It was focused on the individual - The model was heavily focused on the individual, as everyone was unique in how their four humors manifested.

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Treatments - While someone diagnosed with too much blood could be prescribed bloodletting (where "excess" blood would be withdrawn), treatments for these imbalances were often more harmless.

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Treatments - If one or more of the humors was out of balance, Greek physicians would look into lifestyle changes, including diet and occupation.

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Similar model - Ayurveda (traditional Indian medicine) also developed a theory of humors, which was linked to the five Hindu elements.

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Legacy - Humorism was later adapted by Roman, Islamic, Perso-Arabic, and Indian medicine.

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Legacy - William Shakespeare has made reference to humorism in his plays. 

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Legacy -

The model was present in Western medicine until the 19th century.

See also: Strange and surprising psychological facts

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