Way back when in ancient Greece, a medical philosopher named Claudius Galen developed one of the first personality theories. Galen's theory of the four temperaments was based on the even more ancient idea that all humans had four humors, or bodily fluids, in them--blood, phlegm, black bile and yellow bile. (ok, so that's a little, uh... *GROSS*.)
Galen believed that the four humors produced different moods in people: melancholic--kind of sad (lotsa black bile), choleric--hot-tempered (lotsa yellow bile), phlegmatic--slow and deliberate (lotsa phlegm) and sanguine--warm and pleasant (lotsa blood). As with other personality systems (Chinese elements, ayurvedic types), the goal is to find a balance between these different aspects of your personality.
