Any analysis of a character's psychology can only be done with a clear understanding of humoral theory, as this is was the indicator of a person's physical and mental health according to medical practitioners during Webster's time. Although the theory of the four elements (the basis for the humoral theory) has been a long and far reaching history, the concept of translating that into medical terms is first credit to have been introduced by Hippocrates to Greek medicine. The theory held that a balance of the four main fluids in the body, phlegm, blood, yellow bile and black bile, which each carried a different personality trait, was responsible for the character and temperament of an individual. .

             According to A Dictionary of Public Health each of the four mentioned body fluids corresponds with a personality trait, phlegmatic, sanguine, choleric and melancholic respectively (). An individual may naturally be disposed to certain personality type, for instance a person may naturally portray choleric characteristics and yellow bile fluids may naturally be higher in his body than other fluids, the problem occurs when the alchemy or pre-established fluid levels are disrupted resulting in an imbalance. The Oxford Companion to the Body states that the imbalance may be caused by an access of fluids, an abnormality in fluid quality or if the fluid (humor) gets putrefied or becomes too hot. .

             The Oxford Dictionary of the Classical World contains an article titled Ecology (Greek and Roman), which adds that the four seasons has an impact on the four humors and that the change in weather prompted certain humors to prevail in certain people. According to the article the body fluid phlegm, which originates in the lungs, corresponds to the winter season and its attributes are cold and moist making water its element. A person naturally disposed to a phlegmatic personality is impassive, unemotional and stoic.