The Conundrums of Psychology by Sam Vaknin

The study of psychopathology challenges modern views on health and illness by questioning the very definitions of sickness.

Excerpt:

We are all terminally ill, bound by the inevitable march of time toward aging and death. These processes remain deeply mysterious, evoking both awe and discomfort. Illness, by definition, contains a subjective element: "dis-ease." For any condition to be considered a disease, the individual must feel bad, experiencing discomfort. To this extent, all diseases can be seen as spiritual or mental. Is there an objective way to distinguish health from sickness that doesn’t rely on the patient's subjective experience?