Physicians are enjoined routinely to treat the patient, not the disease. It is then of some importance, or at least of interest, to know what it is that they are not to treat. Disease is a term in need of definition.
When Socrates insisted that his debaters define their terms, he gave them considerable latitude. Since there were no dictionaries at the time, a debater was on his own, and, much like Humpty Dumpty in Alice Through the Looking Glass, he could make words mean what he wanted them to mean. Lacking such latitude, we can take license with definitions only when, because of incompleteness or ambiguity, dictionaries leave a semantic void. This is the case with the word "disease."
Nor can dictionaries be faulted for such semantic inadequacy. Concepts of disease have varied through the centuries. Diseases have been conceived of as demonic possessions, divine punishments or trials, independently