Many philosophers set forth principles that can apply in medicine: Other things being equal, the simplest hypothesis possible is the good principle (Aristotle). Distinguish between two hypotheses, by shaving away unnecessary assumptions or cutting apart two similar conclusions; and the competing hypotheses with the fewest assumptions should be selected (Ockham). The obvious diagnosis is the most likely—when you hear hoof beats, think of horses not zebras (Woodward). Entities are not to be multiplied without necessity (Punch). We are to admit no more causes of natural things than are both true and sufficient to explain their appearances…to the same natural effects we must, as far as possible, assign the same causes. (Newton).

In more modern times, the philosophy of modern medicine has been: A man can have as many diseases as he damn well pleases (Hickam); and hiatus hernia, gallbladder disease, and diverticulosis are three different diseases, and even though the diseases may exist in a single patient they have no common cause (Saint).

Medicine has named 1,000’s of diseases and syndromes; and continues to expand the number of named diseases, based on descriptions of findings, symptoms and effects. Many diseases of unknown origin were described before medicine could identify infectious pathogens. Co-morbid diseases can have a common cause—infectious pathogens attacking in related anatomical locations. Diagnostic testing for immortal pathogens and parasites can identify root causes of chronic disease, and causes of co-morbid conditions. Simplification in naming and diagnosing disease, based on causes rather than findings, symptoms, and effects, will advance science.