It also includes medical ethics, medical metaethics, and medical law. Medical logic Publications entitled "The Logic of Medicine" give rise to the question whether medicine has its own logic like quantum logic is argued to be the logic of quantum mechanics. To answer the question, Sadegh-Zadeh distinguishes between logic in medicine and logic of medicine. "Logic in medicine" means the class of all logics that are, or may be, applied in medicine to solve theoretical or practical problems. Examples are classical two-valued logic, many-valued logic, paraconsistent logic, deontic logic, temporal logic, probability logic, fuzzy logic, and so on. Their number is unlimited. But none of them is specifically made for medical use. This logical pluralism in medicine parallels the mathematical pluralism in that innumerable mathematical theories are used in medicine as well without any of them being "the mathematics of medicine". So, there is no logic of medicine, Sadegh-Zadeh concludes, a logic that could be viewed or used as a specifically medical logic. Medical metaphysics Medical metaphysics is primarily concerned with (i) medical ontology, (ii) medical truth, and (iii) the nature of medicine. (i) Medical ontology. Sadegh-Zadeh devotes himself extensively to pure, formal, and applied ontology to use them in his logical analysis of medical-ontological issues of medical knowledge, clinical practice, nosology, psychiatry, psychosomatics, and biomedicine such as, for example, whether diseases exist or are fictitious entities invented by nosologists and physicians, and whether particular other things such as genes, psyche, and schizophrenia exist or are mere myths. To settle these enduring controversies and similar ones in medicine, he first distinguishes between ontology de re and ontology de dicto. The distinction is based on a syntactic criterion similar to Barcan formula and enables differentiation between fictional entities such as Sherlock Holmes and real ones. Second, he inaugurates an intriguing fuzzy ontology by introducing a many-place existence operator and fuzzyfying this operator to obtain a quantitative concept of existence that he calls the Heraclitean operator. The Heraclitean operator ranges over the domain of all imaginable entities, including existent, non-existent, and fictitious ones, and over all possible frames of reference, a frame of reference being a particular language and a particular logic. As a result, an entity exists, does not exist, or is fictitious only to a particular extent in the unit interval [0, 1] with respect to a particular language and a particular logic. In this way, ontological stances such as