In discussions about reasoning in medical research and practice, we often encounter the label "the logic of medicine". There are those who believe that medicine has indeed a logic of its own like, for example, quantum mechanics supposedly rests upon a so-called "quantum logic" in which the Distributive Laws of classical logic, listed in Table 37 on page 898, are not valid (Birkhoff and von Neumann 1936; Dalla Chiara and Giuntini , 2002). Several special treatises have also been published under the metaphoric title "the logic of medicine" (Blane , 1819; Bieganski , 1909; Oesterlen , 1852; Murphy , 1997). They use the word "logic" not in the strict sense of this term, but with a loose meaning related with the analysis of medical concepts, ideas, hypotheses, theories, methods, and decisions. They do not reveal whether medicine has its own specific, "logic". To determine whether there is such a logic of medicine or not, we shall first clarify what is meant by the term "logic". We shall then introduce some auxiliary notions to aid us in answering our question.