Introduction to biomedical logic

Abstract Reasoning involves using the relationships among assertions to draw a true inference. The basic unit of reasoning is the syllogism, which takes the form: assuming assertion A and B are true, then we can conclude the assertion C is true. A logical argument involves chaining syllogisms to draw a new inference. Because syllogisms can be examined easily, they serve as an excellent model for uncovering faulty reasoning, and most books on logic contain dozens of examples of fallacious inferences drawn from deceptively constructed syllogisms. In this chapter, we will discuss common fallacies selected from the field of biomedicine. We will also discuss the concept of proof, as it is known to biologists, and how it differs from proof, as it is known to mathematicians. We will see that biologists can seldom prove anything, with certainty, but lacking such proof does not prohibit us from establishing physical laws and generalizations based on the relationships among observable biological processes.