Abstract

This chapter looks at deduction, induction, and retroduction, which are three forms of reasoning that explain observations or develop new explanations from observations, by connecting sentences to a logical structure. Deduction explains individual occurrences of a phenomenon based on general sentences (laws) and respective circumstances. Induction derives general sentences (laws) from repeated observations of similar events. Retroduction, also often referred to as ‘abduction’, is an educated guess about the likely explanation for an observation, which can then be tested. The purpose of applying these forms of reasoning to observational studies is to make logic an explicit tool that applies extant knowledge, or develops new knowledge. While deduction applies extant knowledge, induction and retroduction develop new knowledge. The basic structure of all three forms of reasoning is derived from classical syllogisms (arguments), i.e. a structure in language that combines sentences (premises) to a conclusion. The chapter then considers examples of scientific work that applies the three forms of reasoning.