Abductive Reasoning.

• Author: Lyne, John
• Position: Book review

Abductive Reasoning. By Douglas Walton. Tuscaloosa: University of Alabama Press, 2005; pp. xv + 320. $40.00 cloth.

Douglas Walton adds another volume to his extensive work on argumentation and informal reasoning. The theme of abduction, like the theme of "relevance" that was the focus of his previous volume, opens a territory of indeterminate dimensions. In fact, as the examples proliferate, it starts to look as if abduction is a very common form of reasoning. Walton's survey includes references to abduction in the natural sciences, but he is concerned primarily with its use in informal reasoning and in relation to explanation and understanding. Examining aspects of its role in the practices of law, medicine, artificial intelligence, and everyday argumentation, he also has relocated abduction within a dialogical framework.

The term itself, and one of the received theories of abduction, comes from the American pragmatist, Charles Sanders Peirce. For Peirce, the first modern logician to take seriously the prospect of a rhetoric of science, the concept was closely associated with the openness of scientific inquiry. Each fundamental form of reasoning--deduction, induction, and abduction--was described as dealing differently with relationships among the terms rule, case, and result within a syllogistic format. Abduction concerns the venturing of hypotheses and thus can tell us only what may be the case. Peirce said that we are reasoning abductively when we find ourselves considering some "curious circumstance" (135) and adopt a supposition which, if true, would account for it. Many of Sherlock Holmes' famously brilliant deductions were actually abductions in just this sense.

Subsequent philosophers of science have taken up this theme under the rubric of "inference to the best explanation," where an inference is made from given data to a hypothesis that would explain the data, and no better explanation can be found. But what respect do we owe to arguments that are only plausible? A hypothesis is at best only plausible, and the act of positing a plausible explanation is not governed by logic in any strict sense of the term. Indeed, many of the examples of abduction in Walton's book would be good candidates for informal fallacies, depending on the context. So for abduction, as is ever the case with practical reasoning, we need a theoretical understanding that lets us off the hook of deductive certitude without abandoning critical standards...