Abduction

Conceptual Overview and Discussion

In the late 1800s the founder of pragmatism and polymath, Charles Sanders Peirce, distinguished abduction as a third form of inference necessary for a more complete understanding of the processes of intelligent inquiry. Deduction, as the form of necessary reasoning from which we derive specific observations from generalizations, has dominated Western scientific thinking for over 2,000 years. Not quite as long lived, induction, as the form of probabilistic reasoning from which we derive generalizations from specific observations, has been a feature of modern science for some 700 years.

About a century ago, Peirce suggested that there is a broad class of reasoning that is neither deductive nor inductive but involves inferences from effects to causes. He pointed out that both deduction and induction are closed with reference to the concepts in play. Another form of reasoning was needed to generate new concepts; he came to call this form of reasoning abduction. Not to be confused with inference to the best explanation, which begins from already established hypotheses, abduction is the mode of inference aimed at developing new ideas. Its basic formula is

The surprising fact, C is observed:

As the presented formula for abduction indicates, it is an inherently transactional process and the element of surprise plays a critical role in stimulating it. The surprise may be relatively active, as when one makes an effort to anticipate a particular result that does not occur, or it may be passive, as when a situation presses itself on one's consciousness. When expectations fall short in some way, abduction is triggered. A central tenet of Peirce's epistemology is that all thinking behaviors, from perception to logical and mathematical reasoning, are mediated by signs. Consequently an observation's status as “fact” or as “surprising,” and as the impetus to abduction, is never given purely; it is always mediated by modes of perception, by background perspectives and theories. Its [Page 2]surprising character exists only with respect to certain expectations held under certain circumstances. Surprise signals a need and an opportunity to invent a new way of understanding.

Stimulated by surprise, abduction is involved when scientists struggle for new kinds of intelligible patterns in observations—that is, when they strive to generate a possible “A.” The struggle may involve many possible imaginative elements, including hunches, guesses, conjectures, associations, metaphors, speculations, propositions, models, and so on. Furthermore, abduction need not occur in the context of existing language because the formation of new explanations often goes hand in hand with the development of new or newly combined theoretical terms such as “quark,” “AIDS,” and “garbage can model of decision making.” As a form of reasoning, it is suppositional, suggesting only what “may be.” However, abduction's value and weakness are two sides of the same coin. It is weak in the sense that the “might be's” entertained are highly permissive; yet that very permissiveness is the source of inventiveness. What at first blush may seem irrelevant, just a loose notion or even nonsensical, may be the beginning of novel ways of understanding.

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