Although Peirce states that abduction is the “only logical operation which introduces any new idea,” many, if not most, explanatory hypotheses offer nothing new at all. They do not seem to be, in the sense Peirce means, abductively derived. In various writings, Peirce provides at least four different descriptions of abduction. Italian computational philosopher Lorenzo Magnani proposes three types of abduction: theoretical, model-based, and creative (the final chapter of this book discusses the third type). In her 2005 paper for Semiotica (“Abduction as an Aspect of Retroduction”), Chiasson points out that Peirce uses two distinct and contradictory terms to signify these processes. The purpose of this chapter is to clarify the various ways abduction has been defined. In addition to defining abduction as an aspect of retroduction, the authors discuss induction, with which abduction is often confounded. This discussion of induction includes the concepts diagnosis and inference to the best explanation, both of which can be achieved inductively (and deductively as well, though deduction will not be addressed here), as well as abductively.
