2020 年 37 巻 p. 21-38
Abduction is a mode of inference that Peirce focused on in his attempt to identify the way of scientific discovery. Deduction, on the other hand, is another mode of inference with a long history in Western philosophy. The difference between the two is that the former just offers a most likely (plausible) option out of possible alternatives while the latter always gives the true conclusion as long as the underlying assumptions are correct. In utterance interpretation, especially when we are interested in implied meaning (or implicature), an abductive process with its focus on hypothesis-formation is in order, because abduction is quite in line with implicature as the former is non-monotonic (i.e., with more than one conclusion) and the latter defeasible (i.e. can be cancelled). Being monotonic and non-defeasible, deduction in contrast is incompatible with implicature. Relevance theory, a pragmatic study of implicit meaning, however, depends heavily on DEDUCTIVE processes in trying to identify how implicature is produced and understood, although it obviously refers to ABDUCTIVE processes. This paper shows the widespread preference for deduction in Western literature including linguistics, and why abduction has long been ignored and even practically forgotten (to be replaced by deduction) in academic discussions.