In this article, we first study abduction in human dialogues. Given an utterance, objective abduction produces a hearer’s belief that could explain the utterance, while subjective abduction produces a hearer’s belief that could explain the belief state of a speaker. Different types of abduction are formulated using propositional epistemic logic. We next consider conversational implicature used as pragmatic inference in speech acts. Two conflicting implicatures, Q-implicature and I-implicature, are formulated and contrasted with abduction. We also argue how speakers could use (...) abduction or conversational implicature for the purpose of misleading hearers. (shrink)

This work proposes an understanding of deductive, default and abductive reasoning as different instances of the same phenomenon: epistemic dynamics. It discusses the main intuitions behind each one of these reasoning processes, and suggest how they can be understood as different epistemic actions that modify an agent’s knowledge and/or beliefs in a different way, making formal the discussion with the use of the dynamic epistemic logic framework. The ideas in this paper put the studied processes under the same umbrella, thus (...) highlighting their relationship and allowing a better understanding of how they interact together. (shrink)

Abductive problems and their solutions are presented by means of justification logic. We introduce additional meta-constructions in order to generate and compare different solutions to the same abductive problem. Our approach has three advantages: (i) it makes structurally explicit the solution to an abductive problem (as it has a syntactic nature); (ii) it gives a precise meaning to the notion of evidence; (iii) it provides clear definitions and procedures for the comparison of solutions that can be adapted to different needs.