Between sentential and model-based abductions: a dialogical approach

Most of the standard approaches consider abduction in terms of a backward reasoning and miss some of its fundamental features. Overall, they neglect its pragmatic dimension and the conjectural aspect of the conclusion. In this paper, we approach abduction in terms of strategic adjustment process in the context of dialogical logic. This sheds light on the use of conjectures in argumentative interactions. Although abductive dialogues are sometimes based upon sentential conjectures, they can also involve hypotheses about the context of argumentation itself. Indeed, the underlying logic of an argumentative interaction is not always settled since the beginning. In this context, abduction is not only concerned with the introduction of sentential hypotheses, but also with hypotheses concerning the structural rules governing the dialogue itself. We thus emphasize the instrumental dimension of abduction in dialogues.