The purpose of this paper is to show how micro-argumentation mechanisms of presumptive reasoning and reasoning from best explanation can be used for explaining some cases of presupposition cancellation. It will be shown how the relationship between presupposition triggers and pragmatic presuppositions can be analyzed in terms of presumptive and non-presumptive polyphonic articulation of an utterance, resulting in different types of commitments for the interlocutors. This approach is grounded on the two interconnected notions of presumptions and commitments. In some complex (...) cases of presupposition “suspension,” the speaker presumes the hearer’s acceptance of and commitment to propositions that cannot be presumed as such, namely that do not belong to the common ground, or that have been explicitly rejected as being commonly shared. This phenomenon triggers a complex type of reasoning that can be represented as an abductive pattern, grounded on hierarchies of presumptions and aimed at providing an interpretation that solves this conflict of presumptions. Several cases of suspension of presupposition will be investigated as resulting from non-presumptive polyphonic articulations, in which different voices responsible for distinct commitments are distinguished. By indirectly reporting an element of discourse, the speaker can refuse to take responsibility for the presupposed proposition, and correct the commitments that may result for him. This polyphonic treatment of utterances shows how and why a presupposition is suspended, and identifies the conflicting presumptions that can be further solved through reasoning from best explanation. This reasoning can result in a different reconstruction of the developed logical form of utterance or of its illocutionary force. (shrink)