Presumptions in argumentation:a systematic analysis

Take some statement p that is objectively uncontroversial (e.g., “The Earth is globe-shaped”), and that you accept for that reason. Suppose, however, that your interlocutor is not convinced: she remains sceptical, or advances non-p. How should a reasonable discussion about p be structured? Should you (and only you) have the burden of proof and provide reasons, despite p’s objective plausibility? Should the burden allocation be symmetrical? Or should only those who reject plausible positions carry probative obligations? This dissertation studies the latter proposal. Some philosophers, legal scholars, argumentation theorists, and rhetoricians have argued that there is a set of dialectically privileged propositions, i.e., ‘presumptions,’ that asymmetrically allocate the burden(s) of proof. I analyse this ‘deontic function’ in connection to: presumption’s other functions (such as harm reduction and enabling dialogical progress), defeating conditions, the argument from ignorance, and justificatory strength. In general, I argue that the standard accounts of ‘deontic function’ require revisions and qualifications. In particular, I show that presumption entails distinct pragmatic, deontic, and dialogical functions, different defeating conditions, and distinct conceptions of justificatory strength—depending on whether the presumption is ‘practical’ (e.g., “We should proceed as if it will rain and bring an umbrella (although this is not certain)”) or ‘cognitive’ (e.g., “The Earth is globe-shaped”)