Presumptions, and How They Relate to Arguments from Ignorance

By explaining the argument from ignorance in terms of the presumption of innocence, many textbooks in argumentation theory suggest that some arguments from ignorance might share essential features with some types of presumptive reasoning. The stronger version of this view, suggesting that arguments from ignorance and presumptive reasoning are almost indistinguishable, is occasionally proposed by Douglas Walton. This paper explores the nature and limits of the stronger proposal and argues that initial presumptions and arguments from ignorance are not closely connected. There are three main reasons. First, the argument from ignorance, unlike typical presumptive reasoning, is a negative kind of inference. Second, the typical initial presumption is sensitive to a broader set of defeaters and thus assumes a higher (negative) standard of acceptability. Third, in dialectical terms, initial presumption and argument from ignorance bring different attacking rights and obligations. I conclude that Waltonian intuition is unsupported or, at best, is limited only to practical presumptions and practical arguments from ignorance.

A dialectical approach to presupposition

This paper advances an approach to presupposition rooted in the concept of commitment, a dialectical notion weaker than truth and belief. It investigates ancient medieval dialectical theories and develops the insights thereof for analyzing how presuppositions are evaluated and why a proposition is presupposed. In particular, at a pragmatic level, presuppositions are reconstructed as the conclusions of implicit arguments from presumptive reasoning, grounded on presumptions of different type and nature. A false (or rather unaccepted) presupposition can be thus represented as the outcome of a conflict of presumptions – the ones used by the speaker and the ones commonly accepted or backed by evidence. From an interpretative perspective, this defaulted presumptive reasoning can be explained by comparing the available presumptions and repaired by replacing the weaker and unacceptable ones.

Evidence and presumptions for analyzing and detecting misunderstandings

The detection and analysis of misunderstandings are crucial aspects of discourse analysis, and presuppose a twofold investigation of their structure. First, misunderstandings need to be identified and, more importantly, justified. For this reason, a classification of the types and force of evidence of a misunderstanding is needed. Second, misunderstandings reveal differences in the interlocutors’ interpretations of an utterance, which can be examined by considering the presumptions that they use in their interpretation. This paper proposes a functional approach to misunderstandings grounded on presumptive reasoning and types of presumptions, in which incompatible interpretations or interpretative failures are examined as defaults of the underlying interpretative reasoning, caused by overlooked evidence or conflicting presumptions. Moreover, it advances a classification of the types and the probative weights of the evidence that can be used to detect misunderstandings. The proposed methodology and its implications are illustrated through the analysis of doctor–patient communication in diabetes care.

Understanding misunderstandings. Presuppositions and presumptions in doctor-patient chronic care consultations

Pragmatic presupposition is analyzed as grounded on an implicit reasoning process based on a set of presumptions, which can define cultural differences. The basic condition for presupposing a proposition is represented as a reasoning criterion, namely reasonableness. Presuppositions, on this view, need to be reasonable, namely they need to be the reasonable conclusions of an underlying presumptive reasoning, which does not or may not contain contradictions with other presumptions. Presumptions are in turn analyzed considering their nature and their hierarchy, namely their subject matter and their possible contextual backing, which eliminates some of their possible defaults. This analysis of presupposition brings to light the relationship between misunderstandings deriving from presuppositional failures and the underlying system of presumptions. This approach is applied to the investigation of communicative issues within the medical context, and more precisely doctor-patient communication in diabetes cases.

Uncommon ground

The purpose of this paper is to show how microargumentation mechanisms of presumptive reasoning and reasoning from best explanation can be used to explain some cases of presupposition suspension. It will be shown how the relationship between presupposition triggers and pragmatic presuppositions can be analyzed in terms of presumptive and nonpresumptive 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 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 kind of abduction, grounded on hierarchies of presumptions and aimed at providing an interpretation that solves this conflict of presumptions. Several cases of presupposition suspension will be shown to result from nonpresumptive 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 or her. This polyphonic treatment of utterances can explain how and why a presupposition is suspended, and can be used to identify 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 or the illocutionary force of an utterance.

Analogical reasoning in public health

Analogical reasoning is a valuable logical resource in a public health context. It is used extensively by public health scientists in risk assessments of new technologies, environmental hazards and infectious diseases. For its part, the public also avails of analogical reasoning when it assesses a range of public health problems. In this article, some of these uses of analogical reasoning in public health are examined. Analogical arguments have courted approval and disapproval in roughly equal measure by a long succession of logicians and philosophers. The logical features of these arguments which make them simultaneously compelling and contemptible are considered. As a form of presumptive reasoning, analogical arguments have a valuable role to play in closing epistemic gaps in knowledge. This heuristic function of these arguments is illustrated through an examination of some uses of analogical reasoning in recent public health crises. Finally, the results of a study of analogical reasoning in 879 members of the public are reported. This study reveals that lay members of the public are able to discern the logical and epistemic conditions under which analogical arguments are rationally warranted in a public health context.

The Dialogical Force of Implicit Premises. Presumptions in Enthymemes.

The implicit dimension of enthymemes is investigated from a pragmatic perspective to show why a premise can be left unexpressed, and how it can be used strategically. The relationship between the implicit act of taking for granted and the pattern of presumptive reasoning is shown to be the cornerstone of kairos and the fallacy of straw man. By taking a proposition for granted, the speaker shifts the burden of proving its un-acceptability onto the hearer. The resemblance (likeliness) of the tacit premise with what is commonly acceptable or has been actually stated can be used as a rhetorical strategy.