Argumentation Schemes for Presumptive Reasoning

Argumentation Schemes for Presumptive Reasoning

Argumentation Schemes for Presumptive Reasoning

Argumentation Schemes for Presumptive Reasoning


Recent concerns with the evaluation of argumentation in informal logic and speech communication center around nondemonstrative arguments that lead to tentative or defeasible conclusions based on a balance of considerations. Such arguments do not appear to have structures of the kind traditionally identified with deductive and inductive reasoning, but are extremely common and are often called "plausible" or "presumptive," meaning that they are only provisionally acceptable even when they are correct. How is one to judge, by some clearly defined standard, whether such arguments are correct or not in a given instance? The answer lies in what are called argumentation schemes -- forms of argument (structures of inference) that enable one to identify and evaluate common types of argumentation in everyday discourse. This book identifies 25 argumentation schemes for presumptive reasoning and matches a set of critical questions to each. These two elements -- the scheme and the questions -- are then used to evaluate a given argument in a particular case in relation to a context of dialogue in which the argument occurred. In recent writings on argumentation, there is a good deal of stress placed on how important argumentation schemes are in any attempt to evaluate common arguments in everyday reasoning as correct or fallacious, acceptable or questionable. However, the problem is that the literature thus far has not produced a precise and user-friendly enough analysis of the structures of the argumentation schemes themselves, nor have any of the documented accounts been as helpful, accessible, or systematic as they could be, especially in relation to presumptive reasoning. This book solves the problem by presenting the most common presumptive schemes in an orderly and clear way that makes them explicit and useful as precisely defined structures. As such, it will be an indispensable tool for researchers, students, and teachers in the areas of critical thinking, argumentation, speech communication, informal logic, and discourse analysis.


In this chapter, a pragmatic analysis of the concept of presumption is put forward that reveals the essential function and operation of presumption in argumentation. The focus of the chapter is on presumptive reasoning, on how presumptions are brought forward in arguments as kinds of premises, and as kinds of inferences that link premises to conclusions in a context of argumentative dialogue.

Consider, for example, a very ordinary example of presumptive reasoning.

Case 2.1: John's hat is not on the peg. Therefore, John has left the house.

This inference is warranted by an unexpressed premise, a nonexplicit presumption that functions as a major premise of a conditional form: If John's hat is not on the peg, then (we can normally expect), he has left the house. The argumentation scheme is that of argument from sign, a species of defeasible inference subject to rebuttal in the presence of any contrary relevant evidence that becomes available (see chapter 3). Most likely, this conditional would be based (in a given case) on experience that John normally, or by habit, wears his hat whenever he leaves the house.

In Case 2.1, the key premise is a presumption that is not explicitly stated-- the proposition that John normally wears his hat when he leaves the house. This nonexplicit presumption licences the speaker, and any hearer, to draw the conclusion explicitly stated by the speaker--John has left the house.

Thus in this case, presumptive reasoning works as an inference through which a conclusion is drawn. But the case reveals an important distinction between explicit and nonexplicit presumptions. In the case of nonexplicit presumptions, they come to be accepted by the parties in the discussion, even though they may never be explicitly stated by any one of these parties during the discussion. The digging out of such presumptions has often been regarded as an important function of philosophy as a discipline.

In this case, the kind of inference involved is better described as implicature rather than implication, in the sense of conversational implicature described by Grice (1975). The conclusion is defeasibly drawn rather than being strictly implied by the premises.

Although presumptive reasoning is very important in philosophy, it has tended to be neglected by logicians. Although philosophers are familiar with . . .

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