We contend that it is possible to argue reasonably for and against arguments from classifications and definitions, provided they are seen as defeasible (subject to exceptions and critical questioning). Arguments from classification of the most common sorts are shown to be based on defeasible reasoning of various kinds represented by patterns of logical reasoning called defeasible argumentation schemes. We show how such schemes can be identified with heuristics, or short-cut solutions to a problem. We examine a variety of arguments of (...) this sort, including argument from abductive classification, argument from causal classification, argument from analogy-based classification and arguments from classification based on generalizations. (shrink)

This investigation uses the technique of the profile of dialogue as a tool for the evaluation of arguments from ignorance (also called lack-of-evidence arguments, negative evidence, ad ignorantiam arguments and ex silentio arguments). Such arguments have traditionally been classified as fallacies by the logic textbooks, but recent research has shown that in many cases they can be used reasonably. A profile of dialogue is a connected sequence of moves and countermoves in a conversational exchange of a type that is goal-directed (...) and can be represented in a normative model of dialogue. Selected case studies are used to probe special features of using the profile technique as applied to arguments from ignorance of a kind that occur frequently in everyday conversational exchanges. One of these special features is the use of Gricean implicature. Another is the need to use negative profiles of argument. (shrink)

tational background of dialectic: the structure of formal disputation. Formal disputation Perhaps the clearest, and surely historically the most prominent, ...

This book identifies 25 argumentation schemes for presumptive reasoning and matches a set of critical questions to each.

The notion of “the burden of proof” plays an important role in real-world argumentation contexts, in particular in law. It has also been given a central role in normative accounts of argumentation, and has been used to explain a range of classic argumentation fallacies. We argue that in law the goal is to make practical decisions whereas in critical discussion the goal is frequently simply to increase or decrease degree of belief in a proposition. In the latter case, it is (...) not necessarily important whether that degree of belief exceeds a particular threshold (e.g., ‘reasonable doubt’). We explore the consequences of this distinction for the role that the “burden of proof” has played in argumentation and in theories of fallacy. (shrink)

À quelles conditions peut-on, dans un discours réel, utiliser un énoncé comme argument en faveur d’un autre? La réponse semble aller de soi, au moins si l’on assimile l’argumentation à une espèce de raisonnement - peut-être lâche et flou, mais analogue en son fond à la démonstration étudiée par les logiciens. Dans ce cas, l’enchaînement des énoncés se fonde sur les informations qu’ils véhiculent, sur ce qu’ils disent de la réalité. C’est justement l’inverse que veut montrer la théorie des échelles (...) argumentatives. Selon elle, la structure des énoncés, au sens le plus étroitement grammatical du terme, contient, indépendamment des informations qu’ils donnent, des indications sur le type de conclusions qu’ils peuvent servir. Le sens même de nos paroles doit alors être vu comme étant, de façon intrinsèque, un moyen pour orienter le discours de l’autre, l’intention de dire ne se distinguant pas de l’intention de faire dire. Ce qui fait triompher le structuralisme là où on l’attend le moins, en sémantique - la valeur sémantique d’un énoncé est constituée par allusion à la possibilité d’un autre énoncé - l’énoncé de l’autre. (shrink)

blandior ratio : C, 34). I will first survey how extensive, albeit usually overlooked, is Leibniz’s concern with these “weaker” forms of reasoning, and how crucial they are for many of his practical and theoretical endeavors. I will then trace back this acute need of Leibniz´s brand of rationalism to the peculiar nature of the Principle of Sufficient Reason (PSR), as opposed to the other basic principle of his philosophy, the Principle of Contradiction (PC). I will present here only the (...) bare bones of the argument, in a sort of extended summary, omitting the textual support as well the references to the relevant secondary literature. (shrink)