In this work, we question the ability of existing ranking-based semantics to capture persuasion settings, emphasising in particular the phenomena of procatalepsis and of fading. Some widely accepted principles of ranking-based semantics are incompatible with a faithful treatment of these phenomena, which means that no existing ranking-based semantics can capture these two principles together. This motivates us to introduce a new parametrized ranking-based semantics based on the notion of propagation which extends the existing propagation semantics 139–150) by adding an additional (...) parameter allowing us to gradually decrease the impact of arguments when the length of the path between two arguments increases. We show that this parameter gives the possibility of choosing if one wants to satisfy the property Void Precedence or not and to control the scope of the impact of the arguments. We also propose an experiment to show that the new semantics remains stable when this parameter varies and an axiomatic evaluation to compare it with existing ranking-based semantics in the literature. (shrink)

The purpose of this paper is to discuss some ways in which dialectical models can be put to computational use. In particular, we consider means of facilitating human-computer debate, means of catering for a wider range of dialogue types than purely debate and means of providing dialectical support for group dialogues. We also suggest how the computational use of dialectical theories may help to illuminate research issues in the field of dialectic itself.

1. Argumentation consists in reasoning with conflicting information based on the exchange and evaluation of interacting arguments. It can be used for modelling dialogue (persuasion, negotiation), d...

I take 'informal logic' to be the (descriptive and normative) study of 'real arguments'-arguments which are or have been used with the aim of convincing others of a point of view. I argue that the informal logic tradition thus conceived (i) lends strong support to something like Quine's view that our beliefs really support one another like the filaments in a spider's web--and thus that the traditional view that implication is an asymmetric relation is false; (ii) suggests that the classic (...) division of arguments into deductive and inductive has distorted our thinking about the evaluation of real arguments; and (iii) implies that naturalised epistemology is on the right track. (shrink)

As Russell's paradox of "the set of all sets that do not contain themselves" indicated long ago, matters go seriously amiss if one operates an ontology of unrestricted totalization. Some sort of restriction must be placed on such items as "the set of all sets that have the feature F' or "the conjunction of all truths that have the feature G." But generally, logicians here introduce such formalized and complex devices as the theory of types or the doctrine of impredictivity. (...) The present paper argues for the informal and elementary idea that the items invoked in a proper identification have themselves already been identified. Even as an explanation is not satisfactory that proceeds in terms of items that themselves require prior explanation, so the same holds with identification. And heed of this elementary idea suffices to sideline those otherwise paradoxical perplexities. (shrink)