Intuitions and the modelling of defeasible reasoning: some case studies

The purpose of this paper is to address some criticisms recently raised by John Horty in two articles against the validity of two commonly accepted defeasible reasoning patterns, viz. reinstatement and floating conclusions. I shall argue that Horty's counterexamples, although they significantly raise our understanding of these reasoning patterns, do not show their invalidity. Some of them reflect patterns which, if made explicit in the formalisation, avoid the unwanted inference without having to give up the criticised inference principles. Other examples seem to involve hidden assumptions about the specific problem which, if made explicit, are nothing but extra information that defeat the defeasible inference. These considerations will be put in a wider perspective by reflecting on the nature of defeasible reasoning principles as principles of justified acceptance rather than `real' logical inference.Comment: Proceedings of the 9th International Workshop on Non-Monotonic Reasoning (NMR'2002), Toulouse, France, April 19-21, 200

An Argumentation‐Based Analysis of the Simonshaven Case

In an argumentation approach, legal evidential reasoning is modeled as the construction and attack of “trees of inference” from evidence to conclusions by applying generalizations to evidence or intermediate conclusions. In this paper, an argumentation‐based analysis of the Simonshaven case is given in terms of a logical formalism for argumentation. The formalism combines abstract argumentation frameworks with accounts of the structure of arguments, of the ways they can be attacked and of ways to evaluate conflicting arguments. The purpose of this paper is not to demonstrate or argue that the argumentation approach to modeling legal evidential reasoning is feasible or even preferable but to have a fully worked‐out example that can be used in the comparison with alternative Bayesian or scenario‐based analyses