Resumen DeLP is a defeasible argumentation system that captures common sense reasoning features. Examples proposed in the literature show that DeLP gets counterintuitive results. We suggest a possible cause of this problem and we propose an approach to neutralize it. The approach is based on the pre-selection criterion of arguments, called maximal specificity. The criterion establishes that an argument will be considered like maximally specific only if, for every argument based on more specific evidence which does not explain the same (...) conclusion, it explains neither the contrary nor something more general. (shrink)

Formal arguments are often represented by pairs, but in this paper we consider normative arguments represented by sequences of triples, where constitutive norms derive institutional facts from brute facts, and regulative norms derive deontic facts like obligations and permissions from institutional facts. The institutional facts may be seen as the reasons explaining or warranting the deontic obligations and permissions, and therefore they can be attacked by other normative arguments too. We represent different aspects of normative reasoning by different kinds of (...) consistency checks among these triples, and we use formal argumentation theory to resolve conflicts among such normative arguments. In particular, we introduce various requirements for arguing about norms concerning violations, contrary-to-duty obligations, dilemmas, conflict resolution and different kinds of norms, and we introduce a formal argumentation theory satisfying the requirements. In order to illustrate our framework, we introduce a running example based on university regulations for prospective and actual students. (shrink)

We present a formal, mathematical model of argument structure and evaluation, taking seriously the procedural and dialogical aspects of argumentation. The model applies proof standards to determine the acceptability of statements on an issue-by-issue basis. The model uses different types of premises (ordinary premises, assumptions and exceptions) and information about the dialectical status of statements (stated, questioned, accepted or rejected) to allow the burden of proof to be allocated to the proponent or the respondent, as appropriate, for each premise separately. (...) Our approach allows the burden of proof for a premise to be assigned to a different party than the one who has the burden of proving the conclusion of the argument, and also to change the burden of proof or applicable proof standard as the dialogue progresses from stage to stage. Useful for modeling legal dialogues, the burden of production and burden of persuasion can be handled separately, with a different responsible party and applicable proof standard for each. Carneades enables critical questions of argumentation schemes to be modeled as additional premises, using premise types to capture the varying effect on the burden of proof of different kinds of questions. (shrink)

Johnson‐Laird and coworkers' Mental Model theory of propositional reasoning is shown to be somewhere in between what logicians have defined as “credulous” and “skeptical” with respect to the conclusions it draws on default reasoning problems. It is then argued that in situations where skeptical reasoning has been shown to lead to problematic conclusions due to not being skeptical enough, the bolder Mental Model theory will likewise make counterintuitive predictions. This claim is supported by the consideration of two of those situations, (...) namely problems involving reinstatement and floating conclusions. It is discussed how the recent “principle of pragmatic modulation” could be a first step in order to overcome the mild credulity of Mental Model reasoning. (shrink)

Reasoning with cases has been a primary focus of those working in AI and law who have attempted to model legal reasoning. In this paper we put forward a formal model of reasoning with cases which captures many of the insights from that previous work. We begin by stating our view of reasoning with cases as a process of constructing, evaluating and applying a theory. Central to our model is a view of the relationship between cases, rules based on cases, (...) and the social values which justify those rules. Having given our view of these relationships, we present our formal model of them, and explain how theories can be constructed, compared and evaluated. We then show how previous work can be described in terms of our model, and discuss extensions to the basic model to accommodate particular features of previous work. We conclude by identifying some directions for future work. (shrink)

This paper discusses the relation between deontic logic and the study of conversational interactions. Special attention is given to the notion of remedial interchange as analysed by sociologists and linguistic pragmaticians. This notion is close to the one of contrary-to-duty (reparational) obligation, which deontic logicians have been studying in its own right. The present article also investigates the question of whether some of the aspects of conversational interactions can fruitfully be described by using formal tools originally developed in the study (...) of iterated belief change. I here adapt the latter tools to deontic logic, and attempt an account of remedial interchange (and, more generally, contrary-to-duty reasoning) in terms of commutation. This account brings the dynamics of obligations to the fore. (shrink)

The aim of this paper is to strengthen the point made by Horty about the relationship between reason holism and moral particularism. In the literature prima facie obligations have been considered as the only source of reason holism. I strengthen Horty’s point in two ways. First, I show that contrary-to-duties provide another independent support for reason holism. Next I outline a formal theory that is able to capture these two sources of holism. While in simple settings the proposed account coincides (...) with Horty’s one, this is not true in more complicated or “realistic” settings in which more than two norms collide. My chosen formalism is so-called input/output logic. A bottom-line example is introduced. It raises the issue of whether the conventional wisdom is right in assuming that normative reasons run parallel to epistemic ones. (shrink)