Bart Verheij

About the logical relations between cases and rules

The two main types of law are legislation and precedents. Both types have a corresponding reasoning pattern determining legal consequences: legislation can be applied and precedents followed. The separate modelling of these two reasoning patterns using logical techniques has recently seen considerable progress. About the logical links between the two less is known, although progress has already been made. This document focuses on such logical relations. The main question is: to what extent can the application of legislation and precedent adherence be considered as two sides of the same logical coin? Findings from the boundaries of logic and law will serve as a starting point. This text is a translated, adapted and extended version of Verheij 2007.

Dialectical argumentation with argumentation schemes: an approach to legal logic

This paper describes an approach to legal logic based on the formal analysis of argumentation schemes. Argumentation schemes a notion borrowed from the .eld of argumentation theory - are a kind of generalized rules of inference, in the sense that they express that given certain premises a particular conclusion can be drawn. However, argumentation schemes need not concern strict, abstract, necessarily valid patterns of reasoning, but can be defeasible, concrete and contingently valid, i.e., valid in certain contexts or under certain circumstances. A method is presented to analyze argumentation schemes and it is shown how argumentation schemes can be embedded in a formal model of dialectical argumentation.

Artificial argument assistants for defeasible argumentation

The present paper discusses experimental argument assistance tools. In contrast with automated reasoning tools, the objective is not to replace reasoning, but to guide the users production of arguments. Two systems are presented, ARGUE! and ARGUMED based on DEFLOG. The focus is on defeasible argumentation with an eye on the law. Argument assistants for defeasible argumentation naturally correspond to a view of the application of law as dialectical theory construction. The experiments provide insights into the design of argument assistants, and show the pros and cons of different ways of representing argumentative data. The development of the argumentation theories underlying the systems has culminated in the logical system DEFLOG that formalizes the interpretation of prima facie justified assumptions. DEFLOG introduces an innovative use of conditionals expressing support and attack. This allows the expression of warrants for support and attack, making it a transparent and flexible system of defeasible argumentation.

DefLog: on the logical interpretation of prima facie justified assumptions

Assumptions are often not considered to be definitely true, but only as prima facie justified. When an assumption is prima facie justified, there can for instance be a reason against it, by which the assumption is not actually justified. The assumption is then said to be defeated. This requires a revision of the standard conception of logical interpretation of sets of assumptions in terms of their models. Whereas in the models of a set of assumptions, all assumptions are taken to be true, an interpretation of prima facie justified assumptions must distinguish between the assumptions that are actually justified in the interpretation and those that are defeated. In the present paper, the logical interpretation of prima facie justified assumptions is investigated. The central notion is that of a dialectical interpretation of a set of assumptions. The basic idea is that a prima facie justified assumption is not actually justified, but defeated when its so-called dialectical negation is justified. The properties of dialectical interpretation are analysed by considering partial dialectical interpretations, or stages, and by establishing the notion of dialectical justification. The latter leads to a characterization of the existence and multiplicity of the dialectical interpretations of a set of assumptions. Since dialectical interpretations are a variant of stable semantics, the results are relevant for existing work on nonmonotonic logic and defeasible reasoning, on which the present work builds. Instead of focusing on defeasible rules or arguments, the present approach is sentence-based. A particular innovation is the use of a conditional that is prima facie justified (just like other assumptions) instead of an inconclusive conditional.

A hybrid formal theory of arguments, stories and criminal evidence

This paper presents a theory of reasoning with evidence in order to determine the facts in a criminal case. The focus is on the process of proof, in which the facts of the case are determined, rather than on related legal issues, such as the admissibility of evidence. In the literature, two approaches to reasoning with evidence can be distinguished, one argument-based and one story-based. In an argument-based approach to reasoning with evidence, the reasons for and against the occurrence of an event, e.g., based on witness testimony, are central. In a story-based approach, evidence is evaluated and interpreted from the perspective of the factual stories as they may have occurred in a case, e.g., as they are defended by the prosecution. In this paper, we argue that both arguments and narratives are relevant and useful in the reasoning with and interpretation of evidence. Therefore, a hybrid approach is proposed and formally developed, doing justice to both the argument-based and the narrative-based perspective. By the formalization of the theory and the associated graphical representations, our proposal is the basis for the design of software developed as a tool to make sense of the evidence in complex cases.

An Integrated View on Rules and Principles

In the law, it is generally acknowledged that there are intuitive differences between reasoning with rules and reasoning with principles. For instance, a rule seems to lead directly to its conclusion if its condition is satisfied, while a principle seems to lead merely to a reason for its conclusion. However, the implications of these intuitive differences for the logical status of rules and principles remain controversial.A radical opinion has been put forward by Dworkin (1978). The intuitive differences led him to argue for a strict logical distinction between rules and principles. Ever since, there has been a controversy whether the intuitive differences between rules and principles require a strict logical distinction between the two. For instance, Soeteman (1991) disagrees with Dworkins opinion, and argues that rules and principles cannot be strictly distinguished, and do not have a different logical structure.In this paper, we claim that the differences between rules and principles are merely a matter of degree. We give an integrated view on rules and principles in which rules and principles have the same logical structure, but different behavior in reasoning. In this view, both rules and principles are considered to consist of a condition and a conclusion. The observed differences between rules and principles are, in our view, the result of different types of relations that they have with other rules and principles. In the integrated view, typical rules and typical principles are the extremes of a spectrum.We support our claim by giving an explicit formalization of our integrated view using the recently developed formal tools provided by Reason-Based Logic. As an application of our view on rules and principles, we give three ways of reconstructing reasoning by analogy.

Arguing on the Toulmin Model

As my book The Uses of Argument pointed out, we must look and see how our critical standards vary from one area or activity to another—e.g. from politics to aesthetics. Hence we need to explore how these critical standards evolve, and how the most reflective and best-informed people in any area of experience refine those standards. We cannot understand where we are now unless we understand how we got here, even in a field like mathematics. Hence we must modestly recognize that the best we can do now is the best we can do now; and that those who come after us will move beyond our ideas. There is much contingency in these historical developments.

The law as a dynamic interconnected system of states of affairs: a legal top ontology

Abstract In this paper, an abstract model of the law is presented that has three primitives: states of affairs, events and rules. The starting point of the abstract model is that the law is a dynamic system of states of affairs which are connected by means of rules and events. The abstract model can be regarded as a top ontology of the law, that can be applied to legal knowledge representation. After an elaboration of the three primitives, the uses of the abstract model are illustrated by the analysis of central topics of law. Then we discuss heuristic guidelines for legal knowledge representation that are suggested by the abstract model. The paper concludes with a comparison with related work. The appendix contains a formalism for the abstract model.

Decision Support for Practical Reasoning A Theoretical and Computational Perspective

This book represents the first coherent published work in bringing together various branches of artificial intelligence with argumentation and rhetoric, and, as such, aims to play a key role in the establishment of a new field of scholarly research. The volume not only offers in-depth assessments of existing research, but also represents a substantial advance in the state of the art, and lays out a roadmap for future work in this newly emerging cross-disciplinary field. Audience: This book is of interest to academics, researchers, PhD and graduate students in philosophy of argument, logic, informal logic, critical thinking, rhetoric, artificial intelligence, multi-agent systems, computational linguistics, natural language processing, law, cognitive science and the interdisciplinary areas between these fields.Practical reasoning is reasoning about what is to be done. A decision on what to do may involve weighing the options open to an individual, taking into account dependencies on the actions of others, or complex collaborative decisionmaking. The role of argument in practical reasoning is explored in this chapter, both from a philosophical and computational perspective. In doing so, we discuss the use of computational systems in assisting people engaged in decision making, and, in particular, we investigate practical reasoning as joint deliberation between the human and decision support system. Such a system, it is argued, facilitates research into the use of argumentation techniques in computational models of practical reasoning, and the use of computational models to evaluate theories of practical reasoning.

Formalising argumentative story-based analysis of evidence

In the present paper, we provide a formalised version of a merged argumentative and story-based approach towards the analysis of evidence. As an application, we are able to show how our approach sheds new light on inference to the best explanation with case evidence. More specifically, it will be clarified how the events in a case story that are considered to be proven abductively explain the otherwise unproven events of the case story. We compare our approach with existing AI work on modelling legal reasoning with evidence.