This paper studies the modelling of legal reasoning about evidence within general theories of defeasible reasoning and argumentation. In particular, Wigmore's method for charting evidence and its use by modern legal evidence scholars is studied in order to give a formal underpinning in terms of logics for defeasible argumentation. Two notions turn out to be crucial, viz. argumentation schemes and empirical generalisations.

The main idea or the concept of coherence can be expressed in the following way: The more the statements belonging to a given theory approximate a perfect supportive structure, the more coherent the theory. The degree of perfection of a supportive structure depends on the degree to which the following criteria of coherence are fulfilled: (1) the greatest possible number of supported statements belonging to the theory in question; (2) the greatest possible length of chains of reasons belonging to it; (...) (3) the greatest possible number of strongly supported statements belonging to the theory; (4) the greatest possible number of connections between various supportive chains belonging to the theory; (5) the greatest possible number of preference relations between various principles belonging to it; (6) the greatest possible number and complexity of reciprocal supportive relations between various statements belonging to the theory; (7) the greatest possible number of universal statements belonging to the theory; the greatest possible number of general concepts belonging to it; the highest possible degree of generality of concepts implemented within it; the greatest possible number of resemblances between concepts used within it; (8) the greatest possible number of conceptual cross‐connections between various theories; (9) the greatest possible number of cases covered by the theory; and (10) the greatest possible number of fields of life covered by the theory. (shrink)

An abstract framework for structured arguments is presented, which instantiates Dung's ('On the Acceptability of Arguments and its Fundamental Role in Nonmonotonic Reasoning, Logic Programming, and n- Person Games', Artificial Intelligence , 77, 321-357) abstract argumentation frameworks. Arguments are defined as inference trees formed by applying two kinds of inference rules: strict and defeasible rules. This naturally leads to three ways of attacking an argument: attacking a premise, attacking a conclusion and attacking an inference. To resolve such attacks, preferences may (...) be used, which leads to three corresponding kinds of defeat: undermining, rebutting and undercutting defeats. The nature of the inference rules, the structure of the logical language on which they operate and the origin of the preferences are, apart from some basic assumptions, left unspecified. The resulting framework integrates work of Pollock, Vreeswijk and others on the structure of arguments and the nature of defeat and extends it in several respects. Various rationality postulates are proved to be satisfied by the framework, and several existing approaches are proved to be a special case of the framework, including assumption-based argumentation and DefLog. (shrink)

Inspired by legal reasoning, this paper presents a formal framework for assessing conflicting arguments. Its use is illustrated with applications to realistic legal examples, and the potential for implementation is discussed. The framework has the form of a logical system for defeasible argumentation. Its language, which is of a logic-programming-like nature, has both weak and explicit negation, and conflicts between arguments are decided with the help of priorities on the rules. An important feature of the system is that these priorities (...) are not fixed, but are themselves defeasibly derived as conclusions within the system. Thus debates on the choice between conflicting arguments can also be modelled.The proof theory of the system is stated in dialectical style, where a proof takes the form of a dialogue between a proponent and an opponent of an argument. An argument is shown to be justified if the proponent can make the opponent run out of moves in whatever way the opponent attacks. Despite this dialectical form, the system reflects a declarative, or relational approach to modelling legal argument. A basic assumption of this paper is that this approach complements two other lines of research in AI and Law, investigations of precedent-based reasoning and the development of procedural, or dialectical models of legal argument. (shrink)

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. (shrink)

This paper deals with the questions of whether the law should be coherent and what this coherence would amount to. In this connection so‐called “integrated coherentism” is introduced. According to integrated coherentism, an acceptance set is coherent if and only if it contains everything that should rationally be accepted according to what else one accepts and does not contain anything that should rationally be rejected according to what else one accepts. Such an acceptance set is ideally a theory of everything, (...) including amongst others standards for rational aceptance. On the assumption that the law, as a social phenomenon, is what the best theory about the law says it is, the law must be coherent, because the best theory of the law is part of an integratedly coherent theory of everything. This view is compatible with Raz's view that the law stems from different sources that need not be coherent in the sense that they consistently elaborate the same underlying principles or policies. Raz's view is not a consequence of integrated coherentism, however. (shrink)

This paper studies the modelling of legal reasoning about evidence within general theories of defeasible reasoning and argumentation. In particular, Wigmore's method for charting evidence and its use by modern legal evidence scholars is studied in order to give a formal underpinning in terms of logics for defeasible argumentation. Two notions turn out to be crucial, viz. argumentation schemes and empirical generalisations.

This book provides a systematic analysis of many common argumentation schemes and a compendium of 96 schemes. The study of these schemes, or forms of argument that capture stereotypical patterns of human reasoning, is at the core of argumentation research. Surveying all aspects of argumentation schemes from the ground up, the book takes the reader from the elementary exposition in the first chapter to the latest state of the art in the research efforts to formalize and classify the schemes, outlined (...) in the last chapter. It provides a systematic and comprehensive account, with notation suitable for computational applications that increasingly make use of argumentation schemes. (shrink)

Rule-applying legal arguments are traditionally treated as a kind of syllogism. Such a treatment overlooks the fact that legal principles and rules are not statements which describe the world, but rather means by which humans impose structure on the world. Legal rules create legal consequences, they do not describe them. This has consequences for the logic of rule- and principle-applying arguments, the most important of which may be that such arguments are defeasible. This book offers an extensive analysis of the (...) role of rules and principles in legal reasoning, which focuses on the close relationship between rules, principles, and reasons. Moreover, it describes a logical theory which assigns a central place to the notion of reasons for and against a conclusion, and which is especially suited to deal with rules and principles. (shrink)

In this book a theory of reasoning with evidence in the context of criminal cases is developed. The main subject of this study is not the law of evidence but rather the rational process of proof, which involves constructing, testing and justifying scenarios about what happened using evidence and commonsense knowledge. A central theme in the book is the analysis of ones reasoning, so that complex patterns are made more explicit and clear. This analysis uses stories about what happened and (...) arguments to anchor these stories in evidence. Thus the argumentative and the narrative approaches from the research in legal philosophy and legal psychology are combined. Because the book describes its subjects in both an informal and a formal style, it is relevant for scholars in legal philosophy, AI, logic and argumentation theory. The book can also appeal to practitioners in the investigative and legal professions, who are interested in the ways in which they can and should reason with evidence. (shrink)

"A sequel to Pollock's How to Build a Person, this volume builds upon that theoretical groundwork for the implementation of rationality through artificial ...

This book provides a systematic analysis of many common argumentation schemes and a compendium of 96 schemes. The study of these schemes, or forms of argument that capture stereotypical patterns of human reasoning, is at the core of argumentation research. Surveying all aspects of argumentation schemes from the ground up, the book takes the reader from the elementary exposition in the first chapter to the latest state of the art in the research efforts to formalize and classify the schemes, outlined (...) in the last chapter. It provides a systematic and comprehensive account, with notation suitable for computational applications that increasingly make use of argumentation schemes. (shrink)

Written in an outstandingly clear and lively style, this 1969 book provokes its readers to rethink issues they may have regarded as long since settled.

International Commentary on Evidence, 2006 Vol. 4, Issue 2, 1-47 . [link to online version posted].