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.

Review of Susan Haack Defending Science -- Within Reason: Between Scientism and Cynicism.

Sweeping in scope, penetrating in analysis, and generously illustrated with examples from the history of science, this new and original approach to familiar questions about scientific evidence and method tackles vital questions about science and its place in society. Avoiding the twin pitfalls of scientism and cynicism, noted philosopher Susan Haack argues that, fallible and flawed as they are, the natural sciences have been among the most successful of human enterprises-valuable not only for the vast, interlocking body of knowledge they (...) have discovered, and not only for the technological advances that have improved our lives, but as a manifestation of the human talent for inquiry at its imperfect but sometimes remarkable best. This wide-ranging, trenchant, and illuminating book explores the complexities of scientific evidence, and the multifarious ways in which the sciences have refined and amplified the methods of everyday empirical inquiry; articulates the ways in which the social sciences are like the natural sciences, and the ways in which they are different; disentangles the confusions of radical rhetoricians and cynical sociologists of science; exposes the evasions of apologists for religious resistance to scientific advances; weighs the benefits and the dangers of technology; tracks the efforts of the legal system to make the best use of scientific testimony; and tackles predictions of the eventual culmination, or annihilation, of the scientific enterprise. Writing with verve and wry humor, in a witty, direct, and accessible style, Haack takes readers beyond the "Science Wars" to a balanced understanding of the value, and the limitations, of the scientific enterprise. (shrink)

Aulis Aarnio addresses the question of how legal interpretations should be justified. Aarnio considers a justification to be rational only if the justification process has been conducted in a rational way, and if the final result of this process is acceptable to the legal community. According to Aarnio, a theory concerning the justification of legal interpretations should contain a procedural component specifying the conditions of rationality for legal discussions, and a substantial component specifying the material conditions of acceptability for the (...) final result. The procedural component of Aarnio’s theory formulates rules for the rationality of legal discussions. The substantial component specifies when the result of a legal interpretation can be called acceptable. Aarnio considers such a result acceptable if it is acceptable to a particular legal community in which there is consensus with respect to certain norms and values. (shrink)

. A heuristic search procedure for inventing legal arguments is built on two tools already widely in use in argumentation. Argumentation schemes are forms of argument representing premise‐conclusion and inference structures of common types of arguments. Schemes especially useful in law represent defeasible arguments, like argument from expert opinion. Argument diagramming is a visualization tool used to display a chain of connected arguments linked together. One such tool, Araucaria, available free at , helps a user display an argument on the (...) computer screen as an inverted tree structure with an ultimate conclusion as the root of the tree. These argumentation tools are applicable to analyzing a mass of evidence in a case at trial, in a manner already known in law using heuristic methods and Wigmore diagrams . In this paper it is shown how they can be automated and applied to the task of inventing legal arguments. One important application is to proof construction in trial preparation. (shrink)

In this paper we will analyse the issue of defeasibility in the law, taking into account research carried out in philosophy, artificial intelligence and legal theory. We will adopt a very general idea of legal defeasibility, in which we will include all different ways in which certain legal conclusions may need to be abandoned, though no mistake was made in deriving them. We will argue that defeasibility in the law involves three different aspects, which we will call inference‐based defeasibility, process‐based (...) defeasibility, and theory‐based defeasibility. Only the integration of these three perspectives allows us to provide a satisfactory account of the role of defeasibility in legal reasoning. (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)

There is tension between the adversarialism of the U.S. legal culture and the investigative procedures of the sciences, and between the law's concern for finality and the open‐ended fallibilism of science. A long history of attempts to domesticate scientific testimony by legal rules of admissibility has left federal judges with broad screening responsibilities; recent adaptations of adversarialism in the form of court‐appointed experts have been criticized as “inquisitorial,” even “undemocratic.” In exploring their benefits and disadvantages, it would make sense to (...) look to the experience of other legal systems. (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.

A detailed treatment regarding the diverse properties and uses of evidence and the judgmental tasks they entail. Examines various processes by which evidence may be developed or discovered. Considers the construction of arguments made in defense of the relevance and credibility of individual items and masses of evidence as well as the task of assessing the inferential force of evidence. Includes over 100 numerical examples to illustrate the workings of diverse probabilistic expressions for the inferential force of evidence and the (...) subtleties they reveal. (shrink)

A leading expert in informal logic, Douglas Walton turns his attention in this new book to how reasoning operates in trials and other legal contexts, with special emphasis on the law of evidence. The new model he develops, drawing on methods of argumentation theory that are gaining wide acceptance in computing fields like artificial intelligence, can be used to identify, analyze, and evaluate specific types of legal argument. In contrast with approaches that rely on deductive and inductive logic and rule (...) out many common types of argument as fallacious, Walton’s aim is to provide a more expansive view of what can be considered "reasonable" in legal argument when it is construed as a dynamic, rule-governed, and goal-directed conversation. This dialogical model gives new meaning to the key notions of relevance and probative weight, with the latter analyzed in terms of pragmatic criteria for what constitutes plausible evidence rather than truth. (shrink)

A new pragmatic approach, based on the latest developments in argumentation theory, analyzing appeal to expert opinion as a form of argument. Reliance on authority has always been a common recourse in argumentation, perhaps never more so than today in our highly technological society when knowledge has become so specialized—as manifested, for instance, in the frequent appearance of "expert witnesses" in courtrooms. When is an appeal to the opinion of an expert a reasonable type of argument to make, and when (...) does it become a fallacy? This book provides a method for the evaluation of these appeals in everyday argumentation. Specialized domains of knowledge such as science, medicine, law, and government policy have gradually taken over as the basis on which many of our rational decisions are made daily. Consequently, appeal to expert opinion in these areas has become a powerful type of argument. Challenging an argument based on expert scientific opinion, for example, has become as difficult as it once was to question religious authority. Walton stresses that even in cases where expert opinion is divided, the effect of it can still be so powerful that it overwhelms an individual's ability to make a decision based on personal deliberation of what is right or wrong in a given situation. The book identifies the requirements that make an appeal to expert opinion a reasonable or unreasonable argument. Walton's new pragmatic approach analyzes that appeal as a distinctive form of argument, with an accompanying set of appropriate critical questions matching the form. Throughout the book, a historical survey of the key developments in the evolution of the argument from authority, dating from the time of the ancients, is given, and new light is shed on current problems of "junk science" and battles between experts in legal argumentation. (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 is an introductory guide to the basic principles of constructing good arguments and criticizing bad ones. It is nontechnical in its approach, and is based on 150 key examples, each discussed and evaluated in clear, illustrative detail. The author explains how errors, fallacies, and other key failures of argument occur. He shows how correct uses of argument are based on sound argument strategies for reasoned persuasion and critical questions for responding. Among the many subjects covered are: techniques of posing, (...) replying to, and criticizing questions, forms of valid argument, relevance, appeals to emotion, personal attack, uses and abuses of expert opinion, problems in deploying statistics, loaded terms, equivocation, and arguments from analogy. (shrink)

In this important book, a distinguished legal scholar examines how the legal culture and institutions in Anglo-American countries affect the way in which evidence is gathered, sifted, and presented to the courts.

In response to the claim that many judges are deficient in their understanding of scientific methodology, we identify in recent cases (i) a pragmatic perspective on the part of federal appellate judges when they reverse trial judges who tend to idealize science (i.e., who do not appreciate the local and practical goals and limitations of science), and (ii) an educational model of judicial gatekeeping that results in reversal of trial judges who defer to the social authority of science (i.e., who (...) mistake authority for reliability). Next, we observe that courts (in the cases we analyze) are not interested in pragmatically constructing legal science, but rather attempt to ensure that science itself, conceived pragmatically (i.e., without idealizing science), is appropriated in law. We conclude that trial judges who fail to appreciate the social, institutional, and rhetorical aspects of science tend to reject reliable - albeit pragmatic - science, to welcome unreliable - albeit authoritative - science, and thereby to create a body of legal science that is out of sync with mainstream science. (shrink)