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)

Identifying, classifying, and analyzing arguments in legal discourse has been a prominent area of research since the inception of the argument mining field. However, there has been a major discrepancy between the way natural language processing (NLP) researchers model and annotate arguments in court decisions and the way legal experts understand and analyze legal argumentation. While computational approaches typically simplify arguments into generic premises and claims, arguments in legal research usually exhibit a rich typology that (...) is important for gaining insights into the particular case and applications of law in general. We address this problem and make several substantial contributions to move the field forward. First, we design a new annotation scheme for legal arguments in proceedings of the European Court of Human Rights (ECHR) that is deeply rooted in the theory and practice of legal argumentation research. Second, we compile and annotate a large corpus of 373 court decisions (2.3M tokens and 15k annotated argument spans). Finally, we train an argument mining model that outperforms state-of-the-art models in the legal NLP domain and provide a thorough expert-based evaluation. All datasets and source codes are available under open lincenses at https://github.com/trusthlt/mining-legal-arguments. (shrink)

Robert Alexy develops his influential theory of legal reasoning exploring the nature of legal argumentation and its relation to practical reasoning. In doing so he sheds light on fundamental questions of law and rationality, which are as crucial to practising lawyers and law students as they are to scholars of legal theory.

The paper reconstructs Luhmann’s conception of legal argumentation and justice especially focussing on the aspects of contingency and self-referring operative closure. The aim of his conception is to describe/explain in a disenchanted way—from an external, of “second order” point of view—the work on adjudication, which, rather idealistically, lawyers and judges present as being a matter of reason. As a consequence of some surface similarities with Derrida’s deconstructive philosophy of justice, Teubner proposes integrating the supposed reductive image of formal (...) justice described by Luhmann with the ideal conception of justice presented by Derrida. Here this kind of attempt is rejected as epistemologically wrong. In addition, Luhmann’s theory is argued to have other shortcomings, namely: the failure to understand the pragmatic function of principles, and the incapacity to describe the current legal questions linked with cultures and legal pluralism, which characterise our society. (shrink)

A Bayesian network (BN) is a graphical model of uncertainty that is especially well suited to legal arguments. It enables us to visualize and model dependencies between different hypotheses and pieces of evidence and to calculate the revised probability beliefs about all uncertain factors when any piece of new evidence is presented. Although BNs have been widely discussed and recently used in the context of legal arguments, there is no systematic, repeatable method for modeling legal arguments as (...) BNs. Hence, where BNs have been used in the legal context, they are presented as completed pieces of work, with no insights into the reasoning and working that must have gone into their construction. This means the process of building BNs for legal arguments is ad hoc, with little possibility for learning and process improvement. This article directly addresses this problem by describing a method for building useful legal arguments in a consistent and repeatable way. The method complements and extends recent work by Hepler, Dawid, and Leucari (2007) on object-oriented BNs for complex legal arguments and is based on the recognition that such arguments can be built up from a small number of basic causal structures (referred to as idioms). We present a number of examples that demonstrate the practicality and usefulness of the method. (shrink)

Ordinary arguments from authority have the following structure: A says p; A is authoritative on such things; so p. Legal actors use such arguments whenever they ground their decisions on the sheer “say-so” of legislators, judges, scholars, expert witnesses, and so on. This paper focuses on arguments appealing to the authority of scholars, “doctrinal” or “dogmatic” legal scholars in particular. Appeal to doctrinal authority is a puzzling feature of legal argumentation. In what sense are doctrinal scholars (...) “authorities”? Is p, as advanced by a scholar, descriptive or prescriptive? Is scholarly authority grounded on expertise or something different? The paper addresses these questions. (shrink)

This article utilises Luhmann's functional analysis to investigate the role played by legal argumentation within the legal system. Luhmann's sociological observations on this subject suggest an alternative to jurisprudential approaches that understand legal arguments and consequent decisions in terms of the relative strengths of the justifications offered in their support. His account examines the role played by legal argumentation in allowing the legal system to evolve in response to society's increasing complexity. The concepts (...) he employs to analyse this evolutionary capacity of law, developed from their origins in information theory, are redundancy and variety. Beginning with the work of Dworkin the article opens up Luhmann's analysis to consider how legal argumentation operates both as a grounded form of communication, capable of identifying weak or unsustainable interpretations of legal texts, and a mechanism for evolving law in the direction of increasing complexity. (shrink)

Robert Alexy develops his influential theory of legal reasoning exploring the nature of legal argumentation and its relation to practical reasoning. In doing so he sheds light on fundamental questions of law and rationality, which are as crucial to practising lawyers and law students as they are to scholars of legal theory.

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)

Bayesian models of legal arguments generally aim to produce a single integrated model, combining each of the legal arguments under consideration. This combined approach implicitly assumes that variables and their relationships can be represented without any contradiction or misalignment, and in a way that makes sense with respect to the competing argument narratives. This paper describes a novel approach to compare and ‘average’ Bayesian models of legal arguments that have been built independently and with no attempt to (...) make them consistent in terms of variables, causal assumptions or parameterization. The approach involves assessing whether competing models of legal arguments are explained or predict facts uncovered before or during the trial process. Those models that are more heavily disconfirmed by the facts are given lower weight, as model plausibility measures, in the Bayesian model comparison and averaging framework adopted. In this way a plurality of arguments is allowed yet a single judgement based on all arguments is possible and rational. (shrink)

We present an annotation scheme describing the argument structure of judgement documents, a central construct in Japanese law. To support the final goal of this work, namely summarisation aimed at the legal professions, we have designed blueprint models of summaries of various granularities, and our annotation model in turn is fitted around the information needed for the summaries. In this paper we report results of a manual annotation study, showing that the annotation is stable. The annotated corpus we created (...) contains 89 documents. We also designed and implemented the first two stages of an algorithm for the automatic extraction of argument structure, and present evaluation results. (shrink)

Ethical, Religious and Legal Arguments in the Current Debate over Euthanasia in Spain In the last ten years, there have been several cases in Spain (Ramón Sampedro, Leganés, Jorge León that have led to an intense social debate on euthanasia. The recent case of Inmaculada Echevarría, a woman suffering from a serious disease that kept her immobilized in bed, has revived the debate on euthanasia in Spain. On 18 October 2006 she held a press conference and publicly asked to (...) be disconnected from the ventilator that kept her alive. After a long ethical, religious, legal, and social debate, the patient was disconnected on 14 March 2007 after being adequately sedated. As a consequence, the patient died. In our paper we defend the need for a radical and intercultural democracy and present the main ethical, religious and legal arguments on euthanasia that are being posed in Spain and in Europe as a debate that should help to build a radical and intercultural democracy at a European level. (shrink)

The BankXX system models the process of perusing and gathering information for argument as a heuristic best-first search for relevant cases, theories, and other domain-specific information. As BankXX searches its heterogeneous and highly interconnected network of domain knowledge, information is incrementally analyzed and amalgamated into a dozen desirable ingredients for argument (called argument pieces), such as citations to cases, applications of legal theories, and references to prototypical factual scenarios. At the conclusion of the search, BankXX outputs the set of (...) argument pieces filled with harvested material relevant to the input problem situation.This research explores the appropriateness of the search paradigm as a framework for harvesting and mining information needed to make legal arguments. In this article, we describe how legal research fits the heuristic search framework and detail how this model is used in BankXX. We describe the BankXX program with emphasis on its representation of legal knowledge and legal argument. We describe the heuristic search mechanism and evaluation functions that drive the program. We give an extended example of the processing of BankXX on the facts of an actual legal case in BankXX's application domain — the good faith question of Chapter 13 personal bankruptcy law. We discuss closely related research on legal knowledge representation and retrieval and the use of search for case retrieval or tasks related to argument creation. Finally we review what we believe are the contributions of this research to the understanding of the diverse disciplines it addresses. (shrink)

This essay discusses the most recent manifestations of the debate of the law and literature movement. The essay traces the evolution of the Law and Literature schools and identifies some of their adherents and conclusions, shows how these schools have influenced the conceptual development and teaching of American law, presents connections between the Critical Legal Studies and Law and Economics movements in the U.S., and raises questions about the Law and Literature movement.

In this paper a theoretical definition that helps to explain how the logical structure of legal presumptions is constructed by applying the Carneades model of argumentation developed in artificial intelligence. Using this model, it is shown how presumptions work as devices used in evidentiary reasoning in law in the event of a lack of evidence to assist a chain of reasoning to move forward to prove or disprove a claim. It is shown how presumptions work as practical devices (...) that may be useful in cases in which there is insufficient evidence to prove the claim to an appropriate standard of proof. (shrink)

The article discusses topics in the context of contemporary legal argumentation. It starts with a sketch of the development of topics from ancient times until the present day. Here the author focuses on the theory of the German legal philosopher Theodor Viehweg, which was most influential to legal argumentation in the 20th century. Then a modern concept of topics is introduced and finally the author discusses the role of topics in contemporary legal argumentation. (...) In this part the distinction between topoi in the weak sense (practically all argumentation schemes) and in the strong sense (specific legal topoi as listed by Gerhard Struck in 1971 is introduced. The author argues that Viehweg’s claim that topics plays an important role in legal argumentation is problematic, because topoi in the weak sense are certainly of high importance, but this is almost trivial. Topoi in the strong sense on the other hand are only of minor importance for legal practice. What characterises legal discourse much more is a set specific pragmatic discourse rules, discussed at the end of the paper. (shrink)

In this paper we use a series of examples to show how oppositions and dichotomies are fundamental in legal argumentation, and vitally important to be aware of, because of their twofold nature. On the one hand, they are argument structures underlying various kinds of rational argumentation commonly used in law as a means of getting to the truth in a conflict of opinion under critical discussion by two opposing sides before a tryer of fact. On the other (...) hand, they are argument structures underling moves made in strategic advocacy by both sides that function as platforms for different kinds of questionable argumentation tactics and moves that are in some instances tricky and deceptive. (shrink)

This study examines the concept of argumentation empirically, to correct the normative conception of argumentation adopted by most scholars since Aristotle. They are not interested in what argumentation is, but in what it ought to be. The pre-Aristotelian approach is preferable, because it recognizes that argumentation, although it includes persuasion, also embraces other eristic techniques in which the speaker does not necessarily seek to persuade, but simply to prevail. This broader descriptive and pragmatic analysis explains the (...) different ways in which discourse actually occurs and particular arguments succeed, leaving in a secondary place the opinion of each author on how they should be. (shrink)

Wigmore thought that there was a science of proof underlying legal reasoning that could be displayed in any given case as a graphic sequence of argumentation from the evidence in the case leading to the ultimate probandum. Argumentation technology has now vindicated this approach by providing useful qualitative methods that can be applied to identifying, analyzing, and evaluating the pro and con arguments put forward by both sides in a trial. In this chapter, it is shown how (...) to apply argumentation schemes, such as argument from witness testimony, using argument diagrams applied to typical sequences of evidence-based legal reasoning in which there is a successive refinement of arguments displayed as the evidence comes into a case. It is shown how argument from applying rules to cases, teleological, argument from expert witness testimony, and abductive reasoning are centrally important for this purpose. (shrink)

This article provides an assessment of the merits of recent theories of legal reasoning. After a quick historical aperçu a number of models of legal argumentation are presented and discussed, with an eye to their mutual connection. An initial conclusion is that universalizability and discursivity are the common features of those models. The focal question dealt with, however, is that of the impact of the argumentative paradigms of adjudication on the very concept of law. Here the contention (...) is that an argumentative style of reasoning contributes to rendering the structure of the law itself and its operations argumentative as well. By so doing the latter are—so to say—civilized and made less truculent. They will thus be able to develop more in conformity with a democratic form of life. (shrink)

Walton’s book aims to supply a fresh method for evaluating logical reasoning and legal argumentation. Drawn from philosophy, law and science, Walton’s method rests on a theory of “plausibilistic” reasoning or “probabilism”. According to plausibilistic reasoning, we can logically infer conclusions from a set of premises even though the premises are neither definite nor of a measurable probability. We may tentatively draw such inferences so long as they rest on generally valid premises. To illustrate this method, Walton cites (...) a famous example from Wigmore: A man had no money before a robbery, but suddenly came into a great deal of money following the robbery. It is therefore plausible to infer that the man committed the robbery. (shrink)

While the formal treatment of arguments in the late medieval modi arguendi owes much to dialectic, this does not remove the substance and function of the argumentative modes discussed from the realm of rhetoric. These works, designed to teach law students skills in legal argumentation, remain importantly focused on persuasive features of argumentation which have traditionally been strongly associated with a rhetorical approach, particularly in efforts to differentiate from it dialectic as a more strictly scientific and logical (...) form of reasoning. This also sheds some light on the relative roles logic and rhetoric play in the legal discourse of our own time. In their approach to persuasive legal discourse, the modi arguendi stand between the argumentative rhetorics of Antiquity and the rhetoricized dialectics of the Renaissance, and by linking the minute technicalities of professionalized law with broad general considerations of justice, utility, nature, and emotion, they mediate between the modem trend towards atomized field-specific rhetorics and the classical idea of a unified civic rhetoric. (shrink)

This chapter contains sections titled: The Moral Duty to Assist Others in Their Health Care Health Care Should Be Provided by the Government The Duty to Provide Truly Universal Health Care Rejecting the Liberal Model.

In this article we evaluate the BankXX program from several perspectives. BankXX is a case-based legal argument program that retrieves cases and other legal knowledge pertinent to a legal argument through a combination of heuristic search and knowledge-based indexing. The program is described in detail in a companion article in Artificial Intelligence and Law 4: 1--71, 1996. Three perspectives are used to evaluate BankXX:(1) classical information retrieval measures of precision and recall applied against a hand-coded baseline; (2) (...) knowledge-representation and case-based reasoning, where the baseline is provided by the functionality of a well-known case-based argument program, HYPO (Ashley, 1990); and (3) search, in which the performance of BankXX run with various parameter settings, for instance, resource limits, is compared. In this article we report on an extensive series of experiments performed to evaluate the program. We also describe two additional experiments concerning(1) the program's search behavior; and (2) the use of a modified form of precision and recall based on case similarity. Finally we offer some general conclusions that might be drawn from these particular experiments. (shrink)

This paper develops a virtue-account of legal reasoning which significantly differs from standard, principle-based, theories. A virtue approach to legal reasoning highlights the relevance of the particulars to sound legal decision-making, brings to light the perceptual and affective dimensions of legal judgment, and vindicates the relevance of description and specification to good legal reasoning. After examining the central features of the theory, the paper proposes a taxonomy of the main character traits that legal decision-makers (...) need to possess to successfully engage in legal reasoning. The paper concludes by discussing an array of strategies in legal education, institutional design, and legal culture that can be put in place to work virtue in legal decision-making. (shrink)

This essay discusses the developments and trends of research in legalargumentation of the last 25 years. The essay starts with a survey of thevarious approaches which can be distinguished: the logical approach, therhetorical approach, and the dialogical approach. Then it identifies varioustopics in the research, which constitute the various components of aresearch programme of legal argumentation: the philosophical component, thetheoretical component, the reconstruction component, the empiricalcomponent, and the practical component. It concludes with a discussion ofthe main trends in (...) the research of the last 25 years. (shrink)

According to Dascal, controversy is characterised by a special kind of rationality, one result thereof being the unique contribution of this kind of polemics to the growth of knowledge. This, in turn, implies that complete cooperation may be detrimental for the efficiency of communication. In this article I discuss the kind of rationality that characterises controversy in legal discourse, in order to provide additional support to Dascal’s thesis about the uniqueness of the rationality of this kind of polemic exchange. (...) I present empirical evidence supporting the conclusion that we may characterise the rationality inherent in controversy by its tolerance to inconsistency; I elucidate the tolerance to inconsistency of the rationality of legal polemic by showing that the norms recommended by the Israeli Supreme Court in the domain of conjugal relationships between men and women verge on inconsistency: On the one hand, the legal system defends the right of women over their bodies, including a woman’s right to establish a romantic relationship, regardless of the nature of the relationship she has with other men; on the other hand, the court acknowledges a man’s uncontrolled tendency to impose monogamous behaviour on his female partner. (shrink)

The research described here explores the idea of using Supreme Court oral arguments as pedagogical examples in first year classes to help students learn the role of hypothetical reasoning in law. The article presents examples of patterns of reasoning with hypotheticals in appellate legal argument and in the legal classroom and a process model of hypothetical reasoning that relates them to work in cognitive science and Artificial Intelligence. The process model describes the relationships between an advocate’s proposed test (...) for deciding a case or issue, the facts of the hypothetical and of the case to be decided, and the often conflicting legal principles and policies underlying the issue. The process model of hypothetical reasoning has been partially implemented in a computerized teaching environment, LARGO (“Legal ARgument Graph Observer”) that helps students identify, analyze, and reflect on episodes of hypothetical reasoning in oral argument transcripts. Using LARGO, students reconstruct examples of hypothetical reasoning in the oral arguments by representing them in simple diagrams that focus students on the proposed test, the hypothetical challenge to the test, and the responses to the challenge. The program analyzes the diagrams and provides feedback to help students complete the diagrams and reflect on the significance of the hypothetical reasoning in the argument. The article reports the results of experiments evaluating instruction of first year law students at the University of Pittsburgh using the LARGO program as applied to Supreme Court personal jurisdiction cases. The learning results so far have been mixed. Instruction with LARGO has been shown to help law student volunteers with lower LSAT scores learn skills and knowledge regarding hypothetical reasoning better than a text-based approach, but not when the students were required to participate. On the other hand, the diagrams students produce with LARGO have been shown to have some diagnostic value, distinguishing among law students on the basis of LSAT scores, posttest performance, and years in law school. This lends support to the underlying model of hypothetical argument and suggests using LARGO as a pedagogically diagnostic tool. (shrink)

While courts depend on expert opinions in reaching sound judgments, the role of the expert witness in legal proceedings is associated with a litany of problems. Perhaps most prevalent is the question of under what circumstances should testimony be admitted as expert opinion. We review the changing policies adopted by American courts in an attempt to ensure the reliability and usefulness of the scientific and technical information admitted as evidence. We argue that these admissibility criteria are best seen in (...) a dialectical context as a set of critical questions of the kind commonly used in models of argumentation. (shrink)

Legal Reason describes and explains the process of analogical reasoning, which is the distinctive feature of legal argument. It challenges the prevailing view, urged by Edward Levi, Cass Sunstein, Richard Posner and others, which regards analogical reasoning as logically flawed or as a defective form of deductive reasoning. It shows that analogical reasoning in the law is the same as the reasoning used by all of us routinely in everyday life and that it is a valid form of (...) reasoning derived from the innate human capacity to recognize the general in the particular, on which thought itself depends. The use of analogical reasoning is dictated by the nature of law, which requires the application of rules to particular facts. Written for scholars as well as students and persons generally who are interested in law, Legal Reason is written in clear, accessible prose, with many examples drawn from the law and from everyday experience. (shrink)

This paper explores two persistent questions in the literature on presumptions: the place and the nature of presumptions in law and legal argumentation. These questions were originally raised by James Bradley Thayer, one of the masters of the Law of Evidence and the author of the classic chapter devoted this subject in A preliminary treatise on Evidence. Like Thayer, I believe that these questions deserve attention. First the paper shows that the connection between presumptions and argumentation is (...) a constant feature in the literature on presumptions, since its foundation in the Middle Ages to modern times. James Bradley Thayer was probably the last jurist who clearly saw that presumptions belong to argumentation. Second, the paper examines two sources of controversy in the language of presumptions. First, “presumption” is an ambiguous word in the legal discourse. As a result, it is almost impossible to provide a clear and succinct answer to the question “What is a presumption?”. Second, there are at least four reconstructions of the concept of presumption whose merits and shortcomings are relevant to explore. The analysis presented here may be of interest for legal and non-legal scholars and, hopefully, it may help to shed light on the possibilities and limits of an interdisciplinary dialogue about presumptions. (shrink)

The author argues that simple constructive dilemma is a valuable argument form for reasoning under relative conditions of uncertainty. When applied to legal argument this value of simple constructive dilemma is shown in its political, strategic, rhetorical, and especially economic, uses by lawyers and judges. After considering some examples of the use of the form by trial lawyers, the author gives examples of the more interesting use of the form by appellate courts. Research into the use of simple constructive (...) dilemma by appellate courts helps us to understand how those courts distribute judicial resources. It also helps us to understand the political role of the appellate courts with respect to the doctrine of the separation of powers. Given some of the specific examples of legal reasoning used by the appellate courts presented in this article, and given the discussion of the doctrine of precedent, the article’s focus is on common law legal systems of the Anglo-American-type. (shrink)