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)

Precedent is a central feature of legal practice, requiring courts to follow decisions reached in earlier cases, thereby transforming the decisions in individual cases into a source of law. This article examines two major questions associated with precedent: (a) how to characterise the way that precedent operates as a source of law; and (b) how to justify the requirement that courts follow earlier decisions regardless of the merits of those decisions. Precedents are often thought to create general legal rules, but (...) it is controversial whether this is the best way to understand their role in legal reasoning. Equally, it is unclear that the most common justifications for precedent unequivocally vindicate the practice. (shrink)

Research using current literature on legal reasoning was conducted with the goals of (a) determining what skills are most important in good legal reasoning according to such literature, (b) determining the extent to which existing Law School Admission Test item types and subtypes are designed to assess those skills, and (c) suggesting test specifications or new or refined item types and formats that could be developed in the future to assess any important skills that appear [by (a) and (b)] to (...) be measured in a limited or minimal way by the current LSAT. So far as can be determined, such systematic research using legal reasoning literature has never been previously conducted. This report presents the findings of this research. (shrink)

Addressing the slippery slope argument (SSA) in legal contexts from the perspective of pragma-dialectics, this paper elaborates the conditions under which an SSA-scheme instance is used reasonably (rather than fallaciously). We review SSA-instances in past legal decisions and analyze the basic legal SSA-scheme. By illustrating the institutional preconditions influencing the reasoning by which an SSA moves forward, we identify three sub-schemes (causal SSA, analogical SSA, and Sorites SSA). For each sub-scheme we propose critical questions, as well as four rules that (...) clarify when the SSA scheme is used reasonably. The institutional preconditions make the analogical SSA expectable in common law contexts; the Sorites SSA is expectable in civil law contexts; whereas the causal SSA is common to both contexts. This result should inform future work on the identification of typical argumentative patterns for the SSA in legal contexts. (shrink)

In attempting to build intelligent litigation support tools, we have moved beyond first generation, production rule legal expert systems. Our work integrates rule based and case based reasoning with intelligent information retrieval.When using the case based reasoning methodology, or in our case the specialisation of case based retrieval, we need to be aware of how to retrieve relevant experience. Our research, in the legal domain, specifies an approach to the retrieval problem which relies heavily on an extended object oriented/rule based (...) system architecture that is supplemented with causal background information. We use a distributed agent architecture to help support the reasoning process of lawyers. (shrink)

Reasoners compare problems to prior cases to draw conclusions about a problem and guide decision making. All Case-Based Reasoning (CBR) employs some methods for generalizing from cases to support indexing and relevance assessment and evidences two basic inference methods: constraining search by tracing a solution from a past case or evaluating a case by comparing it to past cases. Across domains and tasks, however, humans reason with cases in subtly different ways evidencing different mixes of and mechanisms for these components.In (...) recent CBR research in Artificial Intelligence (AI), five paradigmatic approaches have emerged: statistically-oriented, model-based, planning/design-oriented, exemplar-based, and adversarial or precedent-based. The paradigms differ in the assumptions they make about domain models, the extent to which they support symbolic case comparison, and the kinds of inferences for which they employ cases. (shrink)

This article describes recent jurisprudential accountsof analogical legal reasoning andcompares them in detail to the computational modelof case-based legal argument inCATO. The jurisprudential models provide a theoryof relevance based on low-levellegal principles generated in a process ofcase-comparing reflective adjustment. Thejurisprudential critique focuses on the problemsof assigning weights to competingprinciples and dealing with erroneously decidedprecedents. CATO, a computerizedinstructional environment, employs ArtificialIntelligence techniques to teach lawstudents how to make basic legal argumentswith cases. The computational modelhelps students test legal hypotheses againsta database of (...) legal cases, draws analogiesto problem scenarios from the database, andcomposes arguments by analogy with a setof argument moves. The CATO model accountsfor a number of the important featuresof the jurisprudential accounts, includingimplementing a kind of reflective adjustment.It also avoids some of the problems identifiedin the critique; for instance, it deals withweights in a non-numeric, context-sensitivemanner. The article concludes by describingthe contributions AI research can make tojurisprudential investigations of complexcognitive phenomena of legal reasoning. Forinstance, unlike the jurisprudential models,CATO provides a detailed account of how togenerate multiple interpretations of a citedcase, downplaying or emphasizing the legalsignificance of distinctions in terms of thepurposes of the law as the argument contextdemands. (shrink)

Legislatures enact laws and the courts interpret them. Under the doctrine of legislative supremacy, a judge is not free to ignore or modify a statutory provision in order to substitute a rule that seems to him to be better reasoned; thus where the language of a statute is clear and unambiguous, interpretation is unnecessary and it must be enforced according to its terms. Nevertheless, gaps and ambiguities can arise and, in such cases, courts apply interpretive rules, or ‘canons of construction’, (...) to resolve these ambiguities. One frequently invoked rule requires that words that are not defined by a statute be given their ordinary meaning by the interpreting court. In recent years, the United States Supreme Court has increasingly relied upon dictionary definitions in applying this rule. The Court’s use of dictionaries as authority for its interpretations incorporates the assumption that the dictionary is the best source for ascertaining the meaning of statutory texts. This article challenges that assumption on linguistic grounds. I argue that the focus on definitions skews the interpretation of statutory language by isolating words from their semantic context. By comparing two cases in which the Court used dictionary definitions to a third case in which the definition used by the Court was contained in the statute itself, I demonstrate that the ordinary meaning of legal terms cannot be determined by dictionary definitions. (shrink)