Formal Models of Legal Reasoning

This chapter briefly reviews the present state of judgment aggregation theory and tentatively suggests a future direction for that theory. In the review, we start by emphasizing the difference between the doctrinal paradox and the discursive dilemma, two idealized examples which classically serve to motivate the theory, and then proceed to reconstruct it as a brand of logical theory, unlike in some other interpretations, using a single impossibility theorem as a key to its technical development. In the prospective part, having (...) mentioned existing applications to social choice theory and computer science, which we do not discuss here, we consider a potential application to law and economics. This would be based on a deeper exploration of the doctrinal paradox and its relevance to the functioning of collegiate courts. On this topic, legal theorists have provided empirical observations and theoretical hints that judgment aggregation theorists would be in a position to clarify and further elaborate. As a general message, the chapter means to suggest that the future of judgment aggregation theory lies with its applications rather than its internal theoretical development. (shrink)

We argue that legal argumentation, as the subject matter as well as a special subfield of Argumentation Studies (AS), has to be examined by making skilled use of the full panoply of tools such as argumentation and story schemes which are at the forefront of current work in AS. In reviewing the literature, we make explicit our own methodological choices (particularly regarding the place of normative deliberation in practical reasoning) and then illustrate the implications of such an approach through the (...) analysis of a case study in the English law of evidence. We argue that a clear distinction must be drawn between practical argumentation and stories. Because of the institutional separation between legal judgment and fact-finding in common-law jury trials, we argue for the combination of argument and story-based analysis. (shrink)

It’s widely accepted that normativity is not subject to truth values. The underlying reasoning is that truth values can only be predicated of descriptive statements; normative statements are prescriptive, not descriptive; thus truth value predicates cannot be assigned to normative statements. Hence, deonticity lacks logical semantics. This semantic monism has been challenged over the last decades from a series of perspectives that open the way for legal logics with imperative semantics. In the present paper I will go back to Kant (...) and review his understanding of practical judgments, presenting it as supported by a pluralistic semantics. From this perspective a norm of Law is a logical expression that includes as content a generic description of a possible behavior by a generality of juridical agents, and assigns to that content the assertion of its obligatory character, accompanied by a disincentive for non-compliance. From this perspective legal norms can be syntactically formalized and assigned appropriate semantic values in such terms that they can be incorporated into valid inferential schemes. The consequence is that we can put together legal logics that handle both the phenomenal and the deontic dimensions of legality. (shrink)

Fallgeschichten werden seit dem 18. Jahrhundert zunehmend genutzt, um juristisches, psychologisches und medizinisches Wissen einer grösseren Öffentlichkeit zu vermitteln. In den letzten zehn Jahren haben sie auch in den Geistes- und Sozialwissenschaften mehr Aufmerksamkeit erfahren. Die Diskussion über paradigmatische Fälle in diesem Band zielt darauf ab, Fallgeschichten in ihrer Funktion als besonders anschauliche oder lehrreiche Beispiele in verschiedenen historischen Kontexten zu untersuchen und zu vergleichen. Die in diesem Heft versammelten Texte gehen der Frage nach, wie Fälle dazu beitragen, Debatten zu (...) verdichten und Entwicklungen erzählbar zu machen, wie sie über den Einzelfall hinausgehendes Wissen generieren und so paradigmatischen Status erlangen. Neben konzeptuellen Gesichtspunkten widmen sich die Beiträge mehreren Forschungsfeldern, darunter der Rechts- und Medizingeschichte, der Geschichte der Geschichtsschreibung, literarischen Fällen, den Sozialwissenschaften und der Technikgeschichte. (shrink)

Langdellian “science” and its “formalism” ignore ways form permits and even creates freedom of choice. For example, as Wordsworth notes, though the weaver is restricted by what his form of loom can weave, the weaver may nonetheless choose what and how he weaves. Furthermore, the loom creates weaving possibilities that do not exist without it. Such freedom alongside form is often lost on lawyers, judges, and teachers trained primarily in Langdellian redacted appellate cases where “facts” and other framed matters often (...) wrongly appear as simply given. Similarly, in the context of their redacted appellate cases, many current students may only see constraint in IRAC (Issue-Rule-Application-Conclusion) and other thought forms rather than the fastidious freedoms such forms both provide and create. -/- Overlooking such freedoms is not only misleading in itself. It also misses the need to study how such freedoms are and should be exercised. When facts are simply presented as “given” and strategic and other choices go unrecorded and unnoticed in redacted appellate opinions, no thorough analysis of these overlooked subjects can occur. This is extremely troubling since such overlooked subjects are at the very heart of the lawyer’s craft. -/- Attempting to remedy such Langdellian shortcomings, this article explores, among other things, five basic levels of thought and the framing choices in such levels of thought: references, issues, rules, application of rules, and conclusions. Though often merely taken as “given” in redacted appellate opinions, a good grasp of reference assures that parties are in fact talking about the same matter or matters (the “reference”). It also increases the likelihood of ascertaining and properly framing all the relevant “facts” in a manner reasonably and ethically consistent with a client’s real interests. Similarly, focusing on flexibility of issue framing both brings necessary focus on what is important in the reference and, to the extent reasonable and ethical, again increases the likelihood of frames most consistent with a client’s real interests. A good grasp of applicable rules and how to frame and apply them on its face increases the likelihood of representing a client well. A good grasp of conclusions and how to frame and hedge them also does the same. -/- Grasping the multilevel complexities in play at these multiple levels pushes us beyond briefing redacted appellate cases to the much more difficult and stimulating work of exploring and teaching good legal thought at all its levels. Legal writing professors are pioneers in this regard and others in the academy can learn much from them. -/- Keywords: RIRAC, IRAC, CREAC, Reference, Issue, Analysis, Rule, Application, Conclusion, Frame, Framing, Metaphor, Concept, Category, Legal Thought, Legal Analysis, Rhetoric, Langdell, Wordsworth, Form, Formalism, Sonnet, Text. (shrink)

This paper challenges the Critical Legal Studies (CLS) claims of legal indeterminacy. It shall use a legal formalist logic and language as its main assertion, further maintaining that the CLS claims is only grounded in ambiguity and confusion. CLS is a legal theory that challenges and overturns accepted norms and standards in legal theory and practice. They maintained that law in the historical and contemporary society has an alleged impartiality, and it is used as a tool of privilege and power (...) – law is politics. Consequently, CLS maintained that these results to indeterminacy of law. Legal indeterminacy can be summed up as contrary to the common understanding that legal materials, statutes and case law, do not really answer legal disputes. Legal principles and doctrines, as CLS scholars claim, are said to be indeterminate, for it is riddle with gaps, conflicts, and anomalies that are widely present even in simple cases. Legal indeterminacy also rises because of the underlying political power – law is politics – that implicates law as merely a tool for oppression. This thesis shows that CLS assertions with legal indeterminacy is only grounded on ambiguity. On one hand, using the main concept of legal formalist logic and language grounded with sub-arguments: inherent generality of legal language, reasoned elaboration, and neutral principles, it refutes the CLS claims of legal indeterminacy. On the other, the paper maintains that their main reason of legal indeterminacy, ‘law is politics’, is merely a statement of fact that currently happens in society is sentimental and weak through counterexamples. (shrink)

Recent attempts to resolve the Paradox of the Gatecrasher rest on a now familiar distinction between individual and bare statistical evidence. This paper investigates two such approaches, the causal approach to individual evidence and a recently influential (and award-winning) modal account that explicates individual evidence in terms of Nozick's notion of sensitivity. This paper offers counterexamples to both approaches, explicates a problem concerning necessary truths for the sensitivity account, and argues that either view is implausibly committed to the impossibility of (...) no-fault wrongful convictions. The paper finally concludes that the distinction between individual and bare statistical evidence cannot be maintained in terms of causation or sensitivity. We have to look elsewhere for a solution of the Paradox of the Gatecrasher. (shrink)

Aunque el derecho probatorio y el derecho procesal se han dedicado desde siempre al estudio de los problemas relacionados con las pruebas y el establecimiento de los hechos en los procesos judiciales, el énfasis ha estado siempre en el aspecto formal, doctrinal y procedimental en detrimento de los fundamentos filosóficos y teóricos. Durante los últimos años ha habido un intento sostenido de explorar estos fundamentos combinando no sólo las herramientas tradicionales proporcionadas por la lógica, la gramática y la retórica, sino (...) también los avances hechos en ciencias como la estadística y la probabilidad, la medicina y la psicología forenses, la psicología de la percepción, la epistemología y la filosofía de la ciencia. El presente libro reúne las contribuciones de destacados juristas y filósofos latinoamericanos a esta nueva perspectiva interdisciplinaria, conocida como epistemología jurídica. El libro está dividido en tres grandes temas: la primera parte explora los problemas epistemológicos del conocimiento de los hechos en los procesos judiciales; la segunda se enfoca en el problema de los estándares de prueba; y la sección final discute el testimonio de los expertos. En su conjunto el libro ofrece un panorama tanto de los problemas centrales de la epistemología jurídica, como del estado del arte de la disciplina. (shrink)

En el presente artículo se examinan varias propuestas que abordan la argumentación como un ejercicio válido y necesario de control judicial; ello, a través del estudio de diversos elementos doctrinales, como lo son la representación democrática argumentativa, la interpretación previa y la debida justificación de las decisiones, así como la ponderación y la aplicación de los principios, entre otros. Al margen de lo anterior, nuestra intención no es otra sino la de presentar una descripción del estado del arte de dichas (...) cuestiones, el cual es presentado en un repaso detallado en varios planteamientos teóricos que, directa o indirectamente, evalúan el papel de la argumentación como eje del control judicial. (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)

The forensic two-trace problem is a perplexing inference problem introduced by Evett (J Forensic Sci Soc 27:375–381, 1987). Different possible ways of wording the competing pair of propositions (i.e., one proposition advanced by the prosecution and one proposition advanced by the defence) led to different quantifications of the value of the evidence (Meester and Sjerps in Biometrics 59:727–732, 2003). Here, we re-examine this scenario with the aim of clarifying the interrelationships that exist between the different solutions, and in this way, (...) produce a global vision of the problem. We propose to investigate the different expressions for evaluating the value of the evidence by using a graphical approach, i.e. Bayesian networks, to model the rationale behind each of the proposed solutions and the assumptions made on the unknown parameters in this problem. (shrink)

Modelling reasoning with legal cases has been a central concern of AI and Law since the 1980s. The approach which represents cases as factors and dimensions has been a central part of that work. In this paper I consider how several varieties of the approach can be applied to the interesting case of Popov v Hayashi. After briefly reviewing some of the key landmarks of the approach, the case is represented in terms of factors and dimensions, and further explored using (...) theory construction and argumentation schemes approaches. (shrink)

Fifty years of effort in artificial intelligence (AI) and the formalization of legal reasoning have produced both successes and failures. Considerable success in organizing and displaying evidence and its interrelationships has been accompanied by failure to achieve the original ambition of AI as applied to law: fully automated legal decision-making. The obstacles to formalizing legal reasoning have proved to be the same ones that make the formalization of commonsense reasoning so difficult, and are most evident where legal reasoning has to (...) meld with the vast web of ordinary human knowledge of the world. Underlying many of the problems is the mismatch between the discreteness of symbol manipulation and the continuous nature of imprecise natural language, of degrees of similarity and analogy, and of probabilities. (shrink)

Carneades is an open source argument mapping application and a programming library for building argumentation support tools. In this paper, Carneades’ support for argument reconstruction, evaluation and visualization is illustrated by modeling most of the factual and legal arguments in Popov v Hayashi.

In 'A Constitution of Many Minds' Cass Sunstein argues that the three major approaches to constitutional interpretation – Traditionalism, Populism and Cosmopolitanism – all rely on some variation of a ‘many-minds’ argument. Here we assess each of these claims through the lens of the Condorcet Jury Theorem. In regard to the first two approaches we explore the implications of sequential influence among courts (past and foreign, respectively). In regard to the Populist approach, we consider the influence of opinion leaders.

This paper examines the deontic logic of the Talmud. We shall find, by looking at examples, that at first approximation we need deontic logic with several connectives: O T A Talmudic obligation F T A Talmudic prohibition F D A Standard deontic prohibition O D A Standard deontic obligation. In classical logic one would have expected that deontic obligation O D is definable by $O_DA \equiv F_D\neg A$ and that O T and F T are connected by $O_TA \equiv F_T\neg (...) A$ This is not the case in the Talmud for the T (Talmudic) operators, though it does hold for the D operators. We must change our underlying logic. We have to regard {O T , F T } and {O D , F D } as two sets of operators, where O T and F T are independent of one another and where we have some connections between the two sets. We shall list the types of obligation patterns appearing in the Talmud and develop an intuitionistic deontic logic to accommodate them. We shall compare Talmudic deontic logic with modern deontic logic. (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)

In patent law most of the crucial legal questions such as patentability and infringement are linked to the patent claims. The European Patent Office regards patent claims as a set of independent features which are examined separately in a more or less formal way. The author has found that this approach allows for developing a simple mathematical model which treats patent claim features as logical statements and patent claims as compound statements wherein the individual statements are connected by logical connectives. (...) The proposed mathematical model provides a uniform system for examining various legal questions that are dealt with separately under current case law, moreover, it allows for developing an expert system for resolving complex legal situations and for automating the evaluation of a large number of patent claim variants that is currently not possible. (shrink)

This paper studies the use of hypothetical and value-based reasoning in US Supreme-Court cases concerning the United States Fourth Amendment. Drawing upon formal AI & Law models of legal argument a semi-formal reconstruction is given of parts of the Carney case, which has been studied previously in AI & law research on case-based reasoning. As part of the reconstruction, a semi-formal proposal is made for extending the formal AI & Law models with forms of metalevel reasoning in several argument schemes. (...) The result is compared with Rissland’s (1989) analysis in terms of dimensions and Ashley’s (2008) analysis in terms of his process model of legal argument with hypotheticals. (shrink)

Uses erotetic logic to model the courtroom objection "Asked and Answered!".

We present an argument-based formalism of contract dispute resolution following a modern view that the court would resolve a contract dispute by enforcing an interpretation of contract that reasonably represents the mutual intention of contract parties. Legal doctrines provide principles, rules and guidelines for the court to objectively arrive at such an interpretation. In this paper, we establish the appropriateness of the formalism by applying it to resolve disputes about performance relief with the legal doctrines of impossibility and frustration of (...) purpose in common laws of contract. The formalism is based on modular argumentation, a recently proposed extension of assumption-based argumentation for modelling contract dispute resolution. (shrink)

Presumption is a complex concept in law, affecting the dialogue setting. However, it is not clear how presumptions work in everyday argumentation, in which the concept of “plausible argumentation” seems to encompass all kinds of inferences. By analyzing the legal notion of presumption, it appears that this type of reasoning combines argument schemes with reasoning from ignorance. Presumptive reasoning can be considered a particular form of reasoning, which needs positive or negative evidence to carry a probative weight on the conclusion. (...) For this reason, presumptions shift the burden of providing evidence or explanations onto the interlocutor. The latter can provide new information or fail to do so: whereas in the first case the new information rebuts the presumption, in the second case, the absence of information that the interlocutor could reasonably provide strengthen the conclusion of the presumptive reasoning. In both cases the result of the presumption is to strengthen the conclusion of the reasoning from lack of evidence. As shown in the legal cases, the effect of presumption is to shift the burden of proof to the interlocutor; however, the shift a presumption effects is only the shift of the evidential burden, or the burden of completing the incomplete knowledge from which the conclusion was drawn. The burden of persuasion remains on the proponent of the presumption. On the contrary, reasoning from definition in law is a conclusive proof, and shifts to the other party the burden to prove the contrary. This crucial difference can be applied to everyday argumentation: natural arguments can be divided into dialectical and presumptive arguments, leading to conclusions materially different in strength. -/- . (shrink)

Concepts as reasonable doubt, cognitive biases and emotions are now a theoretical problem for the practice of law, and the law understood as legal argumentation. From a theoretical point of view, the screenplay written by Reginald Rose, Twelve Angry Men, is an outstanding example to analyze some of these concepts, and its influence on procedural stage. Cognitive biases and informal fallacies are theoretical challenge to legal argumentation.

To create a programming environment for contract dispute resolution, we propose an extension of assumption-based argumentation into modular assumption-based argumentation in which different modules of argumentation representing different knowledge bases for reasoning about beliefs and facts and for representation and reasoning with the legal doctrines could be built and assembled together. A distinct novel feature of modular argumentation in compare with other modular logic-based systems like Prolog is that it allows references to different semantics in the same module at the (...) same time, a feature critically important for application of argumentation in legal domains like contract dispute resolution where the outcomes of court cases often depend on whether credulous or skeptical modes of reasoning were applied by the contract parties. We apply the new framework to model the doctrines of contract breach and mutual mistake. (shrink)

Based on the paradigm of Constructive Descriptions and Situations, we introduce NIC, an ontology of social collectives that includes social agents, plans, norms, and the conceptual relations between them. Norms are distinguished from plans, and their relations are formalized. A typology of social collectives is also proposed, including collection of agents, knowledge community, intentional collective, and normative intentional collective. NIC, represented as a first-order theory as well as a description logic for applications requiring automated reasoning, provides the expressivity to talk (...) about the contexts (social, informational, circumstantial, and conceptual), in which collectives make and produce sense within the interplay of plans and norms. (shrink)

This paper is a preliminary investigation into the application of the formal-logical theory of normative positions to the characterisation of normative-informational positions, pertaining to rules that are meant to regulate the supply of information. First, we present the proposed framework. Next, we identify the kinds of nuances and distinctions that can be articulated in such a logical framework. Finally, we show how such nuances can arise in specific regulations. Reference is made to Data Protection Law and Contract Law, among others. (...) The proposed approach is articulated around two essential steps. The first involves identifying the set of possible interpretations that can be given to a particular norm. This is done by using formal methods. The second involves picking out one of these interpretations as the most likely one. This second step can be resolved only by using further information (e.g., the context or other parts of the regulation). (shrink)

This article presents a formal dialogue game for adjudication dialogues. Existing AI & law models of legal dialogues and argumentation-theoretic models of persuasion are extended with a neutral third party, to give a more realistic account of the adjudicator’s role in legal procedures. The main feature of the model is a division into an argumentation phase, where the adversaries plea their case and the adjudicator has a largely mediating role, and a decision phase, where the adjudicator decides the dispute on (...) the basis of the claims, arguments and evidence put forward in the argumentation phase. The model allows for explicit decisions on admissibility of evidence and burden of proof by the adjudicator in the argumentation phase. Adjudication is modelled as putting forward arguments, in particular undercutting and priority arguments, in the decision phase. The model reconciles logical aspects of burden of proof induced by the defeasible nature of arguments with dialogical aspects of burden of proof as something that can be allocated by explicit decisions on legal grounds. (shrink)

This paper presents a formal reconstruction of a Dutch civil legal case in Prakken’s formal model of adjudication dialogues. The object of formalisation is the argumentative speech acts exchanged during the dispute by the adversaries and the judge. The goal of this formalisation is twofold: to test whether AI & law models of legal dialogues in general, and Prakken’s model in particular, are suitable for modelling particular legal procedures; and to learn about the process of formalising an actual legal dispute.

In this paper we describe an approach to practical reasoning, reasoning about what it is best for a particular agent to do in a given situation, based on presumptive justifications of action through the instantiation of an argument scheme, which is then subject to examination through a series of critical questions. We identify three particular aspects of practical reasoning which distinguish it from theoretical reasoning. We next provide an argument scheme and an associated set of critical questions which is able (...) to capture these features. In order that both the argument scheme and the critical questions can be given precise interpretations we use the semantic structure of an Action-Based Alternating Transition System as the basis for their definition. We then work through a detailed example to show how this approach to practical reasoning can be applied to a problem solving situation, and briefly describe some other previous applications of the general approach. In a second example we relate our account to the social laws paradigm for co-ordinating multi-agent systems. The contribution of the paper is to provide firm foundations for an approach to practical reasoning based on presumptive argument in terms of a well-known model for representing the effects of actions of a group of agents. (shrink)

In order to improve the management of copyright in the Internet, known as Digital Rights Management, there is the need for a shared language for copyright representation. Current approaches are based on purely syntactic solutions, i.e. a grammar that defines a rights expression language. These languages are difficult to put into practise due to the lack of explicit semantics that facilitate its implementation. Moreover, they are simple from the legal point of view because they are intended just to model the (...) usage licenses granted by content providers to end-users. Thus, they ignore the copyright framework that lies behind and the whole value chain from creators to end-users. Our proposal is to use a semantic approach based on semantic web ontologies. We detail the development of a copyright ontology in order to put this approach into practice. It models the copyright core concepts for creation, rights and the basic kinds of actions that operate on content. Altogether, it allows building a copyright framework for the complete value chain. The set of actions operating on content are our smaller building blocks in order to cope with the complexity of copyright value chains and statements and, at the same time, guarantee a high level of interoperability and evolvability. The resulting copyright modelling framework is flexible and complete enough to model many copyright scenarios, not just those related to the economic exploitation of content. The ontology also includes moral rights, so it is possible to model this kind of situations as it is shown in the included example model for a withdrawal scenario. Finally, the ontology design and the selection of tools result in a straightforward implementation. Description Logic reasoners are used for license checking and retrieval. Rights are modelled as classes of actions, action patterns are modelled also as classes and the same is done for concrete actions. Then, to check if some right or license grants an action is reduced to check for class subsumption, which is a direct functionality of these reasoners. (shrink)

We present a formal, mathematical model of argument structure and evaluation, taking seriously the procedural and dialogical aspects of argumentation. The model applies proof standards to determine the acceptability of statements on an issue-by-issue basis. The model uses different types of premises (ordinary premises, assumptions and exceptions) and information about the dialectical status of statements (stated, questioned, accepted or rejected) to allow the burden of proof to be allocated to the proponent or the respondent, as appropriate, for each premise separately. (...) Our approach allows the burden of proof for a premise to be assigned to a different party than the one who has the burden of proving the conclusion of the argument, and also to change the burden of proof or applicable proof standard as the dialogue progresses from stage to stage. Useful for modeling legal dialogues, the burden of production and burden of persuasion can be handled separately, with a different responsible party and applicable proof standard for each. Carneades enables critical questions of argumentation schemes to be modeled as additional premises, using premise types to capture the varying effect on the burden of proof of different kinds of questions. (shrink)

An application of Narrative Knowledge Representation Language (NKRL) techniques on (declassified) ‘terrorism in Southern Philippines’ documents has been carried out in the context of the IST Parmenides project. This paper describes some aspects of this work: it is our belief, in fact, that the Knowledge Representation techniques and the Intelligent Information Retrieval tools used in this experiment can be of some interest also in an ‘Ontological Modelling of Legal Events and Legal Reasoning’ context.

When a conflict of duties arises, a resolution is often sought by use of an ordering of priority or importance. This paper examines how such a conflict resolution works, compares mechanisms that have been proposed in the literature, and gives preference to one developed by Brewka and Nebel. I distinguish between two cases – that some conflicts may remain unresolved, and that a priority ordering can be determined that resolves all – and provide semantics and axiomatic systems for accordingly defined (...) dyadic deontic operators. (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)

In this paper it is shown how tools developed in argumentation theory and artificial intelligence can be applied to the development of a new dialectical analysis of the speech act of making a proposal in a deliberation dialogue. These tools are developed, modified and used to formulate dialogue pre-conditions, defining conditions and post-conditions for the speech act of making a proposal in a deliberation dialogue. The defining conditions set out what is required for a move in a dialogue to count (...) as the making of a proposal by one of the parties. What is required are the conditions that (1) the move fit the requirements of the argumentation scheme for practical reasoning, and (2) the premises are propositions describing common goals of both parties or propositions that they reasonably consider means to achieve these goals. The analysis goes beyond the standard speech act approach by specifying not only the normative requirements for making a well-formed proposal, but also the requirements for responding to it by questioning or criticizing it, and the requirements for defending it. (shrink)

In recent years several proposals to view reasoning with legal cases as theory construction have been advanced. The most detailed of these is that of Bench-Capon and Sartor, which uses facts, rules, values and preferences to build a theory designed to explain the decisions in a set of cases. In this paper we describe CATE (CAse Theory Editor), a tool intended to support the construction of theories as described by Bench-Capon and Sartor, and which produces executable code corresponding to a (...) theory. CATE has been used in a series of experiments intended to explore a number of issues relating to such theories, including how the theories should be constructed, how sets of values should be compared, and the representation of cases using structured values as opposed to factors. (shrink)

In this paper we describe AGATHA, a program designed to automate the process of theory construction in case based domains. Given a seed case and a number of precedent cases, the program uses a set of argument moves to generate a search space for a dialogue between the parties to the dispute. Each move is associated with a set of theory constructors, and thus each point in the space can be associated with a theory intended to explain the seed case (...) and the other cases in the domain. The space is large and so an heuristic search method is needed. This paper describes two methods based on A* and alpha/beta pruning and also a series of experiments designed to explore the appropriateness of different evaluation functions, the most useful precedents to use as seed cases and the quality of the resulting theories. (shrink)

The analysis of how social conventions emerge and become established is rightly viewed as a significant study of great relevance to models of legal and social systems. Such conventions, however, do not operate in a monotonic fashion, i.e. the fact that a convention is recognised and complied with at some instant is no guarantee it will continue to be so indefinitely. In total rules and protocols may evolve, with or without the consent of individual members of the society, even to (...) the extent that some cease to be observed or effective. In this paper we examine a framework for examining such changes in behavioural conventions that uses a proposed “taxonomy of social conventions” as the basis of a qualitative model deriving from value-based argument systems. (shrink)

This paper argues the thesis that a particular style of reasoning, qualitative comparative reasoning (QCR), plays a role in at least three areas of legal reasoning that are central in AI and law research, namely legal theory construction, case-based reasoning in the form of case comparison, and legal proof. The paper gives an informal exposition of one particular way to deal with QCR, based on the author’s previous work on reason-based logic (RBL). Then it contains a substantially adapted formalisation of (...) RBL, to make RBL suitable for dealing with QCR. The paper concludes with a brief discussion of related work. (shrink)