Proponents of strict rule-based theories of judicial reasoning in common-law systems have offered a number of criticisms of analogical alternatives. I explain these criticisms and show that at best they apply equally well to rule-based theories. Further, I show how the analogical theories explain a feature of judicial common-law reasoningthat rule-based theories ignore. Finally, I show that reason-based, analogical theories of common-law judicial reasoning, such as those offered by John Horty and Grant Lamond, offer especially strong rejoinders to the rule-theorist (...) objections and persuasive accounts of distinguishing. (shrink)

This article argues that legal precedents do not create rules, but rather create a special type of reason in favour of a decision in later cases. Precedents are often argued to be analogous to statutes in their law-creating function, but the common law practice of distinguishing is difficult to reconcile with orthodox accounts of the function of rules. Instead, a precedent amounts to a decision on the balance of reasons in the case before the precedent court, and later courts are (...) required to decide cases on the basis that the earlier decision was correctly decided. (shrink)

This paper describes one way in which a precise reason model of precedent could be developed, based on the general idea that courts are constrained to reach a decision that is consistent with the assessment of the balance of reasons made in relevant earlier decisions. The account provided here has the additional advantage of showing how this reason model can be reconciled with the traditional idea that precedential constraint involves rules, as long as these rules are taken to be defeasible. (...) The account presented is firmly based on a body of work that has emerged in AI and Law. This work is discussed, and there is a particular discussion of approaches based on theory construction, and how that work relates to the model described in this paper. (shrink)

What is law (and why should we care)? -- Crazy little thing called "law" -- Austin's sanction theory -- Hart and the rule of recognition -- How to do things with plans -- The making of a legal system -- What law is -- Legal reasoning and judicial decision making -- Hard cases -- Theoretical disagreements -- Dworkin and distrust -- The economy of trust -- The interpretation of plans -- The value of legality.

The main purpose of this paper is to explore the role played by logic in the legal domain. In the traditional conception which underlies the movement of codification, judges are able to find in the legal system (the Master System) a unique answer for every legal problem. This entails its completeness, consistency and the possibility of deriving from it the contents of all judicial decisions. Although the ideal model of this conception is supported by important theoretical and political ideals, it (...) has significant shortcomings. The elements of normative systems (Master Systems) are “norms” and not mere “norm-formulations.” A “norm” is the meaning attributed to normative linguistic expressions. The set of all normative expressions, such as statutes, codes, etc. forms what is called the Master Book. One of the main problems for the ideal model is the identification of a normative system behind the Master Book. Interpretative arguments are the tools designed to solve these problems. Although the requirements of the model are not totally fulfilled in actual practice, it remains as an effective ideal rational goal behind legal activities linked to adjudication and most theoretical approaches to law. (shrink)

I LAW AND NATURE i. The "Pure" Theory The Pure Theory of Law is a theory of positive law. It is a theory of positive law in general, not of a specific legal ...

The doctrine of precedent, as it has evolved within the common law, has at its heart a form of reasoning—broadly speaking, alogic—according to which the decisions of earlier courts in particular cases somehow generalize to constrain the decisions of later courts facing different cases, while still allowing these later courts a degree of freedom in responding to fresh circumstances. Although the techniques for arguing on the basis of precedent are taught early on in law schools, mastered with relative ease, and (...) applied on a daily basis by legal practitioners, it has proved to be considerably more difficult to arrive at a theoretical understanding of the doctrine itself—a clear articulation of the underlying logic. (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 dissertation develops, justifies, and examines the jurisprudential implications of a non-monotonic theory of common law legal reasoning. Legal rules seem to have exceptions but identifying all of them is difficult. This hinders attempts to formalize legal rules using classical logics. Non-monotonic logics allow defeasible inference, permitting rules that hold generally but can be defeated in the presence of exceptions. This ameliorates the problem of characterizing all exceptions to a rule, because exceptions can be added piecemeal while the rule remains. (...) The first portion of the dissertation rebuts a prominent criticism leveled at a large class of theories of legal reasoning that includes my theory. The charge is that no coherent theory can recognize both the difference between distinguishing and overruling, and the constraint of precedent. The critics argue that is more important than and that can only be explained by monotonic legal rules. Drawing on cognitive psychology as well as legal theory, I show that coherent theories, such as my own, can accommodate both and. The second chapter provides motivation for understanding precedential constraint in terms of non-monotonic default rules and introduces my positive theory, which elaborates on John Horty's work in treating legal rules as prioritized defaults involving reasons. I motivate and implement a relaxation of Horty's restrictions on the form of rules to allow a more fine-grained characterization of precedent. Finally, I explore the relationship between these relaxations and the concept of precedent. The final section explains how my theory fits into the traditional jurisprudential ecosystem. I demonstrate that, contrary to assertions in the legal theory literature, this non-monotonic approach is entirely compatible with positivism's commitment to extracting rules from authoritative legal sources, namely court opinions. I also suggest how it might be attractive to law and economics theorists, pragmatists, and followers of Dworkin. (shrink)

The goal of this paper is to frame a theory of reasons--what they are, how they support actions or conclusions--using the tools of default logic. After sketching the basic account of reasons as provided by defaults, I show how it can be elaborated to deal with two more complicated issues: first, situations in which the priority relation among defaults, and so reasons as well, is itself established through default reasoning; second, the treatment of undercutting defeat and exclusionary reasons. Finally, and (...) by way of application, I show how the resulting account can shed some light on Jonathan Dancy's argument from reason holism to a form of extreme particularism in moral theory. (shrink)

Demystifying Legal Reasoning defends the proposition that there are no special forms of reasoning peculiar to law. Legal decision makers engage in the same modes of reasoning that all actors use in deciding what to do: open-ended moral reasoning, empirical reasoning, and deduction from authoritative rules. This book addresses common law reasoning when prior judicial decisions determine the law, and interpretation of texts. In both areas, the popular view that legal decision makers practise special forms of reasoning is false.

The result model of precedent holds that a legal precedent controls a fortiori cases—those cases, that is, that are at least as strong for the winning side of the precedent as the precedent case itself. This paper defends the result model against some objections by Larry Alexander, drawing on ideas from the field of Artificial Intelligence and Law in order to define an appropriate strength ordering for cases.

Reasoning with cases has been a primary focus of those working in AI and law who have attempted to model legal reasoning. In this paper we put forward a formal model of reasoning with cases which captures many of the insights from that previous work. We begin by stating our view of reasoning with cases as a process of constructing, evaluating and applying a theory. Central to our model is a view of the relationship between cases, rules based on cases, (...) and the social values which justify those rules. Having given our view of these relationships, we present our formal model of them, and explain how theories can be constructed, compared and evaluated. We then show how previous work can be described in terms of our model, and discuss extensions to the basic model to accommodate particular features of previous work. We conclude by identifying some directions for future work. (shrink)

In this book the author gives a broad overview of different areas of research in nonmonotonic reasoning, and presents some new results and ideas based on his research. The guiding principles are: clarification of the different research activities in the area, which have sometimes been undertaken independently of each other; and appreciation of the fact that these research activities often represent different means to the same ends, namely sound theoretical foundations and efficient computation. The book begins with a discussion of (...) the various types of nonmonotonic reasoning, their applications and their logics. Theorem proving techniques for these logics are also described. The following chapters deal with formulations of nonmonotonic inheritance, and nonmonotonic reasoning based on nonmonotonic rules. The final chapter discusses the achievements in the field in the light of the Yale shooting example. The book will be welcomed by researchers in theoretical computer science and artificial intelligence. (shrink)

This paper introduces a generalization of Reiter’s notion of “extension” for default logic. The main difference from the original version mainly lies in the way conflicts among defaults are handled: in particular, this notion of “general extension” allows defaults not explicitly triggered to pre-empt other defaults. A consequence of the adoption of such a notion of extension is that the collection of all the general extensions of a default theory turns out to have a nontrivial algebraic structure. This fact has (...) two major technical fall-outs: first, it turns out that every default theory has a general extension; second, general extensions allow one to define a well-behaved, skeptical relation of defeasible consequence for default theories, satisfying the principles of Reflexivity, Cut, and Cautious Monotonicity formulated by D. Gabbay. (shrink)

A logic-based approach to the design of computing systems would, undoubtedly, offer many advantages over the imperative paradigm most commonly applied so far for programming and hardware design and, consequently, logic, again and again, has been heralded as the basis for the next generation of computer systems. While logic and formal methods are indeed gaining ground in many areas of computer science and artificial intelligence the expected revolution has not yet happened. In this book the author offers a convincing solution (...) to the ramification problem and qualification problem associated with the frame problem and thus contributes to a satisfactory solution of the core problem and related challenges. Thielscher bases his approach on the fluent calculus, a first-order Prolog-like formalism allowing for the description of actions and change. (shrink)