Taking into account one of the meanings of the expression binding precedent and stipulating a definition for that meaning, this article aims to contribute to the concept's structural characterization. By this I mean the effort to identify the legal norms on which the existence and functioning of binding precedents depend and to show that these norms constitute a group of Hohfeldian legal relations between the courts whose precedents must be followed, the courts that must follow them, and the individuals whose (...) legal situations are as a result modified by the observance and the breach of those precedents. (shrink)

In this article I argue for rule-based, non-monotonic theories of common law judicial reasoning and improve upon one such theory offered by Horty and Bench-Capon. The improvements reveal some of the interconnections between formal theories of judicial reasoning and traditional issues within jurisprudence regarding the notions of the ratio decidendi and obiter dicta. Though I do not purport to resolve the long-standing jurisprudential issues here, it is beneficial for theorists both of legal philosophy and formalizing legal reasoning to see where (...) the two projects interact. (shrink)

ABSTRACTLegal reasoning is commonly thought of as being based on either rules or analogies. More specifically, there is ongoing debate regarding whether precedential reasoning is best characterized as rule-based or analogical. This article continues that work by comparing recent and representative approaches from each camp, namely, Stevens's analogical model and the “rule-based” model of Horty and Rigoni. In the course of the comparison improvements on each approach are suggested and the improved models serve as the basis for the ultimate evaluation. (...) The evaluation demonstrates that the “best” approach depends on the goals one has in theorizing legal reasoning as well as the jurisprudential assumptions one is willing to make. (shrink)

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 paper gives an account of dimensions in the reason model found in Horty : 1–33, 2011), Horty and Bench-Capon and Rigoni :133–160, 2015. doi: 10.1007/s10506-015-9166-x). The account is constructed with the purpose of rectifying problems with the approach to incorporating dimensions in Horty, namely, the problems arising from the collapse of the distinction between the reason model and the result model on that approach. Examination of the newly constructed theory revealed that the importance of dimensions in the reason model (...) lies in their ability to establish weighings between reasons/factors of the same polarity. This permits past cases to constrain future cases in ways they could not on the reason model with just factors. The paper then discusses how dimensions might be established from a case base and how dimensions that are incomplete in various aspects might be dealt with in the theory. It closes with comparisons to other work in the literature on AI and Law and suggestions for further improvement of the reason model. (shrink)

This article discusses the desirability and feasibility of modeling precedents with multiple interpretations within factor-based models of precedential constraint. The main idea is that allowing multiple reasonable interpretations of cases and modeling precedential constraint as a function of what all reasonable interpretations compel may be advantageous. The article explains the potential benefits of extending the models in this way with a focus on incorporating a theory of vertical precedent in U.S. federal appellate courts. It also considers the costs of extending (...) the models in this way, such as the significant increase in the functional size of the case base and the need to provide some kind of ordering on interpretations to select a “best” interpretation. Finally, the article suggests partially incorporating multiple interpretations of dimensions as a realistic starting point for incorporating interpretations generally, and shows how doing so can help address difficulties with dimensions. The conclusion remarks on the use of interpretations to deal with inconsistent precedents. (shrink)

The volume analyses and develops David Makinson’s efforts to make classical logic useful outside its most obvious application areas. The book contains chapters that analyse, appraise, or reshape Makinson’s work and chapters that develop themes emerging from his contributions. These are grouped into major areas to which Makinsons has made highly influential contributions and the volume in its entirety is divided into four sections, each devoted to a particular area of logic: belief change, uncertain reasoning, normative systems and the resources (...) of classical logic. Among the contributions included in the volume, one chapter focuses on the “inferential preferential method”, i.e. the combined use of classical logic and mechanisms of preference and choice and provides examples from Makinson’s work in non-monotonic and defeasible reasoning and belief revision. One chapter offers a short autobiography by Makinson which details his discovery of modern logic, his travels across continents and reveals his intellectual encounters and inspirations. The chapter also contains an unusually explicit statement on his views on the role of logic in philosophy. (shrink)

The standard model of precedential constraint holds that a court is equally free to modify a precedent of its own and a precedent of a superior court—overruling aside, it does not differentiate horizontal and vertical precedents. This paper shows that no model can capture the U.S. doctrine of precedent without making that distinction. A precise model is then developed that does just that. This requires situating precedent cases in a formal representation of a hierarchical legal structure, and adjusting the constraint (...) that a precedent imposes based on the relationship of the precedent court and the instant court. The paper closes with suggestions for further improvements of the model. (shrink)

The last two decades have seen a surge of support for normative quietism: most notably, from Dworkin, Nagel, Parfit and Scanlon. Detractors like Enoch and McPherson object that quietism is incompatible with realism about normativity. The resulting debate has stagnated somewhat. In this paper I explore and defend a more promising way of developing that objection: I’ll argue that if normative quietism is true, we can create reasons out of thin air, so normative realists must reject normative quietism.

This paper investigates the process of reasoning through which a judge determines whether a precedent-case gives her a binding reason to follow in her present-case. I review the objections that have been raised against the two main accounts of reasoning by precedent: the rule-account and the analogy-account. I argue that both accounts can be made viable by amending them to meet the objections. Nonetheless, I believe that there is an argument for preferring accounts that integrate analogical reasoning: any account of (...) reasoning by precedent that is descriptively minimally adequate will leave some room for judicial discretion. Discretion should be used under consideration of the best legally relevant arguments for and against a decision. Integrating analogical reasoning helps the judge to bring to her own attention the strongest case for following. Analogical reasoning also eases the recognition of possible reasons for distinguishing. Thereby, it facilitates a more balanced decision-making process. (shrink)

This article models legal interpretation through argumentation and provides a logical analysis of interpretive arguments, their conflicts, and the resulting indeterminacies. Interpretive arguments are modelled as defeasible inferences, which can be challenged and defeated by counterarguments and be reinstated through further arguments. It is shown what claims are possibly (defensibly) or necessarily (justifiably) supported by the arguments constructible from a given interpretive basis, i.e., a set of interpretive canons coupled with reasons for their application. It is finally established under what (...) conditions such arguments provide single outcomes or rather support alternative interpretive conclusions, thus leading to propositions of law whose truth‐value is undetermined. (shrink)

This paper proposes a formal top-level model of explaining the outputs of machine-learning-based decision-making applications and evaluates it experimentally with three data sets. The model draws on AI & law research on argumentation with cases, which models how lawyers draw analogies to past cases and discuss their relevant similarities and differences in terms of relevant factors and dimensions in the problem domain. A case-based approach is natural since the input data of machine-learning applications can be seen as cases. While the (...) approach is motivated by legal decision making, it also applies to other kinds of decision making, such as commercial decisions about loan applications or employee hiring, as long as the outcome is binary and the input conforms to this paper’s factor- or dimension format. The model is top-level in that it can be extended with more refined accounts of similarities and differences between cases. It is shown to overcome several limitations of similar argumentation-based explanation models, which only have binary features and do not represent the tendency of features towards particular outcomes. The results of the experimental evaluation studies indicate that the model may be feasible in practice, but that further development and experimentation is needed to confirm its usefulness as an explanation model. Main challenges here are selecting from a large number of possible explanations, reducing the number of features in the explanations and adding more meaningful information to them. It also remains to be investigated how suitable our approach is for explaining non-linear models. (shrink)

In this paper several recent factor- and dimension-based models of precedential constraint are formally investigated and an alternative dimension-based model is proposed. Simple factor- and dimension-based syntactic criteria are identified for checking whether a decision in a new case is forced, in terms of the relevant differences between a precedent and a new case, and the difference between absence of factors and negated factors in factor-based models is investigated. Then Horty’s and Rigoni’s recent dimension-based models of precedential constraint are critically (...) examined. An alternative to their reason models is proposed which is less expressive but arguably easier to apply in practice. (shrink)

In the court of law, a person can be punished for attempting to commit a crime. An open issue in the study of Artificial Intelligence and Law is whether the law of attempts could be formally modelled. There are distinct legal rules for determining attempted crime whereas the last-act rule (also called proximity rule) represents the strictest approach. In this paper, we provide a formal model of the last-act rule using structured argumentation.

Courts in common law systems decide cases as they decided like cases in the past—even if they believe they decided those past cases wrongly. What, if anything, justifies this practice? I defend two main claims. The first is that fairness favors treating like cases alike if that means treating them correctly. The second is that, in general, a court is as likely to decide an instant case correctly as it was to decide a previous and like case correctly. Together, these (...) claims tell us that departing from and following precedent are equally likely to yield a correct decision, whereas following precedent may also yield a fair decision. Adhering to precedent is the dominant alternative, as a result. Fairness therefore justifies the practice of precedent. While this conclusion is not original, my argument for it is. (shrink)

The article considers two different interpretations of the reason model of precedent pioneered by John Horty. On a plausible interpretation of the reason model, past cases provide reasons to prioritize reasons favouring the same outcome as a past case over reasons favouring the opposing outcome. Here I consider the merits of this approach to the role of precedent in legal reasoning in comparison with a closely related view favoured by some legal theorists, according to which past cases provide reasons for (...) undercutting (or ‘excluding’) reasons favouring the opposing outcome. After embedding both accounts within a general default logic, I note some important differences between the two approaches that emerge as a result of plausible distinctions between rebutting and undercutting defeat in formal models of legal reasoning. These differences stem from the ‘preference independence’ of undercutting defeat. Undercutting reasons succeed in defeating opposing reasons irrespective of their relative strength. As a result, the two accounts differ in their account of the way in which precedents constrain judicial reasoning. I conclude by suggesting that the two approaches can be integrated within a single model, in which the distinction between undercutting and rebutting defeat is used to account for the distinction between strict and persuasive forms of precedential constraint. (shrink)

ABSTRACTAccording to the prioritized reason model of precedent, precedential constraint is explained in terms of the need for decision-makers to reconcile their decisions with a settled priority order extracted from past cases. The prioritized reason model of precedent departs from the view that common law rules comprise protected reasons for action. In this article I show that a model utilizing protected reasons and the prioritized reason model of precedential constraint are, in an important sense, equivalent. I then offer some reflections (...) on the philosophical significance of this result. I argue that the protected reason model is consistent with the phenomenology of precedential constraint. I suggest an account of precedential reasoning that reconciles the prioritized reason and protected reason models. (shrink)

This paper shows how two models of precedential constraint can be broadened to include legal information represented through dimensions. I begin by describing a standard representation of legal cases based on boolean factors alone, and then reviewing two models of constraint developed within this standard setting. The first is the “result model”, supporting only a fortiori reasoning. The second is the “reason model”, supporting a richer notion of constraint, since it allows the reasons behind a court’s decisions to be taken (...) into account. I then show how the initial representation can be modified to incorporate dimensional information and how the result and reason models can be adapted to this new dimensional setting. As it turns out, these two models of constraint, which are distinct in the standard setting, coincide once they are transposed to the new dimensional setting, yielding exactly the same patterns of constraint. I therefore explore two ways of refining the reason model of constraint so that, even in the dimensional setting, it can still be separated from the result model. (shrink)

In previous work, I showed how the “reason model” of precedential constraint could naturally be generalized from the standard setting in which it was first developed to a richer setting in which dimensional information is represented as well. Surprisingly, it then turned out that, in this new dimensional setting, the reason model of constraint collapsed into the “result model,” which supports only a fortiori reasoning. The purpose of this note is to suggest a modification of the reason model of constraint (...) that distinguishes it from the result model even in the dimensional setting. (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)

Hume’s Law that one cannot derive an “ought” from an “is” has often been deemed to bear a significance that extends far beyond logic. Repeatedly, it has been invoked as posing a serious threat to views about normativity: naturalism in metaethics and positivism in jurisprudence. Yet in recent years, a puzzling asymmetry has emerged: while the view that Hume’s Law threatens naturalism has largely been abandoned (due mostly to Pigden’s work, see e.g. Pigden 1989), the thought that Hume’s Law is (...) a serious challenge to positivism has only grown in prominence. Our main aim is to establish that Hume’s Law is not a threat to positivism or naturalism. First, we connect extensive, but unfortunately siloed, discussions of this issue. Second, we show that Hume’s Law is not a serious threat to naturalism or positivism, for the gap between logic and such theses is very hard to bridge in a way that would make Hume’s Law able to bear this significance. Finally, we emphasize an implication of our discussion: it undermines one of the main “dialectical tributaries” in jurisprudence (Toh 2018). (shrink)

This paper attempts to formalize the differences between two methods of analysis used by judicial opinions in common law jurisdictions to contradict holdings posited by earlier opinions: “disagreeing” with the holdings of the earlier opinions and “attributing” holdings to the prior opinions. The paper will demonstrate that it is necessary to model both methods of analysis differently to generate an accurate picture of the state of legal authority in hypothetical examples, as well as in an example based on Barry Friedman’s (...) analysis of the “stealth overruling” of Miranda v. Arizona through subsequent judicial interpretations. Because the question of whether “disagreement” and “attribution” need to be modeled separately relates to contradictions rather than to subtler interactions between holdings such as “distinguishing,” it can be answered using the simple technique of modeling holdings as propositional variables and evaluating the holdings using truth tables. (shrink)

Computational models of legal precedent-based reasoning developed in AI and Law are typically based on the simplifying assumption that the background set of precedent cases is consistent. Besides being unrealistic in the legal domain, this assumption is problematic for recent promising applications of these models to the development of explainable AI methods. In this paper I explore a model of legal precedent-based reasoning that, unlike existing models, does not rely on the assumption that the background set of precedent cases is (...) consistent. The model is a generalization of the reason model of precedential constraint. I first show that the model supports an interesting deontic logic, where consistent obligations can be derived from inconsistent case bases. I then provide an explanation of this surprising result by proposing a reformulation of the model in terms of cases that support a new potential decision and cases that conflict with it. Finally, I show that the reformulation of the model allows us to verify that inconsistent case bases do not make verification that a decision is permissible substantially more complex than consistent case bases and to introduce intuitive criteria to compare different permissible decisions. (shrink)

This paper is an introduction to a virtual special issue of AI and Law exploring the legacy of the influential HYPO system of Rissland and Ashley. The papers included are: Arguments and cases: An inevitable intertwining, BankXX: Supporting legal arguments through heuristic retrieval, Modelling reasoning with precedents in a formal dialogue Game, A note on dimensions and factors, An empirical investigation of reasoning with legal cases through theory construction and application, Automatically classifying case texts and predicting outcomes, A factor-based definition (...) of precedential constraint and An improved factor based approach to precedential constraint. After describing HYPO, in this introduction to the special issue I look at various aspects of its influence on AI and Law: the developments led by Rissland at Amherst; the developments led by Ashley in Pittsburgh; the expression of these ideas in terms of rule based systems, and their subsequent formalisation; value based theories, which were inspired by a critique of HYPO; and contemporary approaches which revive the idea of dimensions. (shrink)

Modern belief revision theory is based to a large extent on partial meet contraction that was introduced in the seminal article by Carlos Alchourrón, Peter Gärdenfors, and David Makinson that appeared in 1985. In the same year, Alchourrón and Makinson published a significantly different approach to the same problem, called safe contraction. Since then, safe contraction has received much less attention than partial meet contraction. The present paper summarizes the current state of knowledge on safe contraction, provides some new results (...) and offers a list of unsolved problems that are in need of investigation. (shrink)