Toulmin’s scheme for the layout of arguments (1958, The Uses of Argument, Cambridge University Press, Cambridge) represents an influential tool for the analysis of arguments. The scheme enriches the traditional premises-conclusion model of arguments by distinguishing additional elements, like warrant, backing and rebuttal. The present paper contains a formal elaboration of Toulmin’s scheme, and extends it with a treatment of the formal evaluation of Toulmin-style arguments, which Toulmin did not discuss at all. Arguments are evaluated in terms of a so-called (...) dialectical interpretation of their assumptions. In such an interpretation, an argument’s assumptions can be evaluated as defeated, e.g., when there is a defeating reason against the assumption. The present work builds on recent research on defeasible argumentation (cf. e.g. the work of Pollock, Reiter, Loui, Vreeswijk, Prakken, Hage and Dung). More specifically, the author’s work on the dialectical logic DEFLOG and the argumentation tool ARGUMED serve as starting points. (shrink)

Dialogues and dialectics have come to playan important role in the field of ArtificialIntelligence and Law. This paper describes thelegal-theoretical and logical background of this role,and discusses the different services into whichdialogues are put. These services include:characterising logical operators, modelling thedefeasibility of legal reasoning, providing the basisfor legal justification and identifying legal issues,and establishing the law in concrete cases. Specialattention is given to the requirements oflaw-establishing dialogues.

The first issue of _Artificial Intelligence and Law_ journal was published in 1992. This paper discusses several topics that relate more naturally to groups of papers than a single paper published in the journal: ontologies, reasoning about evidence, the various contributions of Douglas Walton, and the practical application of the techniques of AI and Law.

I shall compare two views of legal concepts: as nodes in inferential nets and as categories in an ontology (a conceptual architecture). Firstly, I shall introduce the inferential approach, consider its implications, and distinguish the mere possession of an inferentially defined concept from the belief in the concept’s applicability, which also involves the acceptance of the concept’s constitutive inferences. For making this distinction, the inferential and eliminative analysis of legal concepts proposed by Alf Ross will be connected to the views (...) on theoretical concepts in science advanced by Frank Ramsey and Rudolf Carnap. Consequently, the mere comprehension of a legal concept will be distinguished from the application of the concept to a particular legal system, since application presupposes a doctrinal commitment, namely, the belief that the inferences constituting the concept hold in that system. Then, I shall consider how concepts can be characterised by defining the corresponding terms and placing them within an ontology. Finally, I shall argue that there is a tension between the inferential and the ontological approach, but that both need to be taken into account, to capture the meaning and the cognitive function of legal concepts. (shrink)

The paper consists of three parts. In the first part five kinds of defeasibility are distinguished that is ontological, conceptual, epistemic, justification and logical defeasibility. In the second part it is argued that from these, justification defeat is the phenomenon that plays a role in legal reasoning. In the third part, the view is defended that non-monotonic logics are not necessary to model justification defeat, but that they are so to speak the natural way to model this phenomenon.

This paper deals with two issues in the field of reasoning by analogy in the law. The one issue is whether there exists such a thing as analogous rule application, or whether there is only the ‘normal’ application of a broadened rule. It is argued that if rules, as the entities made by a legislator, are distinguished from generalised solutions for cases, the idea of analogous application of rules makes sense. It is also shown how the so-called ‘reason-based model of (...) rule application’, in contrast to the traditional modus ponens or subsumption model, makes it easy to give a logical account of analogous rule application. The other issue is how to argue logically about whether two cases are sufficiently similar to adopt the outcome of the one case for the other case. Section 3 provides a general logical model to establish this. The model is based on the comparison of the reasons for and against a particular solution in the two cases. (shrink)

This paper describes an approach to legal logic based on the formal analysis of argumentation schemes. Argumentation schemes a notion borrowed from the .eld of argumentation theory - are a kind of generalized rules of inference, in the sense that they express that given certain premises a particular conclusion can be drawn. However, argumentation schemes need not concern strict, abstract, necessarily valid patterns of reasoning, but can be defeasible, concrete and contingently valid, i.e., valid in certain contexts or under certain (...) circumstances. A method is presented to analyze argumentation schemes and it is shown how argumentation schemes can be embedded in a formal model of dialectical argumentation. (shrink)

The concept of legal power is important in the law since, with regard to actions having legal effect, the “exercise of legal power” delimits those actions for which manifestation of intention to achieve a legal effect is essential for the effect to ensue. The paper proposes a definition that captures this feature of legal power and marks it off from “direct effect,” as well as from permissibility and practical ability to achieve the legal effect. This analysis of power is limited (...) to the “immediate” legal power of a physical person characterized by the power-holder achieving a legal result by the power-holder's own behaviour. It is argued that in the literature on power the concept of legal power is frequently construed in such a way that it becomes either too broad or too narrow. (shrink)

The notion of validity fulfils a crucial role in legal theory. In the emerging Web 3.0, Semantic Web languages, legal ontologies, and normative multi-agent systems are designed to cover new regulatory needs. Conceptual models for complex regulatory systems shape the characteristic features of rules, norms, and principles in different ways. This article outlines one of such multilayered governance models, designed for the CAPER platform, and offers a definition of Semantic Web Regulatory Models . It distinguishes between normative-SWRM and institutional-SWRM. It (...) also compares existing principles in privacy by design, linked open data , legal information institutes , and online dispute resolution . The article concludes by proposing the notion of Relational Law to summarize the ethical dimension of SWRM. Ethics are the only regulatory way to constitute a global space, out of the jurisdictional public domain set by national, international, or transnational law, and opposed to the private one. (shrink)

Information technology is so ubiquitous and AI’s progress so inspiring that also legal professionals experience its benefits and have high expectations. At the same time, the powers of AI have been rising so strongly that it is no longer obvious that AI applications (whether in the law or elsewhere) help promoting a good society; in fact they are sometimes harmful. Hence many argue that safeguards are needed for AI to be trustworthy, social, responsible, humane, ethical. In short: AI should be (...) good for us. But how to establish proper safeguards for AI? One strong answer readily available is: consider the problems and solutions studied in AI & Law. AI & Law has worked on the design of social, explainable, responsible AI aligned with human values for decades already, AI & Law addresses the hardest problems across the breadth of AI (in reasoning, knowledge, learning and language), and AI & Law inspires new solutions (argumentation, schemes and norms, rules and cases, interpretation). It is argued that the study of AI as Law supports the development of an AI that is good for us, making AI & Law more relevant than ever. (shrink)

The paper outlines ongoing research on logic-based tools for the analysis and representation of legal contracts, of the kind frequently encountered in large-scale engineering projects and complex, long-term trading agreements. We consider both contract formation and contract performance, in each case identifying the representational issues and the prospects for providing automated support tools.

This study realizes belief/reliability change of a judge in a legal judgment by dynamic epistemic logic. A key feature of DEL is that possibilities in an agent’s belief can be represented by a Kripke model. This study addresses two difficulties in applying DEL to a legal case. First, since there are several methods for constructing a Kripke model, our question is how we can construct the model from a legal case. Second, since this study employs several dynamic operators, our question (...) is how we can decide which operators are to be applied for belief/reliability change of a judge. In order to solve these difficulties, we have implemented a computer system which provides two functions. First, the system can generate a Kripke model from a legal case. Second, the system provides an inconsistency solving algorithm which can automatically perform several operations in order to reduce the effort needed to decide which operators are to be applied. By our implementation, the above questions can be adequately solved. With our analysis method, six legal cases are analyzed to demonstrate our implementation. (shrink)

Much legal research focuses on understanding how judicial decision-makers exercise their discretion. In this paper we examine the notion of legal or judicial discretion, and weaker and stronger forms of discretion. At all times our goal is to build cognitive models of the exercise of discretion, with a view to building computer software to model and primarily support decision-making. We observe that discretionary decision-making can best be modeled using three independent axes: bounded and unbounded, defined and undefined, and binary and (...) continuous. Examples of legal tasks are given from each of the eight ensuing octants and we conclude by saying what this model shows about current legal trends. We should stress that our taxonomy has been based on our observations of how discretionary legal decisions are made. No claim is made that our model is either complete (providing advice in every domain) or exact, but it does help knowledge engineers construct legal decision support systems in discretionary domains. (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 his last papers about deontic logic, von Wright sustained that there is no genuine logic of norms. We argue in this paper that this striking statement by the father of deontic logic should not be understood as a death sentence to the subject. Rather, it indicates a profound change in von Wright's understanding about the epistemic and ontological role of logic in the field of norms. Instead of a logical constructivism of deontic systems revealing a necessary structure of prescriptive (...) discourse, which marked his earlier efforts, he adopted the view that such systems should be seem as mere objects of comparison, i.e. as providing practical standards of rationality for normgiving activity. Within such view he proposed an interpretation of standard deontic logic in such a way to free deontic logicians from the philosophical difficulties related to the so-called Jørgensen's dilemma and deontic paradoxes. This effort, as we claim in the present paper, is an application of Wittgenstein's therapeutic method to dissolve philosophical difficulties caused by the use of logical tools to model relations between norms. (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.

This paper presents in outline Luigi Ferrajoli’s axiomatic and general theory of law, as developed in his lifelong work Principia Iuris . The first section focuses on the three main aspects of the theory: the methodological, the theoretical and the pragmatic, which respectively represent the theory’s syntax, semantics and its pragmatics. Ferrajoli identifies three deontic gaps of norms: firstly, the one between their validity and efficacy ; secondly, the one between their justice and validity ; and finally, and most importantly, (...) the one between validity and existence (i.e. normative force). The presence of such gaps is, according to Ferrajoli, the extraordinary innovation that entrenched constitutions have brought into modern legal systems, by establishing norms that are superior to statutes and case law. In this sense, all normative phenomena (except for the constitution itself) can be conceived both as norms and as facts. In the second section the role of juridical science is briefly discussed. (shrink)

This paper generalises classical revision theory of the AGM brand to sets of norms. This is achieved substituting input/output logic for classical logic and tracking the changes. Operations of derogation and amendment—analogues of contraction and revision—are defined and characterised, and the precise relationship between contraction and derogation, on the one hand, and derogation and amendment on the other, is established. It is argued that the notion of derogation, in particular, is a very important analytical tool, and that even core deontic (...) concepts such as that of permission resists a satisfactory analysis without it. By way of illustration the last section of the paper analyses the much debated concept of positive permission, of which there turns out to be more than one kind. (shrink)

Computational approaches to the law have frequently been characterized as being formalistic implementations of the syllogistic model of legal cognition: using insufficient or contradictory data, making analogies, learning through examples and experiences, applying vague and imprecise standards. We argue that, on the contrary, studies on neural networks and fuzzy reasoning show how AI & law research can go beyond syllogism, and, in doing that, can provide substantial contributions to the law.

This paper aims at providing an account of juridical acts that forms a suitable starting point for the creation of computational systems that deal with juridical acts. The paper is divided into two parts. Because juridical acts will be analyzed as intentional changes in the world of law, the ‘furniture’ of this world, that consists broadly speaking of entities, facts and rules, plays a central role in the analysis. This first part of the paper deals with this furniture and its (...) philosophical underpinnings, and at the same time introduces most of the logical apparatus that will be used to deal with it. The focus in the first part is on static and dynamic legal rules and their interplay in constituting the world of law. (shrink)

Considerable attention has been given to the accessibility of legal documents, such as legislation and case law, both in legal information retrieval (query formulation, search algorithms), in legal information dissemination practice (numerous examples of on-line access to formal sources of law), and in legal knowledge-based systems (by translating the contents of those documents to ready-to-use rule and case-based systems). However, within AI & law, it has hardly ever been tried to make the contents of sources of law, and the relations (...) among them, more accessible to those without a legal education. This article presents a theory about translating sources of law into information accessible to persons without a legal education. It illustrates the theory by providing two elaborated examples of such translation ventures. In the first example, formal sources of law in the domain of exchanging police information are translated into rules of thumb useful for policemen. In the second example, the goal of providing non-legal professionals with insight into legislative procedures is translated into a framework for making available sources of law through an integrated legislative calendar. Although the theory itself does not support automating the several stages described, in this article some hints are given as to what such automation would have to look like. (shrink)