Fabrizio Macagno

Argument diagramming in logic, law and artificial intelligence

In this paper, we present a survey of the development of the technique of argument diagramming covering not only the fields in which it originated — informal logic, argumentation theory, evidence law and legal reasoning — but also more recent work in applying and developing it in computer science and artificial intelligence (AI). Beginning with a simple example of an everyday argument, we present an analysis of it visualized as an argument diagram constructed using a software tool. In the context of a brief history of the development of diagramming, it is then shown how argument diagrams have been used to analyse and work with argumentation in law, philosophy and AI.

Argument from Analogy in Law, the Classical Tradition, and Recent Theories

Argument from analogy is a common and formidable form of reasoning in law and in everyday conversation. Although there is substantial literature on the subject, according to a recent survey (Juthe 2005) there is little fundamental agreement on what form the argument should take, or on how it should be evaluated. Th e lack of conformity, no doubt, stems from the complexity and multiplicity of forms taken by arguments that fall under the umbrella of analogical reasoning in argumentation, dialectical studies, and law. Modeling arguments with argumentation schemes has proven useful in attempts to refine the analyst’s understanding of not only the logical structures that shape the backbone of the argument itself, but also the logical underpinning of strategies for evaluating it, strategies based on the semantic categories of genus and relevance. By clarifying the distinction between argument from example and argument from analogy, it is possible to advance a useful proposal for the treatment of argument from analogy in law.

Implicatures as Forms of Argument

In this paper, we use concepts, structure and tools from argumentation theory to show how conversational implicatures are triggered by conflicts of presumptions. Presumptive implicatures are shown to be based on defeasible forms of inference used in conditions of lack of knowledge, including analogical reasoning, inference to the best explanation, practical reasoning, appeal to pity, and argument from cause. Such inferences are modelled as communicative strategies used to fill knowledge gaps by shifting the burden of proof to provide the missing contrary evidence to the other party in a dialogue. Through a series of illustrative examples, we show how such principles of inference are based on common knowledge about the ordinary course of events shared by participants in a structured dialogue setting in which they take turns putting forward and responding to speech acts.

Developing Argumentation Strategies in Electronic Dialogs: Is Modeling Effective?

The study presented here examines how interacting with a more capable interlocutor influences use of argumentation strategies in electronic discourse. To address this question, 54 young adolescents participating in an intervention centered on electronic peer dialogs were randomly assigned to either an experimental or control condition. In both conditions, pairs who held the same position on a social issue engaged in a series of electronic dialogs with pairs who held an opposing position. In the experimental condition, in some dialogs, unbeknownst to them (because dialog took place electronically), the opponent was a more capable (“expert”) adult. Dialogs in the control condition were only with peers. Argumentation strategies of the experimental group who argued with the “expert” showed immediate strategy improvements in their subsequent peer dialogs, improvement absent in the control group (Cohens d = 1.12). In particular, the experimental group showed greater use of counterargument in general and advanced forms of counterargument (undermining) that challenges the deeper premises or reasoning on which an argument is based. Implications with respect to mechanisms of change in the development of argumentation skills are considered.

Argumentation schemes for statutory interpretation : a logical analysis

This paper shows how defeasible argumentation schemes can be used to represent the logical structure of the arguments used in statutory interpretation. In particular we shall address the eleven kinds of argument identified MacCormick and Summers [6] and the thirteen kinds of argument by Tarello [11]. We show that interpretative argumentation has a distinctive structure where the claim that a legal text ought or may be interpreted in a certain way can be supported or attacked by arguments, whose conflicts may have to be assessed according to further arguments. 1. Background: Arguments in Interpretation This paper aims at developing a fresh formal analysis of interpretive arguments, i.e., arguments meant to support a particular interpretation of a statutory test, and to justify its choice over competing interpretations. Our theoretical framework is based on three different dimensions: legal theories on interpretive arguments, argumentation theories for analysing such arguments, and argumentation logics for formalising them. In this section we will briefly present the legal doctrinal backgrounds for our formal analysis: MacCormick and Summers’s [6] analysis of interpretive arguments, Tarello’s [11] classification of interpretation canons, and Alexy and Dreier’s [1] analysis of criteria for solving interpretive conflicts. Generally speaking, the so-called interpretation canons — i.e., the different rules to be applied to interpreting statutes — that are employed in legal systems can be viewed as patterns for constructing arguments aimed at justifying certain interpretations, while attacking other interpretations. 1.1. The Proposal of MacCormick and Summers MacCormick and Summers [6, 464-5], summarising the outcomes of a vast study on statutory interpretation, involving scholars from many different legal systems, distinguish eleven types of arguments: 1. Arguments from ordinary meaning express the principle that if a statutory provision can be interpreted according to the meaning a native speaker of a given language would ascribe to it, it should be interpreted in this way, unless there is a reason for a different interpretation. 2. Arguments from technical meaning express the principle that if a statutory provision concerns a special activity that has a technical language, it ought to be interpreted in the appropriate technical sense, as opposed to its ordinary meaning. 3. Arguments from contextual harmonization express the principle that if the statutory provision belongs to a larger scheme in a statute or set of statutes, it should be interpreted in light of the whole statute it is part of, or in light of other statutes it is related to. 4. Arguments from precedent express the principle that if a statutory provision has a previous judicial interpretation, it should be interpreted in conformity with it. Where there is a hierarchy of courts, this principle needs to be applied in such a way to imply that the lower court must conform to the judgment of higher one. 5. Arguments from analogy express the principle that if a statutory provision is similar to provisions of other statutes, then it should be interpreted to preserve the similarity of meaning, even if this requires a departure from ordinary meaning. 6. Arguments from a legal concept express the principle that if the general legal concept has been previously recognized and doctrinally elaborated in law, it should be interpreted in such a way as to maintain a consistent use of the concept through the system as a whole. 7. Arguments from general principles express the principle that whenever general principles, including principles of law, are applicable to the statutory provision, one should favour the interpretation of that is most in conformity with these general legal principles. 8. Arguments from history express the principle that if the statute has come to be interpreted over a period of time in accord with the historically evolved understanding of a particular point, its application to a case should be interpreted in line with this historically evolved understanding. 9. Arguments from purpose express the principle that if a purpose can be ascribed to a statutory provision, or even to the whole statute, the provision should be interpreted as applied to a particular case in a way compatible with this purpose. 10. Arguments from substantive reasons express the principle that if there is some goal that can be considered to be fundamentally important to the legal order, and if the goal can be promoted by one rather than another interpretation of the statutory provision, then the provision should be interpreted in accord with the goal. 11. Arguments from intention express the principle that if a legislative intention concerning a statutory provision can be identified, the provision should be interpreted in line with that intention. 1.2. The Proposal of Tarello Some years before the comparative inquiry of MacCormick and Summers, a list of interpretive arguments was developed by Tarello [11, Ch. 8]. While being based mainly on the Italian tradition, this categorisation has had a broad influence also outside Italy, being adopted in particular by Perelman [9, 55-9]: 1. Arguments a contrario exclude interpretations according to which a legal statement explicitly saying “if A then B” is given the meaning “if A or C then B”, where C is any proposition not entailed by A. 2. Arguments a simili ad simile (or analogical) support interpretations according to which, a term in a legal statetment is extended to include entities that are not literally included in its scope, but present a relevant similarity with the entities literally included. 3. Arguments a fortiori support interpretations of a legal statement according to which a term in the statement, which apparently denotes a single class of subjects or acts, is extended to other subjects or acts, since these additional subjects or acts deserve to a larger extent the normative qualification linked to that term. 4. Arguments from completeness of the legal regulation exclude interpretations that create legal gaps. 5. Arguments from the coherence of the legal regulation exclude interpretations of different legal statements that make them conflicting. 6. Psychological arguments support interpretations driven by the actual intent of the authors of legal text (for instance, on the basis of the travaux préparatories). 7. Historical arguments support interpretations giving a legal statement the same meaning that was traditionally attributed to other statements governing the same matter. 8. Apagogical arguments exclude the interpretation of a normative statement that generates an absurdity. 9. Teleological arguments support the interpretation of a legal statement by attributing to it a rational purpose which is identified from the goals or interests that the law is supposed to promote; 10. Parsimony arguments exclude interpretations that are redundant under the assumption that the legislator does not make useless normative statements. 11. Authoritative arguments support interpretations already given by any authoritative judicial or doctrinal subject. 12. Naturalistic arguments support interpretations aligning a legal statement to human nature or the nature of the matter regulated by that statement. 13. Arguments from equity support (exclude) (un)fair or (un)just interpretations. 14. Arguments from general principles support (exclude) interpretations that are suggested by (incompatible with) general principles of the legal system. Tarello’s list complements MacCormick and Summers’ list, since the latter focuses on the kinds of input on which the interpretive argument is based (ordinary language, technical language, statutory context, precedent, etc.) while the first focuses on the reasoning steps by which the interpretive argument is constituted. 1.3. Priorities and Conflicts between Interpretive Arguments Interpretive argument can be in conflict one against another, leading to opposite conclusions. In fact, as MacCormick [5] observes, “there may be arguments of many types available, and each is capable of generating an interpretation of a given text at variance with that generated by some other possible argument”. To address such conflicts, we need to assume or argue that one of the conflicting arguments is stronger than its competitors. Some legal traditions provide indeed general criteria for addressing conflicts of arguments on the basis of their priorities. For instance, Alexy and Dreier [1, 95ff.] indicate various criteria according to which conflicts between interpretive arguments are adjudicated in German law: 1. In criminal law, arguments based on the wording of the text to be applied have strong priority. 2. In criminal law arguments based on ordinary meaning take priority over arguments which refer to technical terminology. 3. A strong priority for the wording obtains where the state wishes to interfere with individual rights of freedom. 4. A strong priority for the wording obtains for prescriptions on time limits. 5. A weak priority for arguments based on wording obtains in general. 6. Genetic arguments, based on the intention of the historical legislator, prevail over argument not based on authority (i.e., argument not based on the historical legislator’s intention, on precedent, or on dogmatic consensus), though not over linguistic arguments. 7. Rightness reasons based on the constitution or on superior sources have precedence over those who are not so grounded. 8. The idea that a scrutiny is required when limitations to individual liberties are at issue has led some to the idea, refused by others, that substantive arguments based on individual rights prevail over arguments based on collective goals. 1.4. A General Structure for Interpretive Arguments By analysing the different interpretive canons we can may identify a shared structure including the following elements: an expression E (word, phrase, sentence, etc.)

Analyzing the Pragmatic Structure of Dialogues

In this article, we describe the notion of dialogue move intended as the minimal unit for the analysis of dialogues. We propose an approach to discourse analysis based on the pragmatic idea that the joint dialogical intentions are also co-constructed through the individual moves and the higher-order communicative intentions that the interlocutors pursue. In this view, our goal is to bring to light the pragmatic structure of a dialogue as a complex net of dialogical goals (such as persuasion, deliberation, information-sharing, etc.), which represent the communicative purposes that the interlocutors intend to achieve through their utterances. Dialogue moves are shown to represent the necessary interpretive link between the general description of the dialogical context or type and the syntactical analysis of the sentences expressed by the individual utterances. In the concluding part of this article, we show how this method can be used and further developed for analyzing various types of real-life dialogues, outlining possible uses and lines of empirical research based thereon.

An argumentation framework for contested cases of statutory interpretation

This paper proposes an argumentation-based procedure for legal interpretation, by reinterpreting the traditional canons of textual interpretation in terms of argumentation schemes, which are then classified, formalized, and represented through argument visualization and evaluation tools. The problem of statutory interpretation is framed as one of weighing contested interpretations as pro and con arguments. The paper builds an interpretation procedure by formulating a set of argumentation schemes that can be used to comparatively evaluate the types of arguments used in cases of contested statutory interpretation in law. A simplified version of the Carneades Argumentation System is applied in a case analysis showing how the procedure works. A logical model for statutory interpretation is finally presented, covering pro-tanto and all-things-considered interpretive conclusions.

Manipulating Emotions: Value-Based Reasoning and Emotive Language

There are emotively powerful words that can modify our judgment, arouse our emotions, and influence our decisions. The purpose of this paper is to provide instruments for analyzing the structure of the reasoning underlying the inferences that they trigger, in order to investigate their reasonableness conditions and their persuasive effect. The analysis of the mechanism of persuasion triggered by such words involves the complex systematic relationship between values, decisions, and emotions, and the reasoning mechanisms that have been investigated under the label of “heuristics.” On the one hand, arguing using ethical words is shown to sometimes involve value-based practical reasoning grounded on evaluative classifications stemming from hierarchies of values and maxims of experience. On the other hand, ethical words provide representations bound to the interlocutors experiences and judgments, which trigger specific emotions yielding a particular reaction. This chain of judgments and reactions and the potential fallaciousness thereof can be inquired into by examining the relationship between the heuristic processes of reasoning and the more complex argumentative structure that the use of such words involves. The analysis of the 2013 Italian political campaign and the ad hominem arguments used by the political candidates shows the different strategies and counterstrategies for the manipulation of emotions.

The Fallaciousness of Threats: Character and Ad Baculum

Robert Kimball, in “What’s Wrong with ArgumentumAd Baculum?” (Argumentation, 2006) argues that dialogue-based models of rational argumentation do not satisfactorily account for what is objectionable about more malicious uses of threats encountered in some ad baculum arguments. We review the dialogue-based approach to argumentum ad baculum, and show how it can offer more than Kimball thinks for analyzing such threat arguments and ad baculum fallacies.

Common Knowledge in Legal Reasoning About Evidence

It is shown how tools of argument analysis currently being developed in artificial intelligence can be applied to legal judgments about evidence based on common knowledge. Chains of reasoning containing generalizations and implicit premises that express common knowledge are modeled using argument diagrams and argumentation schemes. A controversial thesis is argued for. It is the thesis that such premises can best be seen as commitments accepted by parties to a dispute, and thus tentatively accepted, subject to default should new evidence come in that would overturn them. Common knowledge, on this view, is not knowledge, strictly speaking, but a kind of provisional acceptance of a proposition based on its not being disputed, and its being generally accepted as true, but subject to exceptions.