In this paper, we introduce the subject of the special issue Trends in Argumentation Logic. Here we mainly describe two approaches to argumentation logic with explicating monotonic and non-monotonic, or defeasible, reasoning and explain the role of artificial intelligence in applying argumentation logic. Then we give a short overview of the papers contributed to the special issue.

John Pollock (1940?2009) was an influential American philosopher who made important contributions to various fields, including epistemology and cognitive science. In the last 25 years of his life, he also contributed to the computational study of defeasible reasoning and practical cognition in artificial intelligence. He developed one of the first formal systems for argumentation-based inference and he put many issues on the research agenda that are still relevant for the argumentation community today. This paper presents an appreciation of Pollock's work (...) on defeasible reasoning and its relevance for the computational study of argument. In our opinion, Pollock deserves to be remembered as one of the founding fathers of the field of computational argument, while, moreover, his work contains important lessons for current research in this field, reminding us of the richness of its object of study. (shrink)

Belief formation and justification of belief is the subject of epistemology, philosophy of mind, and philosophy of action. In this article we are mostly interested in the application of analytic techniques for the explication of belief justification under uncertainty. We need to explicate this phenomenon in order to answer, at least in part, the question of what are the features of reasoning made in conditions that cause doubts, how people make decisions in such conditions. Arguments used for the justification of (...) such decisions have the status of plausible arguments. The crucial issues related to the analysis and evaluation of plausible arguments are of the acceptability of the premises and the transmission of their acceptability to the conclusion. In this article, we have focused on the transition from the premises to the conclusions of plausible arguments, on the transmission of justification of premises to the conclusions. To establish the peculiarities of such a transmission an outline of the semantics for such arguments is proposed. Its key component is the measures of the plausibility of the premises and rules of inference. A plausible argument itself does not provide the ultimate reason for accepting its conclusion. The justification of the conclusion also depends on other arguments that support or defeat it. So to establish the degree of justification of the conclusion we need to attribute the weights to the premises and rules of inference. We hope that this study provides at least a preliminary answer to the question of how the failure of the transmission of justification in plausible arguments differs from the failure of transmission in deductive arguments. (shrink)

Conciliatory views of disagreement say, roughly, that it’s rational for you to become less confident in your take on an issue in case you find out that an epistemic peer’s take on it is the opposite. Their intuitive appeal notwithstanding, there are well-known worries about the behavior of conciliatory views in scenarios involving higher-order disagreements, which include disagreements over these views themselves and disagreements over the peer status of alleged epistemic peers. This paper does two things. First, it explains how (...) the core idea behind conciliatory views can be expressed in a defeasible logic framework. The result is a formal model that’s particularly useful for thinking about the behavior of conciliatory views in cases involving higher-order disagreements. And second, the paper uses this model to resolve three paradoxes associated with disagreements over epistemic peerhood. (shrink)

According to conciliatory views on the significance of disagreement, it’s rational for you to become less confident in your take on an issue in case your epistemic peer’s take on it is different. These views are intuitively appealing, but they also face a powerful objection: in scenarios that involve disagreements over their own correctness, conciliatory views appear to self-defeat and, thereby, issue inconsistent recommendations. This paper provides a response to this objection. Drawing on the work from defeasible logics paradigm and (...) abstract argumentation, it develops a formal model of conciliatory reasoning and explores its behavior in the troubling scenarios. The model suggests that the recommendations that conciliatory views issue in such scenarios are perfectly reasonable—even if outwardly they may look odd. (shrink)

En este escrito se presentan las bases de una estrategia pragmática, contextualista e inferencialista para articular una teoría que dé cuenta de los grados de justificación de nuestras aserciones. Se arguye que hay contextos de emisión de aserciones configurados con ciertos criterios inferenciales, los cuales responden a propósitos prácticos o teóricos, y conforman, en consecuencia, diferentes estándares de justificación en esos contextos. Finalmente, a partir de una caracterización de tipos de proposiciones, inferencias, compromisos asertivos y esquemas de justificación, se muestra (...) cómo determinar el grado de justificación alto, medio o bajo de una aserción con respecto a un contexto de emisión de aserciones dado. (shrink)

Scott Sturgeon has recently challenged Pollock’s account of undercutting defeaters. The challenge involves three primary contentions: the account is both too strong and too weak, undercutting defeaters exercise their power to defeat only in conjunction with higher-order beliefs about the basis of the lower-order beliefs whose justification they target, and since rebutting defeaters exercise their power to defeat in isolation, rebutting and undercutting defeaters work in fundamentally different ways. My goal is to reject each of these contentions. I maintain that (...) Sturgeon fails to show that Pollock’s account of undercutting defeaters is either too strong or too weak, his own account of how undercutting defeaters exercise their power to defeat is both too strong and too weak, and his claim that rebutting and undercutting defeaters work in fundamentally different ways is mistaken. (shrink)

An approach to argument macrostructure -- The dialectical nature of argument -- Toulmin's problematic notion of warrant -- The linked-convergent distinction, a first approximation -- Argument structure and disciplinary perspective : the linked-convergent versus multiple-co-ordinatively compound distinctions -- The linked-convergent distinction, refining the criterion -- Argument structure and enthymemes -- From analysis to evaluation.

This paper overviews some recent work on the semantics and pragmatics of arguments.

The concept of conductive argument weight was developed by Carl Wellman and later by Trudy Govier. This concept has received renewed attention recently from another informal logician, Robert C. Pinto. Argument weight has also been addressed in recent years by theorists in AI & Law. I argue from a non-technical perspective that some aspects of AI & Law’s approach to argument weight can be usefully applied to the issues addressed by Pinto. I also relate some of these issues to the (...) work of argument theorist Harald Wohlrapp. (shrink)

Understanding the language of rejections and objections is an important part of the analysis and practice of argument. In order to strengthen this understanding, we might turn to diagramming, as it has been shown to have the virtue of improving critical thinking skills. This paper discusses what reliable meaning can be taken from words and phrases related to rejections and objections, and then how to diagram them.