There are obvious benefits to be gained from the study of logic: heightened ability to express ideas clearly and concisely, increased skill in defining one's terms, enlarged capacity to formulate arguments rigorously and to analyze them critically. But the greatest benefit, in my judgment, is the recognition that reason can be applied in every aspect of human affairs.

In some recent cases in Anglo-American law juries ruled contrary to an expert's testimony even though that testimony was never challenged, contradicted or questioned in the trial. These cases are shown to raise some theoretical questions about formal dialogue systems in computational dialectical systems for legal argumentation of the kind recently surveyed by Bench-Capon (1997) and Hage (2000) in this journal. In such systems, there is a burden of proof, meaning that if the respondent questions an argument, the proponent is (...) obliged to offer some support for it give it up. But what should happen in a formal system of dialogue if the proponent puts forward an argument and the respondent fails to critically question it, and simply moves on to another issue? Is this some kind of fault that should have implications? Should it be taken to imply that, by default, the respondent has conceded the argument? What, if anything, should be the outcome of such a failure to question in a formal dialogue system of argumentation? These questions are considered by examining some legal cases of expert opinion testimony in relation rules for formal dialectical argumentation systems. (shrink)

This paper presents an analysis of the concept of burden of proof in argument. Relationship of burden of proof to three traditional informal fallacies is considered: (i) argumentum ad hominem, (ii) petitio principii, and (iii) argumentum ad ignorantiam. Other topics discussed include persuasive dialoque, pragmatic reasoning, legal burden of proof, plausible reasoning in regulated disputes, rules of dialogue, and the value of reasoned dialogue.

The article discusses burden of proof rules in social criticism. By social criticism I mean an argumentative situation in which an opponent publicly argues against certain social practices; the examples I consider are discrimination on the basis of species and discrimination on the basis of one's nationality. I argue that burden of proof rules assumed by those who defend discrimination are somewhat dubious. In social criticism, there are no shared values which would uncontroversially determine what is the reasonable presumption and (...) who has the burden of proof, nor are there formal rules which would end the debate and determine the winner at a specific point. (shrink)

tational background of dialectic: the structure of formal disputation. Formal disputation Perhaps the clearest, and surely historically the most prominent, ...

Pascal‘s wager is expounded as a paradigm case of a practical,decision-theoretical argument for acting as if a proposition is true when wehave no theoretical reasons to accept or reject it (1.1.–1.2.). Thoughthe paradigm is fallacious in various respects there are valid and adequatearguments for acting as if certain propositions are true: that theoreticalentities exist, that there are material perceptual objects, that the worldis uniform across time (1.3). After this analysis of examples the author‘sgeneral approach for developing criteria for the validity (...) and adequacy oftypes of argument (2.1.) is applied: Having discussed some problems(2.2.–2.3.), a general epistemic principle for such ’pascal arguments‘is developed, which characterizes their premisses and, if introduced as anadditional premiss, can make them deductively valid (2.4). (shrink)

Bayesian reasoning has been applied formally to statistical inference, machine learning and analysing scientific method. Here I apply it informally to more common forms of inference, namely natural language arguments. I analyse a variety of traditional fallacies, deductive, inductive and causal, and find more merit in them than is generally acknowledged. Bayesian principles provide a framework for understanding ordinary arguments which is well worth developing.

This paper joins the voices warning against hasty transference of legal concepts of presumption to other kinds of argumentation, especially to deliberation about future acts and policies. Comparison of the pragmatics which respectively constitute the illocutionary acts of accusing and proposing reveals important differences in the ways presumptions prompt accusers and proposers to undertake probative responsibilities and, also, points to corresponding differences in their probative duties. This comparison has theoretically important implication regarding the norms governing persuasive argumentation. The paper is (...) based on a broadly Gricean account of speech acts. (shrink)

We examine in detail three classic reasoning fallacies, that is, supposedly ``incorrect'' forms of argument. These are the so-called argumentam ad ignorantiam, the circular argument or petitio principii, and the slippery slope argument. In each case, the argument type is shown to match structurally arguments which are widely accepted. This suggests that it is not the form of the arguments as such that is problematic but rather something about the content of those examples with which they are typically justified. This (...) leads to a Bayesian reanalysis of these classic argument forms and a reformulation of the conditions under which they do or do not constitute legitimate forms of argumentation. (shrink)

Public and professional debates have come to rely heavily on a special type of reasoning: the argument-from-ignorance, in which conclusions depend on the _lack_ of compelling information. "I win my argument," says the skillful advocate, "unless you can prove that I am wrong." This extraordinary gambit has been largely ignored in modern rhetorical and philosophical studies. Yet its broad force can be demonstrated by analogy with the modern legal system, where courts have long manipulated burdens of proof with skill and (...) subtlety. This legal, philosophical, and rhetorical study by Richard H. Gaskins provides the first systematic treatment of arguments-from-ignorance across a wide range of modern discourse—from constitutional law, scientific inquiry, and moral philosophy to organizational behavior, computer operation, and personal interaction. Gaskins reviews the historic shifts in constitutional proof burdens that have shaped public debate on fundamental rights and, by analogy, on the fundamental status of intellectual and cultural authority. He shows how similar shifts have dominated polemical battles between scientific and ethical modes of authority, affecting both academic and popular discussion. Finally, he discovers the philosophical roots of default reasoning strategies in the arguments of Kant and nineteenth-century Kantian schools. Concluding that shifting proof burdens are inescapable in a world of scientific and moral uncertainty, Gaskins emphasizes the common strategic ground shared by dogmatic and skeptical reasoning. Using Hegelian strategies, he describes a more pluralistic temper that can move critical thinking beyond polemics and strengthen our capacities for common discourse. (shrink)

_Arguments from Ignorance _explores the situations in which the argument from ignorance functions as a respectable form of reasoning and those in which it is indeed fallacious. Douglas Walton draws on everyday conversations on all kinds of practical matters in which the _argumentum ad ignorantiam _is used quite appropriately to infer conclusions. He also discusses the inappropriate use of this kind of argument, referring to various major case studies, including the Salem witchcraft trials, the McCarthy hearings, and the Alger Hiss (...) case. This book makes an original contribution in the areas of argumentation theory and informal logic, contending that, despite its traditional classification as a fallacy, the argument from ignorance is a genuine, very common, and legitimate type of argumentation with an identifiable structure. But the book is also interdisciplinary in scope, explaining many widely interesting and controversial subjects in artificial intelligence, medical education, philosophy of science, and philosophy of law in a clear way that makes it accessible to a broad range of readers. (shrink)

In this paper I explore Ralph Johnson's proposal that in addition to premises and conclusion every argument should have a dialectical tier in which the arguer addresses objections to the argument, and considers alternative positions. After exploring several reasons for thinking that Johnson's proposal is a good one, I then raise a number of objections against it and move ahead to respond to those objections, which I do by distinguishing making out a case for a conclusion from offering an argument (...) for it, and distinguishing supplementary arguments from one's main argument. I contend that it is not realistic to see arguers as having an obligation to respond to all objections and to address all alternative positions; we must somehow discriminate those which need and merit a reply from those which do not. (shrink)

Bayesian reasoning has been applied formally to statistical inference, machine learning and analysing scientific method. Here I apply it informally to more common forms of inference, namely natural language arguments. I analyse a variety of traditional fallacies, deductive, inductive and causal, and find more merit in them than is generally acknowledged. Bayesian principles provide a framework for understanding ordinary arguments which is well worth developing.