This article described three heuristics that are employed in making judgements under uncertainty: representativeness, which is usually employed when people are asked to judge the probability that an object or event A belongs to class or process B; availability of instances or scenarios, which is often employed when people are asked to assess the frequency of a class or the plausibility of a particular development; and adjustment from an anchor, which is usually employed in numerical prediction when a relevant value (...) is available. These heuristics are highly economical and usually effective, but they lead to systematic and predictable errors. A better understanding of these heuristics and of the biases to which they lead could improve judgements and decisions in situations of uncertainty. (shrink)

A new pragmatic approach, based on the latest developments in argumentation theory, analyzing appeal to expert opinion as a form of argument. Reliance on authority has always been a common recourse in argumentation, perhaps never more so than today in our highly technological society when knowledge has become so specialized—as manifested, for instance, in the frequent appearance of "expert witnesses" in courtrooms. When is an appeal to the opinion of an expert a reasonable type of argument to make, and when (...) does it become a fallacy? This book provides a method for the evaluation of these appeals in everyday argumentation. Specialized domains of knowledge such as science, medicine, law, and government policy have gradually taken over as the basis on which many of our rational decisions are made daily. Consequently, appeal to expert opinion in these areas has become a powerful type of argument. Challenging an argument based on expert scientific opinion, for example, has become as difficult as it once was to question religious authority. Walton stresses that even in cases where expert opinion is divided, the effect of it can still be so powerful that it overwhelms an individual's ability to make a decision based on personal deliberation of what is right or wrong in a given situation. The book identifies the requirements that make an appeal to expert opinion a reasonable or unreasonable argument. Walton's new pragmatic approach analyzes that appeal as a distinctive form of argument, with an accompanying set of appropriate critical questions matching the form. Throughout the book, a historical survey of the key developments in the evolution of the argument from authority, dating from the time of the ancients, is given, and new light is shed on current problems of "junk science" and battles between experts in legal argumentation. (shrink)

David N. Perkins has studied everyday reasoning by an experimental-critical approach involving taped interviews during which subjects reflect on controversial issues and articulate their reasoning on both sides. The present author has studied scientific reasoning in natural language by an historical-textual approach involving the reconstruction and evaluation of the arguments in Galileo's Two Chief World Systems. They have, independently, reached the strikingly similar substantive conclusion that the most common flaw of informal reasoning is the failure to consider lines of argument (...) supporting conclusions contrary to the one in fact reached. This article describes, compares, and contrasts their respective approaches, results, and theoretical frameworks. (shrink)

In Fallacies and Judgments of Reasonableness, Frans H. van Eemeren, Bart Garssen and Bert Meuffels report on their systematic empirical research of the conventional validity of the pragma-dialectical discussion rules. The experimental studies they carried out during more than ten years start from the pragma-dialectical theory of argumentation developed at the University of Amsterdam, their home university. In these studies they test methodically the intersubjective acceptability of the rules for critical discussion proposed in this theory by confronting ordinary arguers who (...) have not received any special education in argumentation and fallacies with discussion fragments containing both fallacious and non-fallacious argumentative moves. The research covers a wide range of informal fallacies. In this way, the authors create a basis for comparing the theoretical reasonableness conception of pragma-dialectics with the norms for judging argumentative moves prevailing in argumentative practice. Fallacies and Judgments of Reasonableness provides a unique insight into the relationship between theoretical and practical conceptions of reasonableness, supported by extensive empirical material gained by means of sophisticated experimental research. (shrink)

lt is now commonplace in fallacy inquiry for many of the traditional informal fallacies to be viewed as reasonable or nonfallacious modes of argument. Central to this evaluative shift has been the attempt to examine traditional fallacies within their wider contexts of use. However, this pragmatic turn in fallacy evaluation is still in its infancy. The true potential of a contextual approach in the evaluation of the fallacies is yet to be explored. I examine how, in the context of scientific (...) inquiry, certain traditional fallacies function by conferring epistemic gains upon inquiry. Specifically, I argue that these fallacies facilitate the progression of inquiry, particularly in the initial stages ofinquiry when the epistemic context is one of uncertainty. The conception of these fallacies that emerges is that of heuristics of reasoning in contexts of epistemic uncertainty. (shrink)

It is a feature of scientific inquiry that it proceeds alongside a multitude of non-scientific interests. This statement is as true of the scientific inquiries of previous centuries, many of which brought scientists into conflict with institutionalised religious thinking, as it is true of the scientific inquiries of today, which are conducted increasingly within commercial and political contexts. However, while the fact of the coexistence of scientific and non-scientific interests has changed little over time, what has changed with time is (...) the effect of this coexistence on scientific inquiry itself. While scientists may no longer construct their theories with various religious dictates in mind, growing commercial and political interests in science have served to distort the interpretation of science. Using the U.K.’s recent crisis with bovine spongiform encephalopathy (BSE) as my context, I examine two ways in which this distortion has occurred – the interpretation of the science of BSE by politicians and by commercial parties for the purposes of justifying policy decisions and informing the public of risk, respectively. Fallacious reasoning, I contend, is the manifestation of this distortion in these contexts. In demonstration of this claim, I examine how politicians and commercial parties alike have employed two fallacies in their assessments of the science of BSE. These fallacies extend in novel ways the set of so-called traditional informal fallacies. The interpretation of science, I conclude, is a rich context in which to conduct a study of fallacious reasoning; moreover, such a study can contribute in significant ways, I argue, to the public understanding of science. (shrink)