This paper takes an argumentation approach to find the place of trust in a method for evaluating arguments from expert opinion. The method uses the argumentation scheme for argument from expert opinion along with its matching set of critical questions. It shows how to use this scheme in three formal computational argumentation models that provide tools to analyse and evaluate instances of argument from expert opinion. The paper uses several examples to illustrate the use of these tools. A conclusion of (...) the paper is that from an argumentation point of view, it is better to critically question arguments from expert opinion than to accept or reject them based solely on trust. (shrink)

A Bibliography of Douglas Walton’s Published Works, 1971-20.

I explore how empathetic visual argument may be the mode best suited for eliciting appropriate force to the reasons given by arguers who face systematic identity prejudices. In the verbal mode, this force is often skewed through epistemic injustice, argumentative injustice, and discursive injustice. Highlighting their reliance on the Aristotelian sense of enthymeme, I show how visual arguments are highly context specific. Using Ian Dove’s Visual Scheming and the theory of the Retort collective via case study, I demonstrate how the (...) visual mode can leave the appropriate force in the arguer’s control. (shrink)

In this paper, I contend that evidence-focused strategies of science communication may be complemented by possibly more effective rhetorical arguments in current public debates on vaccines. I analyse the case of direct science communication - that is, communication of evidence - and show that it is difficult to effectively communicate evidential standards of science in the presence of well-equipped anti-science movements. Instead, I argue that effective rhetorical tools involve ad hominem strategies, that is, arguments involving claims of expertise. I provide (...) a rationale, and sketch a methodology, for using ad hominem arguments in science communication. (shrink)

Douglas Walton has done extensive and valuable work on the concepts of presumption and practical reasoning. However, Walton’s attempt to model practical reasoning as presumptive is misguided. The notions of “inference” and of the burden of proof shifting back and forth between proponent and respondent are misleading and lead to counterintuitive consequences. Because the issue in practical reasoning is a proposal, not a proposition, there are, in the standard case, several perfectly good reasons on both sides simultaneously, which implies that (...) argument appraisal necessarily contains a subjective element—a fact argumentation theory needs to conceptualize. (shrink)

When the likelihood ratio approach is employed for evidential reasoning in law, it is often necessary to employ subjective probabilities, which are probabilities derived from the opinions and judgement of a human. At least three concerns arise from the use of subjective probabilities in legal applications. Firstly, human beliefs concerning probabilities can be vague, ambiguous and inaccurate. Secondly, the impact of this vagueness, ambiguity and inaccuracy on the outcome of a probabilistic analysis is not necessarily fully understood. Thirdly, the provenance (...) of subjective probabilities and the associated potential sources of vagueness, ambiguity and inaccuracy tend to be poorly understood, making it difficult for the outcome of probabilistic reasoning to be explained and validated, which is crucial in legal applications. The former two concerns have been addressed by a wide body of research in AI. The latter, however, has received little attention. This paper presents a novel approach to employ argumentation to reason about probability distributions in probabilistic models. It introduces a range of argumentation schemes and corresponding sets of critical questions for the construction and validation of argument models that define sets of probability distributions. By means of an extended example, the paper demonstrates how the approach, argumentation schemes and critical questions can be employed for the development of models and their validation in legal applications of the likelihood ratio approach to evidential reasoning. (shrink)

This paper shows how the critical questions matching an argumentation scheme can be mod-eled in the Carneades argumentation system as three kinds of premises. Ordinary premises hold only if they are supported by sufficient arguments. Assumptions hold, by default, until they have been questioned. With exceptions the negation holds, by default, until the exception has been supported by sufficient arguments. By “sufficient arguments”, we mean arguments sufficient to satisfy the applicable proof standard.

This paper considers how the terms ‘objection,’ ‘rebuttal,’ ‘attack,’ ‘refutation,’ ‘rebutting defeater’ and ‘undercutting defeater’ are used in writings on argumentation and artificial intelligence. The central focus is on the term ‘rebuttal.’ A provisional classification system is proposed that provides a normative structure within which the terms can be clarified, distinguished from each other, and more precisely defined.