Abstract

In one of his papers, Moti Mizrahi argues that arguments from an expert opinion are weak arguments. His thesis may seem controversial due to the consensus on this topic in the field of informal logic. I argue that its controversy is framework-dependent, and if translated into a different framework, it appears to be a correct, however trivial, claim. I will use a framework based on Douglas Walton’s argumentation scheme theory and his conception of examination dialogue to demonstrate that it is so. It appears that Mizrahi’s idiosyncratic framework provides an excessively restrictive conception of an argument from expert opinion than Walton’s scheme does. There is no quarrel between both frameworks, as they yield analogous, almost identical, outcomes of argument evaluation. The actual and crucial disagreement is on the topic of argument classification. Mizrahi’s conception of arguments from an expert opinion imposes exact conditions that such argument must fulfil: an expert’s opinion o truth-value must be unknown; o must be unsupported by any evidence; an expert’s peers neither accept o nor reject it. These exclude, by definition, every possible strong, in Walton’s terms, variant of such an argument. Therefore, if rephrased with the notions of the examination dialogue framework, Mizrahi’s thesis sounds as follows: weak arguments from expert opinion are weak arguments.