Accounts of arguments from expert opinion take it for granted that expert judgments count as (defeasible) evidence for propositions, and so an argument that proceeds from premises about what an expert judges to a conclusion that the expert is probably right is a strong argument. In Mizrahi (2013), I consider a potential justification for this assumption, namely, that expert judgments are significantly more likely to be true than novice judgments, and find it wanting because of empirical evidence suggesting that expert (...) judgments under uncertainty are not significantly more likely to be true than novice judgments or even chance. In this paper, I consider another potential justification for this assumption, namely, that expert judgments are not influenced by the cognitive biases novice judgments are influenced by, and find it wanting, too, because of empirical evidence suggesting that experts are vulnerable to pretty much the same cognitive biases that novices are vulnerable to. If this is correct, then the basic assumption at the core of accounts of arguments from expert opinion, namely, that expert judgments count as (defeasible) evidence for propositions, remains unjustified. (shrink)

ABSTRACTIn order to properly understand how expert disagreement should be dealt with, it is essential to grasp how expert opinion is used in the reasoning process by which humans reach conclusions and make decisions. This paper utilises the tools of argumentation theory, specifically Douglas Walton’s argument schemes, and variations upon them, in order to examine how patterns of reasoning are affected by the presence of conflicting testimony. This study suggests that although it may be supplemented with the construction of epistemic (...) hierarchies, the scheme of reasoning for the appeal to expert opinion provides no mechanism for establishing a preference for one expert statement over another, making it impossible to reach any rational conclusion as to the likely truth of the matter. Further, it is also argued that other schemes for presumptive argumentation are either unhelpful in themselves or lead to unwanted consequences. (shrink)