The purpose of this paper is to analyze the structure and the defeasibility conditions of argument from analogy, addressing the issues of determining the nature of the comparison underlying the analogy and the types of inferences justifying the conclusion. In the dialectical tradition, different forms of similarity were distinguished and related to the possible inferences that can be drawn from them. The kinds of similarity can be divided into four categories, depending on whether they represent fundamental semantic features of the (...) terms of the comparison or non-semantic ones, indicating possible characteristics of the referents. Such distinct types of similarity characterize different kinds of analogical arguments, all based on a similar general structure, in which a common genus is abstracted. Depending on the nature of the abstracted common feature, different rules of inference will apply, guaranteeing the attribution of the analogical predicate to the genus and to the primary subject. This analysis of similarity and the relationship thereof with the rules of inference allows a deeper investigation of the defeasibility conditions. (shrink)

Following a linguistic-descriptivist approach, Marianne Doury has studied debates about “parasciences”, discovering that “parascientists” frequently argue by “appeal to Galileo” ; opponents object by criticizing the analogy, charging fallacy, and appealing to counter-examples. I argue that Galilean appeals are much more widely used, by creationists, global-warming skeptics, advocates of “settled science”, great scientists, and great philosophers. Moreover, several subtypes should be distinguished; critiques questioning the analogy are proper; fallacy charges are problematic; and appeals to counter-examples are really indirect critiques of (...) the analogy. (shrink)