The Adams family

According to Adams’s Thesis, the acceptability of an indicative conditional sentence goes by the conditional probability of its consequent given its antecedent. We test, for the first time, whether this thesis is descriptively correct and show that it is not; in particular, we show that it yields the wrong predictions for people’s judgments of the acceptability of important subclasses of the class of inferential conditionals. Experimental results are presented that reveal an interaction effect between, on the one hand, the type of inferential connection between a conditional’s antecedent and its consequent and, on the other, the judged acceptability of the conditional in relation to the conditional probability of its consequent given its antecedent. Specifically, these results suggest a family of theses, each pertaining to a different type of conditional, about how conditionals relate to the relevant conditional probabilities.