Abstract

Timothy Williamson contends that our primary cognitive heuristic for prospectively assessing conditionals, i.e., the suppositional procedure, is provably inconsistent. Our diagnosis is that stipulations about the nature of suppositional rejection are the likely source of these results. We show that on at least one alternative, and quite natural, understanding of the suppositional attitudes, the inconsistency results are blocked. The upshot is an increase in the reliability of our suppositional heuristics across a wider range of contexts. One interesting consequence of the increased reliability is a proportional decrease in the plausibility of an error-theory that Williamson employs against widespread intuitions about the truth values of counterpossible conditionals.