The Role of Conditional Propositions
This chapter explains why the practice of using conditionals assessed by the primary (suppositional) and secondary (testimonial) heuristics is best understood on a material, truth-functional semantics. The aptness of the testimony-based heuristic supports a semantics on which the semantic contribution of ‘if’ is context-insensitive; the aptness of the supposition-based heuristic supports a semantics on which the probability of a conditional is not overestimated by being treated like the conditional probability, and compatibly with that underestimates it as little as possible. A formal result shows that in almost all cases these desiderata mandate the truth-functional interpretation. But that does not imply that the truth-functional interpretation will be transparent to speakers: it does not grant them epistemic access to the truth-conditional equivalence of ‘If A, C’ and ‘Not A or C’. This non-transparent ‘synonymy’ is compared to our understanding in cases of vagueness.