 This is one of the reasons why Williamson argues that the semantics of the conditional is best treated as the truth function. The semantics is not something which every speaker knows, or is readily available to them. We do not learn to use “if” via the truth table. And we know that no semantic theory of the conditional is obviously correct! The probabilities generated by the semantics are typically higher, and never lower than the probabilities generated by our basic suppositional procedure for assessing conditionals. Nevertheless, he argues, the truth-functional semantics does the best job of rationalizing our overall practice. 