 The first attempt to construct a theory of compounds of conditionals, compatible with Supp’s thesis, is due to Bruno de Finetti (1936), who, shortly after Ramsey, independently developed a theory of probability as degree of belief, and like Ramsey, saw that conditional probability seemed a good measure of one’s degree of belief in a conditional. To deal with compounds of conditionals, he proposed a three-valued semantics for the conditional—true, false, undefined. “If \(A, B\)” is true if \(A \amp B\), false if \(A \amp{\sim}B\), and lacks a truth value—is undefined—if \({\sim}A\). He called these semantic entities “conditional events” or “tri-events”. The probability of a conditional is not the probability of its truth (which is just the probability of \(A \amp B)\), but the probability of its truth given that it is either true or false, which is just the conditional probability of \(B\) given \(A\). Then de Finetti gave truth tables, which accommodate compounds of conditionals. A conjunction is true iff both conjuncts are true, false iff at least one conjunct is false, otherwise undefined. A disjunction is true iff at least one disjunct is true, false if both disjuncts are false, otherwise undefined. Negation takes true to false, false to true, undefined to undefined. A conditional with a false or undefined antecedent is undefined. And the probability of a compound is also the probability that it is true, given that it is either true or false. For work in this tradition see Milne (1997). See also Belnap (1970) and McDermott (1996).