 that is, the propensity for \(G\), given \(F \amp H\), differs from the propensity for \(G\), given \(F \amp \neg H\), where the presence or absence of \(H\) affects the single-case causal tendency for \(G\). The universal generalization of sentential functions like these thus produces lawlike sentences, while their instantiation to individual constants or to ambiguous names produces (what are known as) nomological conditionals (Fetzer 1981: 49–54). The introduction of the probabilistic causal calculus \(C\), moreover, responds to Salmon’s concerns by providing a formalization within intensional logic that resolves them (Fetzer &amp; Nute 1979, 1980). Paul Humphreys (1985, 1989) has argued that “propensities cannot be probabilities” because their causal directedness precludes satisfying symmetry conditions requiring probabilities from effects to causes as well as from causes to effects (on the plausible assumption that there are no propensities for effects to bring about their causes). A more linguistically precise characterization would be that propensities cannot be ‘standard probabilities’, which has no effect on their role in explanatory contexts.