 Finally, it should be noted that although this subsection only discussed probabilistic semantics for classical propositional logic, there are also probabilistic semantics for a variety of other logics, such as intuitionistic propositional logic (van Fraassen 1981b, Morgan and Leblanc 1983), modal logics (Morgan 1982a, 1982b, 1983, Cross 1993), classical first-order logic (Leblanc 1979, 1984, van Fraassen 1981b), relevant logic (van Fraassen 1983) and nonmonotonic logic (Pearl 1991). All of these systems share a key feature: the logic’s semantics is probabilistic in nature, but probabilities are not explicitly represented in the object language; hence, they are much closer in nature to the propositional probability logics discussed here than to the systems presented in later sections.