 Medieval LOT theorists used syllogistic and propositional logic to analyze the semantics of Mentalese (King 2005; Normore 1990). Contemporary proponents instead use the predicate calculus, which was discovered by Frege (1879 [1967]) and whose semantics was first systematically articulated by Tarski (1933 [1983]). The view is that Mentalese contains primitive words—including predicates, singular terms, and logical connectives—and that these words combine to form complex sentences governed by something like the semantics of the predicate calculus.