 The modern study of logic is commonly dated to 1847, with the appearance of Boole’s Mathematical Analysis of Logic. This work established that Aristotle’s syllogistic logic can be translated into an algebraic calculus, whose symbols Boole interpreted as referring either to classes or to propositions. His system encompasses what is today called sentential (or Boolean) logic, but it is also capable of expressing rudimentary quantifications. For instance, the proposition “All Xs are Ys” is represented in his system by the equation \(xy = x\), with the multiplication being thought of either as an intersection of sets, or as logical conjunction. “Some Xs are Ys” is more difficult, and its expression more artificial. Boole introduces a (tacitly: non-empty) set V containing the items common to X and Y; the proposition is then written \(xy = V\) (1847: 21). Boole’s system, in modern terms, can be viewed as a fragment of monadic first-order logic. It is first-order because its notational resources cannot express a quantification that ranges over predicates. It is monadic because it has no notation for n-ary relations. And it is a fragment because it cannot express nested quantifications (“for every girl, there exists a boy who loves her”). But these are our categories: not Boole’s. His logical system has no symbols corresponding to the quantifiers; so even to call it a restricted system of quantificational logic is anachronistic.