Carl Hempel introduced what he called “Craig’s theorem” into the philosophy of science in a famous discussion of the “problem of theoretical terms.” Beginning with Hempel’s use of ‘Craig’s theorem,” I shall bring out some of the key differences between Hempel’s treatment of the “problem of theoretical terms” and Carnap’s in order to illuminate the peculiar function of Wissenschaftslogik in Carnap’s mature philosophy. Carnap’s treatment, in particular, is fundamentally anti-metaphysical—he aims to use the tools of mathematical logic to dissolve rather solve traditional philosophical problems—and it is precisely this point that is missed by his logically-minded contemporaries such as Hempel and Quine.