Carnap on theoretical terms: structuralism without metaphysics

Both realists and instrumentalists have found it difficult to understand (much less accept) Carnap’s developed view on theoretical terms, which attempts to stake out a neutral position between realism and instrumentalism. I argue that Carnap’s mature conception of a scientific theory as the conjunction of its Ramsey sentence and Carnap sentence can indeed achieve this neutral position. To see this, however, we need to see why the Newman problem raised in the context of recent work on structural realism is no problem for Carnap’s conception; and we also need to locate Carnap’s work on theoretical terms within his wider program of Wissenschaftslogik or the logic of science.