 Matters came to a head with the discovery of a proof (see Craig 1956) that the theoretical terms of a scientific theory are dispensable in the sense of it being possible to devise a functionally equivalent theory that does not make use of them. Did this not rob theoretical terms of their distinctive role and so support instrumentalism? The negative answer was twofold. As regards defending their utility, Carnap (1963b, §24) agreed with Hempel (1958) that in practice theoretical terms were indispensable in facilitating inductive relations between observational data. As regards the defense of their cognitive legitimacy, Carnap held that this demanded determining what he called their “experiential import”, namely, determining what specifically their empirical significance consisted in. It was for this purpose that Carnap came to employ Ramsey’s method of regimenting theoretical terms. Nowadays this so-called ramseyfication is often discussed as a means for expressing a position of “structural realism”, a position midway between fully-blown scientific realism and anti-realism and so sometimes thought to be of interest to Carnap. Carnap’s own concern with ramseyfication throws into relief not only the question of the viability of one of the Vienna Circle’s most forward-looking stances in the debate about theoretical terms—intending to avoid both realism and anti-realism—but also several other issues that bear on the question of which, if any, forms of Vienna Circle philosophy remain viable.