 Consider that Carnap (1939, 1956b) admitted as legitimate theoretical terms that are implicitly defined in calculi that are only partially interpreted by correspondence rules between some select calculus terms and expressions belonging to an observational language (via non-eliminative reductions). The problem was that mere confirmability was simply too weak a criterion to rule out some putative metaphysical claims. Moreover, this problem arose for both the statement-based approach to the criterion (taken by Carnap in 1928, by Wittgenstein in 1929/30, and by Ayer both in the first (1936) and the second editions (1946) of Language Truth and Logic) and for the term-based approach (taken by Carnap since 1932). For the former approach, the problem was that the empirical legitimacy of statements obtained via indirect testing also transferred to any expressions that could be truth-functionally conjoined to them (for instance, by the rule of ‘or’-introduction). Statements thus became empirically significant, however vacuous they had been on their own. For the term-based approach, the problem was that, given the non-eliminability of dispositional and theoretical terms, empirical significance was no longer ascribable to individual expressions in isolation but became a holistic affair, with little guarantee in turn for the empiricist legitimacy of all the terms now involved.