The lecture will consider Michael Dummett’s contention, in The Logical Basis of Metaphysics, that semantic theories should be formulated in such a way that the logic of the object-language is maximally insensitive to the logic of the meta-language. The controversy over the status of the Barcan formula and its converse in quantified modal logic will be taken as a case study. It will be argued that the insensitivity in question is a less desirable feature of a semantic theory than Dummett suggests.