 Karttunen’s (1973) account is of interest not only for its triptych of plugs, holes and filters, but also because it sets the background for a crucial shift of perspective in Karttunen (1974), and thence to the dynamic approaches to presupposition that have been dominant in recent years. What remained unclear in the 1973 paper was the motivation for filtering, i.e. why presuppositions should be filtered out when entailed by other material. Karttunen (1974) suggests an alternative conception based on the idea of local contexts of evaluation. The idea is that the parts of a sentence are not necessarily evaluated with respect to the same context as that in which the sentence as a whole is evaluated: a local context may contain more information than the global context. For example, when evaluating a conjunction, the second conjunct is evaluated in a local context which contains not only the information in the global context, but also whatever information was given by the first conjunct. Karttunen (1974) defines local contexts of evaluation for a range of constructions, and suggests the following requirement: presuppositions always need to be entailed (or “satisfied”, as he put it) in the local context in which the trigger is evaluated. Given this requirement, the overall presuppositions of a sentence will just be whatever propositions must be in a context of an utterance in order to guarantee that the requirements associated with presupposition triggers are satisfied in their local contexts of interpretation.