Consider the class of contextually sensitive expressions whose context invariant meanings arguably do not suffice to secure semantic values in context. Demonstratives and demonstrative pronouns are the examples of such expressions that have received the most attention from philosophers. However, arguably this class of contextually sensitive expressions includes among other expressions modals, conditionals, tense, gradable adjectives, possessives, ‘only’, quantifiers, and expressions that take implicit arguments (e.g. ‘ready’ in sentences like ‘Molly is ready.’). Most theorists, including me, think that since the (...) context invariant meanings of such expressions do not by themselves secure semantic values in context for these expressions, they must be supplemented in some way in context in order to secure semantic values in context. For this reason, I call these expressions supplementives. I just said that supplementives need some sort of supplementation to secure semantic values in context. Of course, the question of what form the supplementation in context takes is controversial. For example, ever since Kaplan claimed that the semantic value of a demonstrative or demonstrative pronoun in context is the demonstratum of its associated demonstration, there has been a lively controversy over whether that or some other account is the correct one. Call an account of how a given supplementive secures a semantic value in context a metasemantics for the supplementive. In King [2018] I argue that all supplementives have felicitous uses in which they haven’t been assigned unique semantic values in context. This conclusion is somewhat surprising, since many uses of supplementives in which they have not been assigned unique semantic values in context are quite infelicitous. I call felicitous uses of supplementives in which they haven’t been assigned unique semantic values in context instances of felicitous underspecification. The central idea is that in cases of felicitous underspecification, supplementives get assigned a range of candidates for being their semantic values in contexts rather than being assigned unique semantic values in contexts. Consider an example. Glenn and I are out surfing at Lost Winds beach. There are some surfers to our south stretching a quarter mile or so down the beach. I notice that some surfers in an ill-defined group to our immediate south are getting incredible rides. I say to Glenn looking south toward them ‘Those guys are good.’ It seems easy to imagine that nothing in the context of utterance determines a unique group of surfers as the semantic value in context of ‘Those guys’. For example, it is easy to imagine that I didn’t intend any specific, unique group to be the semantic value in context. Instead, there is a range of overlapping groups that are legitimate candidates for being the semantic value in context of ‘Those guys’. Nonetheless, my utterance is felicitous: Glenn had no qualms about my utterance and took it to be impeccably acceptable. So this is an instance of felicitous underspecification. As its title suggests, felicitous underspecification is the main topic of the present book. Here is a summary of what is in each chapter. Chapter 1 provides examples of felicitous underspecification for a variety of supplementives. In each case of felicitous underspecification considered in Chap. 1, I say how I think conversational participants update the Stalnakerian common ground after accepting the utterance of the sentence containing a felicitous underspecified use of a supplementive. I do so without there formulating a principle that determines the updates in question. In Chap. 2, I formulate such a principle and illustrate its predictions with some of the cases of felicitous underspecification considered in Chap. 1. I claim the principle correctly predicts the updates discussed in Chap. 1. In Chap. 3, I consider and discuss the mechanism that I claim associates ranges of candidate semantic values in context with felicitous underspecified uses of supplementives. In Chap. 4, I discuss cases in which felicitous underspecified uses of supplementives are embedded in certain ways: under negation, and under ‘believes’ and ‘doubts’. In Chap. 5 I take up I take up the question of why sentences containing felicitous underspecified uses of supplementives are felicitous in the contexts in which they are uttered. In particular, I formulate a notion of a context being appropriate for an LF, where an LF is felicitous in a context only if the context is appropriate for the LF. In particular, an LF ϕ containing a use of an underspecified supplementive in a context c will be felicitous only if c is appropriate for ϕ. In Chap. 6, I take up some problems that arise with underspecified uses of pronouns, demonstratives and possessives and consider revising the appropriateness condition of Chap. 5. (shrink)