16.1: Possibility and necessity

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Kai von Fintel (2006: 20) defines Modality as “a category of linguistic meaning having to do with the expression of possibility and necessity.” Most if not all languages have lexical means for expressing these concepts, e.g. It is possible that… or It is necessary that…, but in this chapter we will focus our attention on the kinds of modality which can be expressed grammatically, e.g. by verbal affixation, particles, or auxiliary verbs. In English, modality is expressed primarily by modal auxiliaries: may, might, must, should, could, ought to, etc. (The phrase have to is often included in discussions of the English modals because it is a close synonym of must; but it does not have the unique syntactic distribution of a true auxiliary verb in English, and the syntactic differences sometimes have semantic consequences.)

In §16.2 we outline the range of modal meanings along two basic dimensions. The first of these is strength, or degree of certainty (e.g., must is said to be “stronger” than might). The second dimension is the type of certainty or lack of certainty which is being expressed, e.g. certainty of knowledge, requirement by an authority, etc. We will see that in many languages the same modal forms can be used for two or more different types of modality. We will see some evidence suggesting that such forms are polysemous, but also some reasons for challenging this assumption.

In §16.3 we outline a very influential analysis of modal operators as quantifiers, and show how this accounts for some of the puzzling observations discussed in §16.2. In §16.4 we discuss some of the variation across languages in terms of how modal meanings are packaged, and show how the quantifier analysis can account for these differences. In §16.5 we focus on one important type of modality, referred to as epistemic modality, which expresses degree of certainty in light of what the speaker knows. Some authors have claimed that epistemic modality is not part of the propositional content of the utterance; we review several kinds of evidence that support the opposite conclusion.