What ‘must’ adds

  • Matthew MandelkernEmail author
Open Access


There is a difference between the conditions in which one can felicitously use a ‘must’-claim like (1-a) and those in which one can use the corresponding claim without the ‘must’, as in (1-b):
$$\begin{aligned}&\hbox {(1)} \,\,\quad \hbox {a. It must be raining out}.\\&\qquad \,\,\, \hbox {b. It is raining out}. \end{aligned}$$
It is difficult to pin down just what this difference amounts to. And it is difficult to account for this difference, since assertions of  \(\ulcorner \)Must p\(\urcorner \)  and assertions of p alone seem to have the same basic goal: namely, communicating that p is true. In this paper I give a new account of the conversational role of ‘must’. I begin by arguing that a ‘must’-claim is felicitous only if there is a shared argument for the proposition it embeds. I then argue that this generalization, which I call Support, can explain the more familiar generalization that ‘must’-claims are felicitous only if the speaker’s evidence for them is in some sense indirect. Finally, I propose a pragmatic derivation of Support as a manner implicature.


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Authors and Affiliations

  1. 1.All Souls CollegeUniversity of OxfordOxfordUK

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