The purpose of this study is to analyze the differences between deontic modality and imperative sentences using possible worlds semantics, a framework proposed by Kratzer (1981, 1991, 2012). This study describes whether the preceding studies are appropriate or not. Modality refers to the mental attitude of a speaker and the condition of facts or matters. Deontic modality and imperatives request a hearer to act according to what a speaker says or to obey rules. Both are similar, but have some differences in semantics. Previous studies discussed differences between deontic modal verbs and imperatives using the framework of Kratzer. Imperative sentences and deontic modal sentences are similar to directives usage. For instance, one previous study concluded that the conversational background of imperatives is totally realistic conversational background. What’s more, imperatives did not have a truth value, so the framework could not be used appropriately.
Deontic modality and imperative sentences are different with respect to semantic structures in possible worlds. The conversational backgrounds of imperatives are bouletic conversational backgrounds. In this study, an imperative shows both a speaker’s wish and the truth value; this is a big difference from prior research proposals. Imperative sentences satisfy the set of possible worlds which include the speaker’s wishes and the fact that deontic propositions can be true. On the other hand, a deontic modality has a truth value in terms of the criterion of necessity. In the end, both of the semantic structures are shown in this study.