MoL-2009-07: A Dynamic Analysis of Epistemic Possibility

MoL-2009-07: Brumwell, Chris (2009) A Dynamic Analysis of Epistemic Possibility. [Report]

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Suppose you're on a peaceful raft floating down a quiet river, and all of a sudden your friend tells you that there might be crocodiles in the water. Neither of you knows for sure what's swimming around down there, and you glance over the side of your boat into the water. You don't see anything, and later find out that there have never been crocodiles in the river. Had your friend told you something true? After all, neither of you knew at the time that there weren't any crocodiles, so in a sense she was right to say it. Certainly, at least, you were told something non-trivial. But were you given any information? Did your friend's statement change your beliefs? You definitely thought twice about going in the water after what she said. If nothing else, she spoiled your peaceful boat ride. This thesis will address these and other questions about epistemic modality, focusing mostly on epistemic possibility. Modality is the feature of linguistic meaning that expresses necessity or possibility, and it has many different incarnations in natural language. Possibility can be expressed relative to certain bodies of rules, sets of beliefs, certain states of affairs, and much else. Epistemic modality expresses necessity or possibility relative to some body of knowledge or evidence. The assertion that `there might be crocodiles in the water' in the paragraph above expresses epistemic modality. In English, the modal expressions `might,' `may,' `must,' `perhaps,' `can,' `could,' `it is possible that,' and their close relatives often express epistemic modality. We refer to statements expressing epistemic modality as `epistemic modals'. Below, we will argue for a non-truth conditional analysis of epistemic modality, and will further argue that the content of epistemic modals has a non-informative dimension. Both of our analyses will be presented in a dynamic semantics framework. While this thesis is primarily an analysis of epistemic modality, it can also be seen as a case study in the usefulness of the dynamic perspective on natural language. Hence, it is both an argument for a particular view of epistemic modality and an argument for a dynamic theory of meaning. The thesis is divided into three main parts. First, we argue for a non-truth conditional analysis of epistemic modality. In this section, we also consider two popular truth conditional theories of epistemic modality. Our non-truth conditional theory is developed from a dynamic theory of meaning and communication, both of which are sketched in this section. In the second part, we argue that the content of epistemic modals has a noninformative dimension. Specifically, we hold that this non-informative content of epistemic modals consists in their ability to draw attention or awareness towards certain possibilities. We support this claim with intuitive considerations regarding communication and conversation as well as data regarding universally quantified epistemic modal formulas and epistemic modals used to answer questions. Our considerations regarding communication and conversation develop the informal idea of a `salient possibility', a notion we later formalize and put it to crucial use in our formal theory of questions and answers, which accounts for both informative and non-informative answers to questions. We make some brief remarks concerning what the notion of a non-informative answer entails for the semantics of questions. Third, we argue that there are cognitive aspects of the non-informative content of epistemic modals. Rather than simply being a tool for the management and organization of a discourse, we will argue that the non-informative content of epistemic modals plays a significant role in belief and thought. Here, we will focus mostly on data involving epistemic modals in attitude reports, though we also briefly discuss epistemic modals used to give advice and warnings. Below, we assume minimal exposure to the central concepts of dynamic semantics. However, we assume some knowledge of possible worlds semantics and pragmatics and a modest understanding of the semantics and pragmatics of questions.

Item Type: Report
Report Nr: MoL-2009-07
Series Name: Master of Logic Thesis (MoL) Series
Year: 2009
Date Deposited: 12 Oct 2016 14:38
Last Modified: 12 Oct 2016 14:38

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