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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