"Now that you mention it, I wonder...": Awareness, Attention, Assumption
Tikitu de Jager

Abstract:
This dissertation applies the notion of unawareness to problems of
formal se- mantics and pragmatics. Unawareness is an epistemic
attitude that has recently raised a lot of interest in epistemic logic
circles, as well as in what we might call "formal epistemic
economics". Informally it is closely related to inattention: an
(epistemic) agent may attend to possibilities (that is, consciously
represent them and reason about them in deliberation) or be unaware of
them (not give them conscious representation; not have them play any
role in deliberation).  While unawareness implies lack of knowledge,
it differs from previous notions of uncertainty in its formal and
conceptual properties; most importantly, an agent unaware of some
proposition $p$ does not know that $p$, but he also does not know that
she does not know that $p$.
  In Chapter 1 I describe the informal notions of unawareness and
inattention and give some examples suggesting their applicability to
formal semantics and pragmatics; these use a notion of assumption that
does not feature in the existing formal theories. I give a short
survey of existing models, and argue that none such is appropriate for
the linguistic problems; the rest of the dissertation tries to fill
the resulting gap in the market.
  In Chapter 2 I introduce the formal terminology of
unawareness/inattention and assumption, and a simple logic with a
static possible-worlds semantics.  Chapter 3 gives a dynamic
semantics, allowing us to describe changes in awareness, and argues
that this is the most relevant framework for linguistic applications
of the notions. Chapter 4 is a case study, applying unawareness to
so-called "Sobel sequences", a long-standing puzzle concerning the
semantics of counterfactuals.
  Chapter 5 takes a different tack, developing a decision-theoretic
apparatus enhanced with a representation of unawareness and
assumption. The aim is to extend the range of decision-theoretic
pragmatics, which describes various forms of pragmatic inference as
rational behaviour according to decision- theoretic norms, to cover
unawareness phenomena.
  Chapter 6 gives a rather different unawareness model, based on data
semantics. This captures various kinds of defeasible inference which
owe their defeasible nature to unawareness (typically inference from
evidence to "must"- statements, which are only justified under limited
awareness of the domain of possibility).
  Finally, Chapter 7 summarises the approach here presented and offers
some speculation about possible future extensions of the ideas.




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