a unified theory of granularity, vagueness and approximation
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A Unified Theory of Granularity, Vagueness and Approximation. Thomas Bittner and Barry Smith Northwestern University NCGIA and SUNY Buffalo. Overview. Introduction Vagueness and truth Granular partitions and context Vagueness and granular partitions Boundaries and contexts Approximation - PowerPoint PPT PresentationTRANSCRIPT
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A Unified Theory of Granularity, Vagueness and Approximation
Thomas Bittner and Barry Smith
Northwestern University
NCGIA and SUNY Buffalo
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Overview
1. Introduction
2. Vagueness and truth
3. Granular partitions and context
4. Vagueness and granular partitions
5. Boundaries and contexts
6. Approximation
7. Conclusions
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Judging subject
Semantic theorist
Partition theoristwants to determine the truth of J by using partition theory
wants to determine the truth of J by using reference semantics
J = ‘We will cross the boundary of Mount Everest within the next hour’
Three people and a mountain
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Vagueness
Where is the boundary of Everest?
Boundary is subject to vagueness
The boundary of Everest IS vague: broad or fuzzy boundary
Vague objects and boundariesas ontological primitives
Vagueness is a semantic propertyThere is a multitude of equally good crisp candidates of reference
Extend semantics: supervaluation
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Supervaluation (Fine 1975)
• Extension of reference semantics to vagueness
• Takes multiplicity of candidate referents of vague names into account
• S = ‘X is a part of Mount Everest’
– Truth value of S is determined for all candidate referents of ‘Mount Everest’
– S is supertrue if it is true for all candidates– S is superfalse if it is true for no candidate
– S is indeterminate otherwise
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Vagueness and truth
S = ‘We will cross the boundary of Everest within the next hour’
S is superfalse
S is indeterminate
S is supertrue
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Vagueness and truth
S = ‘We will cross the boundary of Everest within the next hour’
S is supertrue
?
?
?
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Sentences vs. Judgments (Smith & Brogaard 2001)
Sentence: ‘There is no beer in the glass.’
Drunkard:Hygiene inspector:
Judgments = Sentence + Context
(super) trueThe glass does not contain (drinkable amounts of) beer
(super) falseThe glass contains tinyamounts of beer, microbes, mold, …
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Granular partitions a formally tractable proxy for the notion of
context
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Theory of granular partitions
• There is a projective relation between cognitive subjects and reality
Major assumptions:
• Humans ‘see’ reality through a grid
• The ‘grid’ is usually not regular and raster shaped
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Projection of cells
…
Wyoming
Idaho
Montana
…
Cell structure North AmericaProjection
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• no counties • no county boundaries
Part of the surface of the Earth photographed from space
Projection establishes fiat boundaries
Cell structure
Map =Representationof cell structure
County boundaries in reality
P
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Partitions and contextJ = (‘There is no beer in the glass’, Partition)
Glass
Beer
Glass
Beer
probe
Cell ‘Beer’ does projectCell ‘Beer’ does not project
J is true in this context J is false in this context
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Judgments about mereological structure
J = (‘X is part of Y’, Pt) = true
Y
X
YX
U V
VU
Labeling ofnames in S onto cells in Pt
projection
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Vagueness and granular partitions
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Crisp and vague projection
…Montana
…
crisp
Himalayas
EverestvagueP1
Pn
Vague reference is always reference to fiat boundaries!
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Vague judgments about mereological structure
J = (‘XV is part of Y’, PtV) = supertrue
Y
X
Labeling ofnames in S onto cells in Pt
P1
Pn
YX )()(
),...,()( 11
YPnXPn
YPXP
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Vagueness and truth
J = (‘We will cross the boundary of Everest within the next hour’, Pt)
?
?
?
Whether or not indeterminacy can arise depends on the projection of the boundaries!
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Boundaries and contexts
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Boundaries and contexts
We distinguish:
contexts in which our use of a vague term brings:
1. a single crisp fiat boundary
2. a multiplicity of crisp fiat boundaries
into existence
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The single crisp boundary case
J = (‘This is the boundary of Mount Everest’, Pt)
• The judging subject must have the authority (the partitioning power) to impose this boundary
e.g., she is a member of some government agency
Vagueness is resolved. J has a determinate truth value
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The multiple boundary case
The subject (restaurant owner) judges:J = (‘The boundary of the smoking zone goes here’, Pt)while vaguely pointing across the room.
Vague projection brings a multitude of boundary candidates into existence
Truth-value indeterminacy can potentially arise
To show: naturally occurring contexts are such that truth-value indeterminacy does not arise.
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The multiple boundary case
Claim:
The judgment can be uttered only in contexts
(1) Where it is precise enough to be (super)true
(2) but: not precise enough for indeterminacy to arise
The subject (restaurant owner) judges:J = (‘The boundary of the smoking zone goes here’, Pt)while vaguely pointing across the room.
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The multiple boundary case
Context 1:
To advise the staff where to put the ashtrays
The projection must be just precise enough to determineon which table to put an ashtray
The subject (restaurant owner) judges:J = (‘The boundary of the smoking zone goes here’, Pt)while vaguely pointing across the room.
No truth-value indeterminacy
Context 2:
To describe where nicotinemolecules are
truth-value indeterminacy can potentially occur
But: nobody can seriously utter such a judgment in naturally occurring contexts
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Approximation;or
how to make vague reference in a determinate fashion
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Boundaries limiting vagueness
S = ‘We will cross the boundary of Everest within the next hour’
in one hour,interior boundary
Exterior b.now
candidate i
candidate k
direction of travel
core
Where-the-boundary-candidates are
Two partitions:
(1) a vague partition
Carving out candidatereferents for the vague name ‘Everest’
(2) a partition projecting along the way ahead
Limits admissible candidate referents for ‘Everest’
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Approximating judgments
S = ‘We will cross the boundary of Everest within the next hour’
J = (S, PtV, PtR)
in one hour,interior boundary
Exterior b.now
candidate icandidate k
direction of travel
core
Where-the-boundary-candidates are
Truth of J depends on the relationshipsbetween PtV and PtR
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Truth of approximating judgments
An approximating judgment J = (S, PtV, PtR) is:
Supertrue: all candidate referents projected onto by PtV are within the limits given by PtR
Superfalse: no candidate referent projected onto by PtV is within the limits given by PtR
Indeterminate: some candidate referents projected onto by PtV are within the limits given by PtR and others are not.
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Truth-value indeterminacy of approximating judgments …
?
… does not actually occur in naturally occurring contexts
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Truth value indeterminacy ??Why can ‘We will cross the boundary of Everest within the next hour’ not be judged in these contexts ?
?
?
Judger has the freedomto choose appropriatedelimiting boundaries.
Why should she use ridiculous ones which do not make sense ?
Why should she use ones subject to indeterminacy ?
?
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Higher order vagueness
Boundaries that delimit vagueness of reference
What if these boundaries are subject to vagueness themselves?
Higher-order vagueness
S = ‘We will cross the boundary of Everest within the next hour or so’
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Higher order vagueness
To show:
Higher order vagueness does not cause truth-valueindeterminacy in naturally occurring contexts
S = ‘We will cross the boundary of Everest within the next hour or so’
(1) those which re-use existing boundaries
(2) those which create new fiat boundaries
Two classes of contexts:
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Re-using existing boundaries
J = (‘The area ofbad weather extends over parts of Wyoming,Montana, Idaho, andUtah’, PtV, PtR)
The re-used boundaries are crisp.
No truth value indeterminacy
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Create new fiat boundaries
exterior candidate
boundary
core
interior boundary
exterior boundary
S = ‘We will cross the boundary of Everest within the next hour or so’
Multiplicity ofcandidatereferents
Judging subject mustchoose limiting boundariesmuch crisper than the degree of vagueness theylimit
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Conclusions
• Theory of granular partitions provides a tool to understand granularity, vagueness, indeterminacy and the relationships between them
• Context is critical when analyzing truth-values of judgments
• In naturally occurring contexts truth-value indeterminacy does not occur
• Formalism – see paper
• Partition-theoretic solution to the Sorites paradoxes – see paper