Introduction to Metaphysics

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Introduction to Metaphysics Alexander Bird
What are Necessity and Possibility?
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necessary
what must be
There is no largest prime number Nothing may be
red and green all over
possible
what might have been
David Cameron is not the next Prime minister The
Solar System had only six planets
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note We are talking here is metaphysical not
epistemic notions
I cannot find my keys - it is possible that I
left them at home There are six possible ways
for a die to land You were lucky - the train
was on time, but it could have been late
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true
necessarily true
true but possibly false
false
false but possibly true
necessarily false
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some symbolism
necessarily p ?p possibly p ?p
therefore
it is contingent that p ?p ?p
?p ? p
p ? ?p
?p ? ?p
?p ? ?p
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what are necessity and possibility?
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are necessity and possibility features of things
and their properties?
(note also extreme or Megarian actualism no
possibility or actuality)
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Lewiss modal realism
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possible worlds are useful for understanding fic
tions propositions properties counterfactuals caus
ation
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Sherlock Holmes is a cocaine addict is true
fictions propositions properties counterfactuals c
ausation
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fictions propositions properties counterfactuals c
ausation
the proposition p the set of possible worlds
where p is true
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fictions propositions properties counterfactuals c
ausation
the property F the set of ordered pairs ltx,
wgt where x is F at w
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why should anyone believe in possible worlds?
after all, we cannot causally interact with other
possible worlds
c.f. knowledge of mathematics
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why should anyone believe in possible worlds?
why should anyone believe in any theory positing
unobservable entities?
because the theory gives a an explanation of the
phenomena that is simple and unifying
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Fictionalism
fictional entities non-actual possible
objects possible worlds abstract objects
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"There is a (non-actual) possible world at which
there are blue swans "There is a brilliant
detective at 221b Baker Street"
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There is a (non-actual) possible world at which
there are blue swans
true logical form
FPW(There is a (non-actual) possible world at
which there are blue swans)
FPW(p) according to the fiction of possible
worlds, p
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Sherlock Holmes is a cocaine addict
FX(p) In the nearest possible world where (most
of) the fictional writings X are true, p
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In the nearest possible world where SH stories
are true, Sherlock Holmes is a cocaine addict
FX(p) In the nearest possible world where (most
of) the fictional writings X are true, p
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In the nearest possible world where the fiction
of possible worlds is true, in the nearest
possible world where SH stories are true,
Sherlock Holmes is a cocaine addict
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fictions
possible worlds
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further reading
Stanford Encyclopedia of Philosophy http//www.seo
p.leeds.ac.uk/entries/fictionalism-modal/
Routledge Encyclopedia of Philosophy Online
http//www.rep.routledge.com/ possible
worlds Lewis, David Kellogg