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Single Idea 14681
[filed under theme 10. Modality / A. Necessity / 6. Logical Necessity
]
Full Idea
With its freedom from the constraint of metaphysical possibility, logical necessity may be construed as accommodating all the axioms and rules of S5.
Gist of Idea
Logical necessity is free of constraints, and may accommodate all of S5 logic
Source
Nathan Salmon (The Logic of What Might Have Been [1989], III)
Book Ref
Salmon,Nathan: 'Metaphysics, Mathematics and Meaning' [OUP 2005], p.137
A Reaction
He goes on to raise problems for this simple thought. The big question: what are the limits of what is actually possible? Compare: what are the limits of what is imaginable? what are the limits of what is meaningfully sayable?
Related Idea
Idea 14679
Bizarre identities are logically but not metaphysically possible, so metaphysical modality is restricted [Salmon,N]
The
35 ideas
from Nathan Salmon
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14667
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System B has not been justified as fallacy-free for reasoning on what might have been
[Salmon,N]
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14668
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In B it seems logically possible to have both p true and p is necessarily possibly false
[Salmon,N]
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14669
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For metaphysics, T may be the only correct system of modal logic
[Salmon,N]
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14670
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Metaphysical (alethic) modal logic concerns simple necessity and possibility (not physical, epistemic..)
[Salmon,N]
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14671
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What is necessary is not always necessarily necessary, so S4 is fallacious
[Salmon,N]
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14672
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Possible worlds are maximal abstract ways that things might have been
[Salmon,N]
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14674
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Impossible worlds are also ways for things to be
[Salmon,N]
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14675
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Possible worlds just have to be 'maximal', but they don't have to be consistent
[Salmon,N]
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14673
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You can't define worlds as sets of propositions, and then define propositions using worlds
[Salmon,N]
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14676
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Nomological necessity is expressed with intransitive relations in modal semantics
[Salmon,N]
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14678
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Any property is attached to anything in some possible world, so I am a radical anti-essentialist
[Salmon,N]
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14677
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Metaphysical necessity is said to be unrestricted necessity, true in every world whatsoever
[Salmon,N]
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14679
|
Bizarre identities are logically but not metaphysically possible, so metaphysical modality is restricted
[Salmon,N]
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14680
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Logical possibility contains metaphysical possibility, which contains nomological possibility
[Salmon,N]
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14681
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Logical necessity is free of constraints, and may accommodate all of S5 logic
[Salmon,N]
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14682
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Denial of impossible worlds involves two different confusions
[Salmon,N]
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14687
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Without impossible worlds, how things might have been is the only way for things to be
[Salmon,N]
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14683
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Possible worlds rely on what might have been, so they can' be used to define or analyse modality
[Salmon,N]
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14689
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Necessity and possibility are not just necessity and possibility according to the actual world
[Salmon,N]
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14685
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Metaphysical necessity is NOT truth in all (unrestricted) worlds; necessity comes first, and is restricted
[Salmon,N]
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14690
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In the S5 account, nested modalities may be unseen, but they are still there
[Salmon,N]
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14688
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Without impossible worlds, the unrestricted modality that is metaphysical has S5 logic
[Salmon,N]
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14686
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S5 modal logic ignores accessibility altogether
[Salmon,N]
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14684
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A world is 'accessible' to another iff the first is possible according to the second
[Salmon,N]
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14692
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System B implies that possibly-being-realized is an essential property of the world
[Salmon,N]
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14691
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S5 believers say that-things-might-have-been-that-way is essential to ways things might have been
[Salmon,N]
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14693
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The unsatisfactory counterpart-theory allows the retention of S5
[Salmon,N]
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18885
|
Kripke and Putnam made false claims that direct reference implies essentialism
[Salmon,N]
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14742
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It can't be indeterminate whether x and y are identical; if x,y is indeterminate, then it isn't x,x
[Salmon,N]
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18886
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Frege's 'sense' solves four tricky puzzles
[Salmon,N]
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18887
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The perfect case of direct reference is a variable which has been assigned a value
[Salmon,N]
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14627
|
S4, and therefore S5, are invalid for metaphysical modality
[Salmon,N, by Williamson]
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18888
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Essentialism says some properties must be possessed, if a thing is to exist
[Salmon,N]
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18889
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Ostensive definitions needn't involve pointing, but must refer to something specific
[Salmon,N]
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18891
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Nothing in the direct theory of reference blocks anti-essentialism; water structure might have been different
[Salmon,N]
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