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Single Idea 14685
[filed under theme 10. Modality / A. Necessity / 5. Metaphysical Necessity
]
Full Idea
A mythology gave us the idea that metaphysical necessity is truth in every world whatsoever, without restriction. But the notion of metaphysical modality comes first, and, like every notion of modality, it is restricted.
Gist of Idea
Metaphysical necessity is NOT truth in all (unrestricted) worlds; necessity comes first, and is restricted
Source
Nathan Salmon (The Logic of What Might Have Been [1989], IV)
Book Ref
Salmon,Nathan: 'Metaphysics, Mathematics and Meaning' [OUP 2005], p.141
The
27 ideas
from 'The Logic of What Might Have Been'
14669
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For metaphysics, T may be the only correct system of modal logic
[Salmon,N]
|
14667
|
System B has not been justified as fallacy-free for reasoning on what might have been
[Salmon,N]
|
14668
|
In B it seems logically possible to have both p true and p is necessarily possibly false
[Salmon,N]
|
14670
|
Metaphysical (alethic) modal logic concerns simple necessity and possibility (not physical, epistemic..)
[Salmon,N]
|
14671
|
What is necessary is not always necessarily necessary, so S4 is fallacious
[Salmon,N]
|
14674
|
Impossible worlds are also ways for things to be
[Salmon,N]
|
14672
|
Possible worlds are maximal abstract ways that things might have been
[Salmon,N]
|
14675
|
Possible worlds just have to be 'maximal', but they don't have to be consistent
[Salmon,N]
|
14673
|
You can't define worlds as sets of propositions, and then define propositions using worlds
[Salmon,N]
|
14676
|
Nomological necessity is expressed with intransitive relations in modal semantics
[Salmon,N]
|
14678
|
Any property is attached to anything in some possible world, so I am a radical anti-essentialist
[Salmon,N]
|
14677
|
Metaphysical necessity is said to be unrestricted necessity, true in every world whatsoever
[Salmon,N]
|
14679
|
Bizarre identities are logically but not metaphysically possible, so metaphysical modality is restricted
[Salmon,N]
|
14681
|
Logical necessity is free of constraints, and may accommodate all of S5 logic
[Salmon,N]
|
14680
|
Logical possibility contains metaphysical possibility, which contains nomological possibility
[Salmon,N]
|
14682
|
Denial of impossible worlds involves two different confusions
[Salmon,N]
|
14687
|
Without impossible worlds, how things might have been is the only way for things to be
[Salmon,N]
|
14683
|
Possible worlds rely on what might have been, so they can' be used to define or analyse modality
[Salmon,N]
|
14689
|
Necessity and possibility are not just necessity and possibility according to the actual world
[Salmon,N]
|
14690
|
In the S5 account, nested modalities may be unseen, but they are still there
[Salmon,N]
|
14685
|
Metaphysical necessity is NOT truth in all (unrestricted) worlds; necessity comes first, and is restricted
[Salmon,N]
|
14684
|
A world is 'accessible' to another iff the first is possible according to the second
[Salmon,N]
|
14688
|
Without impossible worlds, the unrestricted modality that is metaphysical has S5 logic
[Salmon,N]
|
14686
|
S5 modal logic ignores accessibility altogether
[Salmon,N]
|
14691
|
S5 believers say that-things-might-have-been-that-way is essential to ways things might have been
[Salmon,N]
|
14692
|
System B implies that possibly-being-realized is an essential property of the world
[Salmon,N]
|
14693
|
The unsatisfactory counterpart-theory allows the retention of S5
[Salmon,N]
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