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Single Idea 5736
[filed under theme 7. Existence / D. Theories of Reality / 8. Facts / a. Facts
]
Full Idea
Some philosophers say that modal facts cannot be expressed either by name/predicate language, or by first-order predicate calculus, or even by second-order logic.
Clarification
'Modal' facts concern possibility and necessity
Gist of Idea
No sort of plain language or levels of logic can express modal facts properly
Source
Joseph Melia (Modality [2003], Ch.2)
Book Ref
Melia,Joseph: 'Modality' [Acumen 2003], p.21
A Reaction
If 'possible' were a predicate, none of this paraphernalia would be needed. If possible worlds are accepted, then the quantifiers of first-order predicate calculus will do the job. If neither of these will do, there seems to be a problem.
The
17 ideas
from 'Modality'
5734
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Possible worlds make it possible to define necessity and counterfactuals without new primitives
[Melia]
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5732
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'De re' modality is about things themselves, 'de dicto' modality is about propositions
[Melia]
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5739
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Sometimes we want to specify in what ways a thing is possible
[Melia]
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5742
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In possible worlds semantics the modal operators are treated as quantifiers
[Melia]
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5743
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If possible worlds semantics is not realist about possible worlds, logic becomes merely formal
[Melia]
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5740
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Second-order logic needs second-order variables and quantification into predicate position
[Melia]
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5741
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If every model that makes premises true also makes conclusion true, the argument is valid
[Melia]
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5735
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Maybe names and predicates can capture any fact
[Melia]
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5736
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No sort of plain language or levels of logic can express modal facts properly
[Melia]
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5737
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Predicate logic has connectives, quantifiers, variables, predicates, equality, names and brackets
[Melia]
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5738
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We may be sure that P is necessary, but is it necessarily necessary?
[Melia]
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5744
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First-order predicate calculus is extensional logic, but quantified modal logic is intensional (hence dubious)
[Melia]
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5746
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The Identity of Indiscernibles is contentious for qualities, and trivial for non-qualities
[Melia]
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5748
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We accept unverifiable propositions because of simplicity, utility, explanation and plausibility
[Melia]
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5749
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Possible worlds could be real as mathematics, propositions, properties, or like books
[Melia]
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5750
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Consistency is modal, saying propositions are consistent if they could be true together
[Melia]
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5751
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The truth of propositions at possible worlds are implied by the world, just as in books
[Melia]
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