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Single Idea 21719
[filed under theme 5. Theory of Logic / I. Semantics of Logic / 5. Extensionalism
]
Full Idea
With the principle of extensionality anything true of one propositional functions will be true of every coextensive one.
Gist of Idea
Extensionalism means what is true of a function is true of coextensive functions
Source
Bernard Linsky (Russell's Metaphysical Logic [1999], 6.3)
Book Ref
Linsky,Bernard: 'Russell's Metaphysical Logic' [CSLI 1999], p.97
The
13 ideas
from Bernard Linsky
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18774
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Definite descriptions, unlike proper names, have a logical structure
[Linsky,B]
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18776
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Contextual definitions eliminate descriptions from contexts
[Linsky,B]
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21704
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'Impredictative' definitions fix a class in terms of the greater class to which it belongs
[Linsky,B]
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21705
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Reducibility says any impredicative function has an appropriate predicative replacement
[Linsky,B]
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21703
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Types are 'ramified' when there are further differences between the type of quantifier and its range
[Linsky,B]
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21714
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The ramified theory subdivides each type, according to the range of the variables
[Linsky,B]
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21713
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Did logicism fail, when Russell added three nonlogical axioms, to save mathematics?
[Linsky,B]
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21715
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For those who abandon logicism, standard set theory is a rival option
[Linsky,B]
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21719
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Extensionalism means what is true of a function is true of coextensive functions
[Linsky,B]
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21721
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Higher types are needed to distinguished intensional phenomena which are coextensive
[Linsky,B]
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21723
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The task of logicism was to define by logic the concepts 'number', 'successor' and '0'
[Linsky,B]
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21727
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Definite descriptions theory eliminates the King of France, but not the Queen of England
[Linsky,B]
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21729
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Construct properties as sets of objects, or say an object must be in the set to have the property
[Linsky,B]
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