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Single Idea 11002
[filed under theme 10. Modality / A. Necessity / 2. Nature of Necessity
]
Full Idea
C.I.Lewis's S4 system develops a sense of necessity as 'provability' in some fairly informal sense.
Gist of Idea
Equating necessity with informal provability is the S4 conception of necessity
Source
report of C.I. Lewis (works [1935]) by Stephen Read - Thinking About Logic Ch. 4
Book Ref
Read,Stephen: 'Thinking About Logic' [OUP 1995], p.118
The
15 ideas
from C.I. Lewis
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5828
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Extension is the class of things, intension is the correct definition of the thing, and intension determines extension
[Lewis,CI]
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6556
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If anything is to be probable, then something must be certain
[Lewis,CI]
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21500
|
We rely on memory for empirical beliefs because they mutually support one another
[Lewis,CI]
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21498
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Congruents assertions increase the probability of each individual assertion in the set
[Lewis,CI]
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21501
|
If we doubt memories we cannot assess our doubt, or what is being doubted
[Lewis,CI]
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9357
|
Excluded middle is just our preference for a simplified dichotomy in experience
[Lewis,CI]
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9358
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There are several logics, none of which will ever derive falsehoods from truth
[Lewis,CI]
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9362
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Necessary truths are those we will maintain no matter what
[Lewis,CI]
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9361
|
We have to separate the mathematical from physical phenomena by abstraction
[Lewis,CI]
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9363
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Science seeks classification which will discover laws, essences, and predictions
[Lewis,CI]
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9364
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Names represent a uniformity in experience, or they name nothing
[Lewis,CI]
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9365
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We can maintain a priori principles come what may, but we can also change them
[Lewis,CI]
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7803
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Modal logic began with translation difficulties for 'If...then'
[Lewis,CI, by Girle]
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11002
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Equating necessity with informal provability is the S4 conception of necessity
[Lewis,CI, by Read]
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7791
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The simplest of the logics based on possible worlds is Lewis's S5
[Lewis,CI, by Girle]
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