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Single Idea 13845
[filed under theme 5. Theory of Logic / A. Overview of Logic / 4. Pure Logic
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Full Idea
I don't believe English is by nature classical or intuitionistic etc. These are abstractions made by logicians. Logicians attend to numerous different objects that might be served by 'If...then', like material conditional, strict or relevant implication.
Gist of Idea
The various logics are abstractions made from terms like 'if...then' in English
Source
Ian Hacking (What is Logic? [1979], §15)
Book Ref
'A Philosophical Companion to First-Order Logic', ed/tr. Hughes,R.I.G. [Hackett 1993], p.250
A Reaction
The idea that they are 'abstractions' is close to my heart. Abstractions from what? Surely 'if...then' has a standard character when employed in normal conversation?
The
19 ideas
from Ian Hacking
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7447
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Probability was fully explained between 1654 and 1812
[Hacking]
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7448
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Probability is statistical (behaviour of chance devices) or epistemological (belief based on evidence)
[Hacking]
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7459
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Follow maths for necessary truths, and jurisprudence for contingent truths
[Hacking]
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7449
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Epistemological probability based either on logical implications or coherent judgments
[Hacking]
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7450
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In the medieval view, only deduction counted as true evidence
[Hacking]
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7451
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Formerly evidence came from people; the new idea was that things provided evidence
[Hacking]
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7452
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An experiment is a test, or an adventure, or a diagnosis, or a dissection
[Hacking, by PG]
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7454
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Gassendi is the first great empiricist philosopher
[Hacking]
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13833
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'Thinning' ('dilution') is the key difference between deduction (which allows it) and induction
[Hacking]
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13834
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Gentzen's Cut Rule (or transitivity of deduction) is 'If A |- B and B |- C, then A |- C'
[Hacking]
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13835
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Only Cut reduces complexity, so logic is constructive without it, and it can be dispensed with
[Hacking]
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13837
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With a pure notion of truth and consequence, the meanings of connectives are fixed syntactically
[Hacking]
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13838
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A decent modern definition should always imply a semantics
[Hacking]
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13839
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Perhaps variables could be dispensed with, by arrows joining places in the scope of quantifiers
[Hacking]
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13843
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If it is a logic, the Löwenheim-Skolem theorem holds for it
[Hacking]
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13840
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First-order logic is the strongest complete compact theory with Löwenheim-Skolem
[Hacking]
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13844
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A limitation of first-order logic is that it cannot handle branching quantifiers
[Hacking]
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13842
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Second-order completeness seems to need intensional entities and possible worlds
[Hacking]
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13845
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The various logics are abstractions made from terms like 'if...then' in English
[Hacking]
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