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10845
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To be true a sentence must express a proposition, and not be ambiguous or vague or just expressive [Lewis]
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Full Idea:
Sentences or assertions can be derivately called true, if they succeed in expressing determinate propositions. A sentence can be ambiguous or vague or paradoxical or ungrounded or not declarative or a mere expression of feeling.
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From:
David Lewis (Forget the 'correspondence theory of truth' [2001], p.276)
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A reaction:
Lewis has, of course, a peculiar notion of what a proposition is - it's a set of possible worlds. I, with my more psychological approach, take a proposition to be a particular sort of brain event.
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13342
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Carnap defined consequence by contradiction, but this is unintuitive and changes with substitution [Tarski on Carnap]
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Full Idea:
Carnap proposed to define consequence as 'sentence X follows from the sentences K iff the sentences K and the negation of X are contradictory', but 1) this is intuitively impossible, and 2) consequence would be changed by substituting objects.
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From:
comment on Rudolph Carnap (The Logical Syntax of Language [1934], p.88-) by Alfred Tarski - The Concept of Logical Consequence p.414
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A reaction:
This seems to be the first step in the ongoing explicit discussion of the nature of logical consequence, which is now seen by many as the central concept of logic. Tarski brings his new tool of 'satisfaction' to bear.
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13251
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Each person is free to build their own logic, just by specifying a syntax [Carnap]
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Full Idea:
In logic, there are no morals. Everyone is at liberty to build his own logic, i.e. his own form of language. All that is required is that he must state his methods clearly, and give syntactical rules instead of philosophical arguments.
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From:
Rudolph Carnap (The Logical Syntax of Language [1934], §17), quoted by JC Beall / G Restall - Logical Pluralism 7.3
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A reaction:
This is understandable, but strikes me as close to daft relativism. If I specify a silly logic, I presume its silliness will be obvious. By what criteria? I say the world dictates the true logic, but this is a minority view.
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14212
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A consistent theory just needs one model; isomorphic versions will do too, and large domains provide those [Lewis]
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Full Idea:
A consistent theory is, by definition, one satisfied by some model; an isomorphic image of a model satisfies the same theories as the original model; to provide the making of an isomorphic image of any given model, a domain need only be large enough.
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From:
David Lewis (Putnam's Paradox [1984], 'Why Model')
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A reaction:
This is laying out the ground for Putnam's model theory argument in favour of anti-realism. If you are chasing the one true model of reality, then formal model theory doesn't seem to offer much encouragement.
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14213
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Anti-realists see the world as imaginary, or lacking joints, or beyond reference, or beyond truth [Lewis]
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Full Idea:
Anti-realists say the only world is imaginary, or only has the parts or classes or relations we divide it into, or doubt that reference to the world is possible, or doubt that our interpretations can achieve truth.
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From:
David Lewis (Putnam's Paradox [1984], 'Why Anti-R')
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A reaction:
[compression of a paragraph on anti-realism] Lewis is a thoroughgoing realist. A nice example of the rhetorical device of ridiculing an opponent by suggesting that they don't even know what they themselves believe.
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14210
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A gerrymandered mereological sum can be a mess, but still have natural joints [Lewis]
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Full Idea:
The mereological sum of the coffee in my cup, the ink in this sentence, a nearby sparrow, and my left shoe is a miscellaneous mess of an object, yet its boundaries are by no means unrelated to the joints of nature.
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From:
David Lewis (Putnam's Paradox [1984], 'What Might')
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A reaction:
In that case they do, but if there are no atoms at the root of physics then presumably their could also be thoroughly jointless assemblages, involving probability distributions etc. Even random scattered atoms seem rather short of joints.
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14209
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Descriptive theories remain part of the theory of reference (with seven mild modifications) [Lewis]
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Full Idea:
Description theories of reference are supposed to have been well and truly refuted. I think not: ..it is still tenable with my seven points, and part of the truth of reference [7: rigidity, egocentric, tokens, causal, imperfect, indeterminate, families].
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From:
David Lewis (Putnam's Paradox [1984], 'Glob Desc')
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A reaction:
(The bit at the end refers to his seven points, on p.59). He calls his basic proposal 'causal descriptivism', incorporating his seven slight modifications of traditional descriptivism about reference.
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