18801
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Classical negation is circular, if it relies on knowing negation-conditions from truth-conditions [Dummett]
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Full Idea:
Explanations of classical negation assume that knowing what it is for the truth-condition of some statement to obtain, independently of recognising it to obtain, we thereby know what it is for it NOT to obtain; but this presupposes classical negation.
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From:
Michael Dummett (The Logical Basis of Metaphysics [1991], p.299), quoted by Ian Rumfitt - The Boundary Stones of Thought 1.1
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A reaction:
[compressed wording] This is Dummett explaining why he prefers intuitionistic logic, with its doubts about double negation.
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9212
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Possible states of affairs are not propositions; a proposition can't be a state of affairs! [Fine,K]
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Full Idea:
Possible states of affairs have often been taken to be propositions, but this cannot be correct, since any possible state of affairs is possibly a state of affairs, but no proposition is possibly a state of affairs.
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From:
Kit Fine (The Problem of Possibilia [2003], 2)
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A reaction:
The point is, presumably, that the state of affairs cannot be the proposition itself, but (at least) what the proposition refers to. I can't see any objection to that.
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9213
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The actual world is a possible world, so we can't define possible worlds as 'what might have been' [Fine,K]
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Full Idea:
A possible world can't be defined (by Stalnaker and Plantinga) as a way the world might have been, because a possible world is possibly the world, yet no way the world might have been is possibly the world.
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From:
Kit Fine (The Problem of Possibilia [2003], 2)
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A reaction:
His point is that any definition of a possible world must cover the actual world, because that is one of them. 'Might have been' is not applicable to the actual world. It seems a fairly important starting point for discussion of possible worlds.
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11214
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We learn 'not' along with affirmation, by learning to either affirm or deny a sentence [Rumfitt]
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Full Idea:
The standard view is that affirming not-A is more complex than affirming the atomic sentence A itself, with the latter determining its sense. But we could learn 'not' directly, by learning at once how to either affirm A or reject A.
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From:
Ian Rumfitt ("Yes" and "No" [2000], IV)
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A reaction:
[compressed] This seems fairly anti-Fregean in spirit, because it looks at the psychology of how we learn 'not' as a way of clarifying what we mean by it, rather than just looking at its logical behaviour (and thus giving it a secondary role).
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