14182
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If the logic of 'taller of' rests just on meaning, then logic may be the study of merely formal consequence [Read]
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Full Idea:
In 'A is taller than B, and B is taller than C, so A is taller than C' this can been seen as a matter of meaning - it is part of the meaning of 'taller' that it is transitive, but not of logic. Logic is now seen as the study of formal consequence.
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From:
Stephen Read (Formal and Material Consequence [1994], 'Reduct')
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A reaction:
I think I find this approach quite appealing. Obviously you can reason about taller-than relations, by putting the concepts together like jigsaw pieces, but I tend to think of logic as something which is necessarily implementable on a machine.
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14184
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In modus ponens the 'if-then' premise contributes nothing if the conclusion follows anyway [Read]
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Full Idea:
A puzzle about modus ponens is that the major premise is either false or unnecessary: A, If A then B / so B. If the major premise is true, then B follows from A, so the major premise is redundant. So it is false or not needed, and contributes nothing.
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From:
Stephen Read (Formal and Material Consequence [1994], 'Repres')
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A reaction:
Not sure which is the 'major premise' here, but it seems to be saying that the 'if A then B' is redundant. If I say 'it's raining so the grass is wet', it seems pointless to slip in the middle the remark that rain implies wet grass. Good point.
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14186
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Logical connectives contain no information, but just record combination relations between facts [Read]
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Full Idea:
The logical connectives are useful for bundling information, that B follows from A, or that one of A or B is true. ..They import no information of their own, but serve to record combinations of other facts.
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From:
Stephen Read (Formal and Material Consequence [1994], 'Repres')
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A reaction:
Anyone who suggests a link between logic and 'facts' gets my vote, so this sounds a promising idea. However, logical truths have a high degree of generality, which seems somehow above the 'facts'.
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14742
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It can't be indeterminate whether x and y are identical; if x,y is indeterminate, then it isn't x,x [Salmon,N]
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Full Idea:
Insofar as identity seems vague, it is provably mistaken. If it is vague whether x and y are identical (as in the Ship of Theseus), then x,y is definitely not the same as x,x, since the first pair is indeterminate and the second pair isn't.
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From:
Nathan Salmon (Reference and Essence: seven appendices [2005], App I)
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A reaction:
[compressed; Gareth Evans 1978 made a similar point] This strikes me as begging the question in the Ship case, since we are shoehorning the new ship into either the slot for x or the slot for y, but that was what we couldn’t decide. No rough identity?
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