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9390
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Logic guides thinking, but it isn't a substitute for it [Rumfitt]
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Full Idea:
Logic is part of a normative theory of thinking, not a substitute for thinking.
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From:
Ian Rumfitt (The Logic of Boundaryless Concepts [2007], p.13)
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A reaction:
There is some sort of logicians' dream, going back to Leibniz, of a reasoning engine, which accepts propositions and outputs inferences. I agree with this idea. People who excel at logic are often, it seems to me, modest at philosophy.
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9389
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Vague membership of sets is possible if the set is defined by its concept, not its members [Rumfitt]
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Full Idea:
Vagueness in respect of membership is consistency with determinacy of the set's identity, so long as a set's identity is taken to consist, not in its having such-and-such members, but in its being the extension of a concept.
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From:
Ian Rumfitt (The Logic of Boundaryless Concepts [2007], p.5)
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A reaction:
I find this view of sets much more appealing than the one that identifies a set with its members. The empty set is less of a problem, as well as non-existents. Logicians prefer the extensional view because it is tidy.
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7634
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Icons resemble their subject, an index is a natural sign, and symbols are conventional [Peirce, by Maund]
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Full Idea:
For Peirce there are three different kinds of sign, which are different kinds of representation, built on different relationships: an 'icon' represents what it resembles, an 'index' is a natural sign, and a 'symbol' is a conventional sign.
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From:
report of Charles Sanders Peirce (Logic as Semiotic: Theory of Signs [1897]) by Barry Maund - Perception Ch.4
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A reaction:
Maund makes use of natural signs (like footprints) to explain representative perception. Peirce's distinctions seem useful in philosophy of mind generally, if the brain somehow represents what it experiences. How subjective are signs?
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