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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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16756
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Substantial forms must exist, to explain the stability of metals like silver and tin [Albertus Magnus]
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Full Idea:
There is no reason why the matter in any natural thing should be stable in its nature, if it is not completed by a substantial form. But we see that silver is stable, and tin and other metals. Therefore they will seem to be perfected by substantial forms.
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From:
Albertus Magnus (On Minerals [1260], III.1.7), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 24.2
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A reaction:
Illuminating. This may be the best reason for proposing substantial forms. Once materialism arrives, the so-called 'laws' of nature have to be imposed on the material to do the job - but what the hell is a law supposed to be?
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