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15927
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Definition just needs negation, known variables, conjunction, disjunction, substitution and quantification [Weyl, by Lavine]
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Full Idea:
For mathematics, Weyl arrived (by 1917) at a satisfactory list of definition principles: negation, identification of variables, conjunction, disjunction, substitution of constants, and existential quantification over the domain.
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From:
report of Hermann Weyl (works [1917]) by Shaughan Lavine - Understanding the Infinite V.3
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A reaction:
Lavine summarises this as 'first-order logic with parameters'.
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6493
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We are not conscious of pure liquidity, but of the liquidity of water [Firth]
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Full Idea:
We are not conscious of liquidity, coldness, and solidity, but of the liquidity of water, the coldness of ice, and the solidity of rocks.
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From:
Roderick Firth (Sense Data and the Percept Theory [1949]), quoted by Howard Robinson - Perception 1.7
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A reaction:
A nice point, but it might not be entirely true in a blindfold test, where one might only report properties like 'sticky' or 'warm', without having any clear concept of the substance being experienced. Firth is proposing the 'percept theory'.
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