8954
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Geometrical circles cannot identify a circular paint patch, presumably because they lack something [Szabó]
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Full Idea:
The vocabulary of geometry is sufficient to identify the circle, but could not be used to identify any circular paint patch. The reason must be that the circle lacks certain properties that can distinguish paint patches from one another.
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From:
Zoltán Gendler Szabó (Nominalism [2003], 2.2)
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A reaction:
I take this to be support for the traditional view, that abstractions are created by omitting some of the properties of physical objects. I take them to be fictional creations, reified by language, and not actual hidden entities that have been observed.
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8955
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Abstractions are imperceptible, non-causal, and non-spatiotemporal (the third explaining the others) [Szabó]
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Full Idea:
In current discussions, abstract entities are usually distinguished as 1) in principle imperceptible, 2) incapable of causal interaction, 3) not located in space-time. The first is often explained by the second, which is in turn explained by the third.
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From:
Zoltán Gendler Szabó (Nominalism [2003], 2.2)
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A reaction:
Szabó concludes by offering 3 as the sole criterion of abstraction. As Lewis points out, the Way of Negation for defining abstracta doesn't tell us very much. Courage may be non-spatiotemporal, but what about Alexander the Great's courage?
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12709
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Motion is not absolute, but consists in relation [Leibniz]
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Full Idea:
In reality motion is not something absolute, but consists in relation.
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From:
Gottfried Leibniz (On Motion [1677], A6.4.1968), quoted by Daniel Garber - Leibniz:Body,Substance,Monad 3
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A reaction:
It is often thought that motion being relative was invented by Einstein, but Leibniz wholeheartedly embraced 'Galilean relativity', and refused to even consider any absolute concept of motion. Acceleration is a bit trickier than velocity.
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