9987
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An aggregate in which order does not matter I call a 'set' [Bolzano]
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Full Idea:
An aggregate whose basic conception renders the arrangement of its members a matter of indifference, and whose permutation therefore produces no essential difference, I call a 'set'.
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From:
Bernard Bolzano (Paradoxes of the Infinite [1846], §4), quoted by William W. Tait - Frege versus Cantor and Dedekind IX
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A reaction:
The idea of 'sets' was emerging before Cantor formalised it, and clarified it by thinking about infinite sets. Nowadays we also have 'ordered' sets, which rather contradicts Bolzano, and we also expect the cardinality to be determinate.
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16689
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The schools said spirits lack extension, and wonder how many could dance on a needle's point [More,H]
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Full Idea:
Many, not without reason, laugh at those ridiculous fancies of the schools, that rashly take away all extensions from spirits, whether souls or angels, and then dispute how many of them booted and spurred may dance on a needle's point at once.
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From:
Henry More (Immortality of the Soul [1659], III.2.1), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 17.3
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A reaction:
This famous idea originated with William Chillingworth. More's version is the classic one. Pasnau cites Aquinas Summa 1a 52.3 as discussing the actual question (and says this couldn't happen).
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