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Single Idea 9906
[filed under theme 6. Mathematics / B. Foundations for Mathematics / 6. Mathematics as Set Theory / b. Mathematics is not set theory
]
Full Idea
If a particular set-theory is in a strong sense 'reducible to' the theory of ordinal numbers... then we can still ask, but which is really which?
Gist of Idea
If ordinal numbers are 'reducible to' some set-theory, then which is which?
Source
Paul Benacerraf (What Numbers Could Not Be [1965], IIIB)
Book Ref
'Philosophy of Mathematics: readings (2nd)', ed/tr. Benacerraf/Putnam [CUP 1983], p.290
A Reaction
A nice question about all reductions. If we reduce mind to brain, does that mean that brain is really just mind. To have a direction (up/down?), reduction must lead to explanation in a single direction only. Do numbers explain sets?
Related Idea
Idea 10687
Maybe we reduce sets to ordinals, rather than the other way round [Hossack]
The
24 ideas
from 'What Numbers Could Not Be'
9151
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Benacerraf says numbers are defined by their natural ordering
[Benacerraf, by Fine,K]
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13891
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To understand finite cardinals, it is necessary and sufficient to understand progressions
[Benacerraf, by Wright,C]
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8697
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Disputes about mathematical objects seem irrelevant, and mathematicians cannot resolve them
[Benacerraf, by Friend]
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8304
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No particular pair of sets can tell us what 'two' is, just by one-to-one correlation
[Benacerraf, by Lowe]
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17904
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A set has k members if it one-one corresponds with the numbers less than or equal to k
[Benacerraf]
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9898
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We can count intransitively (reciting numbers) without understanding transitive counting of items
[Benacerraf]
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17903
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Someone can recite numbers but not know how to count things; but not vice versa
[Benacerraf]
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9897
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The application of a system of numbers is counting and measurement
[Benacerraf]
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17906
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To explain numbers you must also explain cardinality, the counting of things
[Benacerraf]
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9900
|
For Zermelo 3 belongs to 17, but for Von Neumann it does not
[Benacerraf]
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9899
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The successor of x is either x and all its members, or just the unit set of x
[Benacerraf]
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9901
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Numbers can't be sets if there is no agreement on which sets they are
[Benacerraf]
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9903
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Number words are not predicates, as they function very differently from adjectives
[Benacerraf]
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9904
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The set-theory paradoxes mean that 17 can't be the class of all classes with 17 members
[Benacerraf]
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9905
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Identity statements make sense only if there are possible individuating conditions
[Benacerraf]
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9906
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If ordinal numbers are 'reducible to' some set-theory, then which is which?
[Benacerraf]
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9907
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If any recursive sequence will explain ordinals, then it seems to be the structure which matters
[Benacerraf]
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9908
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The job is done by the whole system of numbers, so numbers are not objects
[Benacerraf]
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9909
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The number 3 defines the role of being third in a progression
[Benacerraf]
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9911
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Number words no more have referents than do the parts of a ruler
[Benacerraf]
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9910
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Number-as-objects works wholesale, but fails utterly object by object
[Benacerraf]
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9912
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There are no such things as numbers
[Benacerraf]
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8925
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Mathematical objects only have properties relating them to other 'elements' of the same structure
[Benacerraf]
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9938
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How can numbers be objects if order is their only property?
[Benacerraf, by Putnam]
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