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Single Idea 17828

[filed under theme 6. Mathematics / B. Foundations for Mathematics / 6. Mathematics as Set Theory / a. Mathematics is set theory ]

Full Idea

I propose that ...numbers are properties of sets, analogous, for example, to lengths, which are properties of physical objects.

Gist of Idea

Numbers are properties of sets, just as lengths are properties of physical objects

Source

Penelope Maddy (Sets and Numbers [1981], III)

Book Ref

'Philosophy of Mathematics: anthology', ed/tr. Jacquette,Dale [Blackwell 2002], p.349


A Reaction

Are lengths properties of physical objects? A hole in the ground can have a length. A gap can have a length. Pure space seems to contain lengths. A set seems much more abstract than its members.


The 8 ideas from 'Sets and Numbers'

If mathematical objects exist, how can we know them, and which objects are they? [Maddy]
The master science is physical objects divided into sets [Maddy]
Set theory (unlike the Peano postulates) can explain why multiplication is commutative [Maddy]
Standardly, numbers are said to be sets, which is neat ontology and epistemology [Maddy]
Numbers are properties of sets, just as lengths are properties of physical objects [Maddy]
Sets exist where their elements are, but numbers are more like universals [Maddy]
Number words are unusual as adjectives; we don't say 'is five', and numbers always come first [Maddy]
Number theory doesn't 'reduce' to set theory, because sets have number properties [Maddy]