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Single Idea 10553

[filed under theme 6. Mathematics / B. Foundations for Mathematics / 5. Definitions of Number / c. Fregean numbers ]

Full Idea

For Frege, in 'Grundgesetze', a number is a class of classes of the same cardinality.

Gist of Idea

A number is a class of classes of the same cardinality

Source

report of Gottlob Frege (Grundgesetze der Arithmetik 2 (Basic Laws) [1903]) by Michael Dummett - Frege Philosophy of Language (2nd ed) Ch.14

Book Ref

Dummett,Michael: 'Frege Philosophy of Language' [Duckworth 1981], p.510


The 12 ideas from 'Grundgesetze der Arithmetik 2 (Basic Laws)'

Later Frege held that definitions must fix a function's value for every possible argument [Frege, by Wright,C]
Real numbers are ratios of quantities [Frege, by Dummett]
A number is a class of classes of the same cardinality [Frege, by Dummett]
Frege's biggest error is in not accounting for the senses of number terms [Hodes on Frege]
Cardinals say how many, and reals give measurements compared to a unit quantity [Frege]
The modern account of real numbers detaches a ratio from its geometrical origins [Frege]
The first demand of logic is of a sharp boundary [Frege]
Only what is logically complex can be defined; what is simple must be pointed to [Frege]
We can't define a word by defining an expression containing it, as the remaining parts are a problem [Frege]
Formalism misunderstands applications, metatheory, and infinity [Frege, by Dummett]
Only applicability raises arithmetic from a game to a science [Frege]
If we abstract the difference between two houses, they don't become the same house [Frege]