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Single Idea 10045

[filed under theme 6. Mathematics / C. Sources of Mathematics / 10. Constructivism / d. Predicativism ]

Full Idea

Impredicative definitions are admitted into ordinary mathematics.

Gist of Idea

Impredicative definitions are admitted into ordinary mathematics

Source

Kurt Gödel (Russell's Mathematical Logic [1944], p.464)

Book Ref

'Philosophy of Mathematics: readings (2nd)', ed/tr. Benacerraf/Putnam [CUP 1983], p.464


A Reaction

The issue is at what point in building an account of the foundations of mathematics (if there be such, see Putnam) these impure definitions should be ruled out.


The 9 ideas from 'Russell's Mathematical Logic'

Impredicative Definitions refer to the totality to which the object itself belongs [Gödel]
In simple type theory the axiom of Separation is better than Reducibility [Gödel, by Linsky,B]
Mathematical Logic is a non-numerical branch of mathematics, and the supreme science [Gödel]
A logical system needs a syntactical survey of all possible expressions [Gödel]
Some arithmetical problems require assumptions which transcend arithmetic [Gödel]
Reference to a totality need not refer to a conjunction of all its elements [Gödel]
Mathematical objects are as essential as physical objects are for perception [Gödel]
Impredicative definitions are admitted into ordinary mathematics [Gödel]
The generalized Continuum Hypothesis asserts a discontinuity in cardinal numbers [Gödel]