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 Reference
'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.