Full Idea
Never consider any objects but those capable of being defined in a finite number of word ...Avoid non-predicative classifications and definitions.
Gist of Idea
Avoid non-predicative classifications and definitions
Source
Henri Poincaré (The Logic of Infinity [1909], p.63), quoted by Penelope Maddy - Naturalism in Mathematics II.4
Book Reference
Maddy,Penelope: 'Naturalism in Mathematics' [OUP 2000], p.126