Full Idea
Classes, so far as we introduce them, are merely symbolic or linguistic conveniences, not genuine objects.
Gist of Idea
We regard classes as mere symbolic or linguistic conveniences
Source
B Russell/AN Whitehead (Principia Mathematica [1913], p.72), quoted by Penelope Maddy - Naturalism in Mathematics III.2
Book Reference
Maddy,Penelope: 'Naturalism in Mathematics' [OUP 2000], p.172