Full Idea
If we come to regard an 'idea' like whiteness as an act of thought, then we come to think of whiteness as mental, but in doing so we rob it of its essential quality of universality.
Gist of Idea
If we consider whiteness to be merely a mental 'idea', we rob it of its universality
Source
Bertrand Russell (Problems of Philosophy [1912], Ch. 9)
Book Reference
Russell,Bertrand: 'The Problems of Philosophy' [OUP 1995], p.57
A Reaction
Presumably we need an ontological commitment to the existence of universals, which is very Platonic. Fatherhood might be a better example, since whiteness is a quale.