Full Idea
Classes may be regarded as logical fictions, manufactured out of defining characteristics.
Gist of Idea
Classes are logical fictions, made from defining characteristics
Source
Bertrand Russell (Introduction to Mathematical Philosophy [1919], II n1)
Book Reference
Russell,Bertrand: 'Introduction to Mathematical Philosophy' [George Allen and Unwin 1975], p.14
A Reaction
I agree with this. The idea that in addition to the members there is a further object, the set containing them, is absurd. Sets are a tool for thinking about the world.