Full Idea
The contention of the 'no classes' theory is that all significant propositions concerning classes can be regarded as propositions about all or some of their members.
Gist of Idea
The 'no classes' theory says the propositions just refer to the members
Source
Bertrand Russell (On 'Insolubilia' and their solution [1906], p.200)
Book Reference
Russell,Bertrand: 'Essays in Analysis', ed/tr. Lackey,Douglas [George Braziller 1973], p.200
A Reaction
Apparently this theory has not found favour with later generations of theorists. I see it in terms of Russell trying to get ontology down to the minimum, in the spirit of Goodman and Quine.