Full Idea
The view that properties exist, but are particulars rather than universals, is still left with the problem of classification. On what basis do we declare that different things have the same property?
Gist of Idea
If properties and relations are particulars, there is still the problem of how to classify and group them
Source
David M. Armstrong (Universals [1995], p.504)
Book Reference
'A Companion to Metaphysics', ed/tr. Kim,Jaegwon/Sosa,Ernest [Blackwell 1995], p.504
A Reaction
This seems like a fairly crucial objection. The original problem was how we manage to classify things (group them into sets), and it looks as if this theory leaves the problem untouched.