Full Idea
Weak Limitation of Size: If there are no more Fs than Gs and the Gs form a collection, then Fs form a collection. Strong Limitation of Size: A property F fails to be collectivising iff there are as many Fs as there are objects.
Gist of Idea
Limitation of Size is weak (Fs only collect is something the same size does) or strong (fewer Fs than objects)
Source
report of George Boolos (Iteration Again [1989]) by Michael Potter - Set Theory and Its Philosophy 13.5
Book Reference
Potter,Michael: 'Set Theory and Its Philosophy' [OUP 2004], p.227