Full Idea
We can address a set with any question at all that admits of a numerical reply. Thus we can ask of {Carter, Reagan} 'How many feet do the members have?'.
Gist of Idea
You can ask all sorts of numerical questions about any one given set
Source
Palle Yourgrau (Sets, Aggregates and Numbers [1985], 'On Numbering')
Book Reference
'Philosophy of Mathematics: anthology', ed/tr. Jacquette,Dale [Blackwell 2002], p.358
A Reaction
This is his objection to the Fregean idea that once you have fixed the members of a set, you have thereby fixed the unique number that belongs with the set.
Related Ideas
Idea 17819 A set doesn't have a fixed number, because the elements can be seen in different ways [Yourgrau on Frege]
Idea 17820 If you can subdivide objects many ways for counting, you can do that to set-elements too [Yourgrau on Frege]