Full Idea
To get units by abstraction, units arrived at by abstraction from forks must the identical to that abstracted from spoons, with no trace of individuality. But if spoons can no longer be differentiated from forks, they can't differ from one another either.
Gist of Idea
To abstract from spoons (to get the same number as the forks), the spoons must be indistinguishable too
Source
Michael Dummett (Frege philosophy of mathematics [1991], Ch. 8)
Book Reference
Dummett,Michael: 'Frege: philosophy of mathematics' [Duckworth 1991], p.86
A Reaction
[compressed] Dummett makes the point better than Frege did. Can we 'think of a fork insofar as it is countable, ignoring its other features'? What are we left thinking of? Frege says it must still be the whole fork. 'Nice fork, apart from the colour'.