Full Idea
Goodman argues that the set or class {{a}},{a,b}} is supposed to be distinct from the set or class {{b},{a,b}}, even though both are ultimately constituted from the same a and b.
Gist of Idea
Two objects can apparently make up quite distinct arrangements in sets
Source
report of Nelson Goodman (The Structure of Appearance [1951]) by JP Burgess / G Rosen - A Subject with No Object I.A.2.a
Book Reference
Burgess,J/Rosen,G: 'A Subject with No Object' [OUP 1997], p.27
A Reaction
I'm with Goodman all the way here, even though it is deeply unfashionable, particularly in the circles I move in. If there are trillion grains of sand on a beach, how many sets are we supposed to be committed to?