Full Idea
Lewis takes the counterpart relation to be sortal-relative, so he (no less than Quine) denies that objects, qua existing, are necessarily a certain way.
Clarification
'qua' means insofar as
Gist of Idea
The counterpart relation is sortal-relative, so objects need not be a certain way
Source
report of David Lewis (On the Plurality of Worlds [1986]) by Trenton Merricks - Truth and Ontology 5.III n10
Book Reference
Merricks,Trenton: 'Truth and Ontology' [OUP 2007], p.112
A Reaction
Does this mean that there could be two different versions of the same possible world (certainly not!), or that worlds are entirely created by our concepts rather than by what is actually possible.