Full Idea
Anyone who wishes to avoid both bare identities and individual essences, without abandoning de re modality entirely, must adopt counterpart theory.
Clarification
De re modality concerns the possibilities in real things
Gist of Idea
De re modality without bare identities or individual essence needs counterparts
Source
Penelope Mackie (How Things Might Have Been [2006], 4.1)
Book Reference
Mackie,Penelope: 'How Things Might Have Been' [OUP 2006], p.71
A Reaction
This at least means that Lewis's proposal has an important place in the discussion, forcing us to think more clearly about the identities involved when we talk of possibilities. Mackie herself votes for bare indentities.