Full Idea
While Socrates has no counterparts that lack self-identity, he does have counterparts that lack identity-with-Socrates. He alone has that - the property, that is, of being identical with the object that in fact instantiates Socrateity.
Gist of Idea
The counterparts of Socrates have self-identity, but only the actual Socrates has identity-with-Socrates
Source
Alvin Plantinga (Transworld Identity or worldbound Individuals? [1973], II)
Book Reference
'The Possible and the Actual', ed/tr. Loux,Michael J. [Cornell 1979], p.162
A Reaction
I am never persuaded by arguments which rest on such dubious pseudo-properties. Whether or not a counterpart of Socrates has any sort of identity with Socrates cannot be prejudged, as it would beg the question.