Transworld

But it doesn't really come to the same thing, because the usual notion of a criterion of transworld identity demands that we give purely qualitative necessary and sufficient conditions for someone being Nixon.

If we start with transworld individuals which exist in several possible worlds, we can, as Lewis pointed out, construct world-specific individuals as ordered pairs, of which the first member is a transworld individual and the second member is a possible world ...

Although this approach avoids the problem of specifying transworld identity relations, it provokes another objection concerning the essential properties that must be attributed to any individual in a world in which the individual exists.