Worldbound

Since every concrete individual or thing is worldbound, I could not have had properties other than those I in fact have

What we should do here is not to set up a contrast between worldbound individuals and world lines, but to recognize that world lines are an indispensable means of speaking and thinking of the usual perfectly ordinary-looking entities, the ordinary denizens of the actual world.

Lewis accepts that both these objects exist: his mereological universalism (belief in arbitrary sums) guarantees the existence of the transworld object, given the existence of the various worldbound objects.