 Note that defining intrinsic properties as those that do not divide duplicates is hopeless unless it is combined with something like Lewis’s modal realism. Being a dog-owner is not intrinsic; but unless there are vast numbers of people, it is unlikely that any dog-owner is a duplicate of a non-dog-owner. It will not help to define the intrinsic properties as those that could not divide duplicates, since being a duplicate of a dog-owner is also not intrinsic. A better idea is to replace the binary relation of duplication with a four-place relation between two objects and two possible worlds, in which case we can say that property \(F\) is intrinsic if and only if, whenever \(x\) as it is at \(w\) is a duplicate of \(y\) as it is at \(w'\), \(x\) has \(F\) at \(w\) just in case \(y\) has \(F\) at \(w'\).  Duplication  can be modified to turn it into an analysis of this four-place relation: