 Essential Properties.   It follows from the  unrestricted nature of recombination that, for any simple object  a and simple universal P, a recombines with  P in some worlds and fails to recombine with P in  others. Generalizing from this fact, it follows that no simple or sum of simples has any simple universal or conjunction of simple  universals essentially. It also follows that no such object has any  structural property essentially. For assume o is such an  object and that it exemplifies a structural property P. Since  P is structural, it supervenes on some set of simple states of affairs. But by the nature of recombination, there are combinatorial  worlds in which those states of affairs do not exist and, hence, in  which P doesn't but o — being a simple or a sum  of simples — does. 