 One motivation for rejecting the appeal to  (EDR)  in the analysis of substance is that it permits two different entities to be existentially dependentR upon one another—entities such as Socrates and Socrates’s life. As we have seen,  (ID)  precludes any analogous symmetry where identity-dependence is concerned: indeed, it delivers the intuitively correct verdict that it is Socrates’s life that is, in this sense, ontologically dependent upon Socrates, rather than vice versa. For Socrates’s life is an extended event or process in which he participates—and which person Socrates is partially determines which event this is, but not vice versa. Or, to put it another way—one which should by now be familiar—it is part of the essence of Socrates’s life that it is the life of Socrates, but it is not part of the essence of Socrates that he is the person who lived that life. Of course, we can still acknowledge that the relation defined by  (EDR)  does hold mutually between Socrates and his life and we can still call this relationship a type of existential dependence—namely, “rigid” existential dependence. Similarly, we can recognize as other species of existential dependence the “generic” existential dependence defined by  (EDG),  the “asymmetrical” rigid existential dependence defined by  (EDA)  and the “essential” existential dependence defined by  (EDE).