  Call superessentialism the doctrine that for any individual substance, x, and for any property P of x, necessarily, if x exists, then x has P.  In other words, every property is essential to x.  For example, one might imagine that crosser of the Rubicon or possessor of 12,147 hairs on his head on the Ides of March, 44 B.C.E. were properties that, were they different, the Caesar of our world would no longer exist. (For the sake of argument, assume that the head-hair count is true; it is only supposed to get at some seemingly trivial property.) Or, put differently, if those properties were different, the Caesars would be genuinely different individual substances.