  References to identity in this debate come from objectors to this argument, who apply the argument from fission to a real life version of it, namely, twinning. An embryo might split any time generally before the two-week point in fetal development, and those two embryos could develop into fully formed infant twins. The question for the advocate of the above argument to consider is, in such a case, what happens to the original human being, the embryo we will call Adam? There are only three possibilities: (a) either Adam survives as both twins, (b) Adam survives only as one or the other of the twins, or (c) Adam does not survive. Option (a) cannot be right, given that the twins will live distinct, individual lives, and so will clearly be two human beings, not one. Option (b) cannot be right, for what non-arbitrary reason could there be for one of the twins to be Adam and not the other? They will both be qualitatively identical to Adam, after all. The only remaining option, then, is (c), in which Adam does not survive. But this has two bad implications for the above advocate. First, if it is a tragedy when a human being dies, then twinning involves a tragedy, and Adam's death, it seems, ought to be mourned. This seems absurd (McMahan 1995 and 2002, 26; although see Oderberg 1997 for an embrace of this implication).  Second, if the metaphysical analysis is right, then Adam's death brings about the existence of two new human beings (call them Barney and Claire). But this means that (1) it is not the case that all human beings come into existence at conception (some  come into existence at twinning), and (2) death can somehow occur  with no earthly remains, which is at best odd and at worst false  (Kuhse and Singer 2002, 190).