Don Marquis’s “future-like-ours” argument against the moral permissibility of abortion is widely considered the strongest anti-abortion argument in the philosophical literature. In this paper, I address the issue of whether the argument relies upon controversial metaphysical premises. It is widely thought that future-like-ours argument indeed relies upon controversial metaphysics, in that it must reject the psychological theory of personal identity. I argue that that thought is mistaken—the future-like-ours argument does not depend upon the rejection of such a theory. I suggest, (...) however, that given a widely-accepted view about contraception and abstinence, the argument is committed to contentious metaphysics after all, as it relies upon a highly controversial assumption about mereology. This commitment is not only relevant for those who are inclined to endorse the argument but reject the mereological view in question, but in addition entails dialectical and epistemological liabilities for the argument, which on some views will be fatal to the argument’s overall success. (shrink)