Abstract
I argue that the personhood of a fetus is analogous to the the heap. If this is correct, then the moral status or intrinsic value of a fetus would be supervenient upon the fetus's biological development. Yet to compare its claim vis-a-vis its mother's, we need to consider not only their moral status, but also the type of claim they each have. Thus we have to give weight to the two factors or variables of the mother's moral status and her claim to some lesser good . And then we have to consider the fetus's lesser moral status and its claim to some greater good, namely, life. I argue that we do not know how to compare these two-variable claims. This also explains why the central cases of abortion have been so difficult to resolve. I suggest that the problem of animal rights has a similar structure