The aim of this article is to understand the apparent impasse in the problem of abortion. I admit that the particular circumstance in which an abortion is sought is morally relevant. Thus, if an abortion is sought because the mother’s life is endangered, or the fetus is grossly deformed, or the pregnancy was the result of rape, then abortion is morally justified, regardless of whether a fetus is a person or not. Notwithstanding these cases, whether a fetus is a person is morally vital for answering the question of whether abortion is justified in most other cases. I assume that whether a fetus is a person is analogous to the question of whether certain grains of sand can form a heap, in that the concepts of person and heap are both vague. I then argue that just as the degree of heapness supervenes on the number of grains, so the degree of personhood supervenes on the biological development of a fetus. I further argue that the intrinsic value, or moral status, of a fetus is a function of its degree of personhood.
However, to resolve the problem of abortion in a “usual” case, we typically have to resolve the conflict of the mother’s claim to freedom and the fetus’s claim to life. That is, we have to take account of (1) the mother’s higher moral status as a person and the fetus’s lower moral status as having only a certain degree of personhood on the one hand, and of (2) the mother’s less weighty claim to freedom and the fetus’s weightier claim to life on the other hand, and then somehow compare the two claims. Yet we do not know how to combine “moral status” and “type of claim” into a single claim, as we do not have any ethical calculus or conceptual apparatus for doing so, or for comparing the lesser claim of a greater being (e.g., a mother’s freedom) and the greater claim of a lesser being (e.g., a fetus’s life). Hence, a mother’s claim to freedom and a fetus’s claim to life seem incommensurable. The same is true of a person’s claim to tasting a steak and a cow’s claim to life, for we do not know how to combine a cow’s lesser moral status (compared with the person’s higher moral status) and its more important claim to life (compared with the person’s claim to gastronomic pleasure) into a single claim, or compare it with the person’s claim to gastronomic pleasure (which has to take account of the person’s higher moral status and less weighty claim). Because these competing claims seem incommensurable, the problems of abortion and animal rights are irresolvable. At least, the difficulties of these problems have a deeper source than we have so far acknowledged.
本文旨在了解墮胎問題為甚麼那麼難解決。除了一些特殊的情況之外（例如母親如果不墮胎，性命將受威脅），究竟胎兒是不是人這個問題是解決墮胎問題的重要關鍵。我假設胎兒是不是人這問題，是跟多少粒沙便可成堆這個問題相類似，因為兩者都牽涉模糊性。然後我論證：正如沙的成堆度 (degree of heapness)取決於沙粒的多寡，那麼胎兒的成人度 (degree of personhood) 亦取決於胎兒生理上的發展。我進一步論證胎兒的內在價值或道德地位，是取決於它的成人度。問題是，我們不懂得如何去比較母親對自由的索求和胎兒對生命的索求，因為我們不懂得如何將道德地位和索求的種類合併：我們既沒有任何倫理演算法或概念上的工具，可用來衡量一個重要生物的較輕微索求（例如母親的自由），和一個較輕微生物的重要索求（例如胎兒的生命）。同樣地，在道德素食主義的問題上，我們不知道怎樣去衡量或比較一頭牛對生命的索求，和一個食家對味道的索求。因為這兩類索求不但是互相競爭，而且是不相稱的，因此墮胎和道德素食主義這兩個難題，是不能被解決的。起碼，它們的疑難，有一個我們還未探索的源頭。