In my previous article, I examined the argument against abortion that I consider to be the strongest, the Substance View. This argument, by philosopher Don Marquis, is also a very strong argument and, when used in tandem with the Substance View, offers a very powerful cumulative case against abortion.
This argument comes from Marquis’ 1989 article Why Abortion is Immoral. According to pro-choice philosopher David Boonin, this Marquis’ article is “widely viewed by philosophers as containing the single most powerful argument against abortion.” (David Boonin, A Defense of Abortion, Cambridge University Press, Cambridge, New York, 2003, p. 20.) All future citations in this article are from Marquis’ article Why Abortion is Immoral.
Marquis begins by examining several pro-life and pro-choice arguments, and concluding that they’re generally at a stand-still. For example, take the following two paragraphs:
“Consider the way a typical antiabortionist argues. She will argue or assert that life is present from the moment of conception or that fetuses look like babies or that fetuses possess a characteristic such as a genetic code that is both necessary or sufficient for being human. Antiabortionists seem to believe that (1) the truth of any of these claims is quite obvious, and (2) establishing any of these claims is sufficient to show that an abortion is morally akin to murder.
“A standard pro-choice strategy exhibits similarities. The pro-choicer will argue or assert that fetuses are not persons or that fetuses are not rational agents or that fetuses are not social beings. Pro-choicers seem to believe that (1) the truth of any of these claims is quite obvious, and (2) establishing any of these claims is sufficient to show that abortion is not a wrong killing.”
He examines several more of these apparent symmetries in the abortion issue. Believing himself to have found the deciding factor in the abortion debate, he begins from a premise that is uncontroversial. It is wrong to kill us (that is, you and me). Why is it wrong to kill us? Marquis provides a discussion of the reason:
“Some answers can be eliminated. It might be said that what makes killing us wrong is that a killing brutalizes the one who kills. But the brutalization consists of being injured to the performance of an act that is hideously immoral; hence, the brutalization does not explain the immorality. It might be said that what makes killing us wrong is the great loss others would experience due to our absence. Although such hubris is understandable, such an explanation does not account for the wrongness of killing hermits, or those whose lives are relatively independent and whose friends find it easy to make new friends.
“A more obvious answer is better. What primarily makes killing wrong is neither its effect on the murderer nor its effect on the victim’s friends and relatives, but its effect on the victim. The loss of one’s life is one of the greatest losses one can suffer. The loss of one’s life deprives one of all the experiences, activities, projects and enjoyments that would otherwise have constituted one’s future. Therefore, killing someone is wrong, primarily because the killing inflicts (one of) the greatest possible losses on the victim.”
What makes killing any of us wrong is not simply the fact that our life is taken against our will (as this wouldn’t explain why it is wrong to kill suicidal people). What makes killing us wrong is that we are robbed of all of the experiences, activities, etc. that we would have experienced had we been allowed to continue living. It is also uncontroversial that killing children is wrong, for the same reason. Some may believe that infanticide is morally permissible, but if this account of the wrongness of killing is correct, then that also makes infanticide morally wrong. Incidentally, this also accounts for why abortion is seriously wrong. The embryo/fetus also has a “Future Like Ours,” that is, a future with similar experiences, activities, projects, and enjoyments that they will come to experience.
Marquis also mentions that having a “future like ours” is a sufficient condition, not a necessary one to account for the wrongness of killing. As he writes, “Some persons in nursing homes may lack valuable human futures, yet it may be wrong to kill them for other reasons. Furthermore, this account does not obviously have to be the sole reason killing is wrong where the victim did have a valuable future. This analysis claims only that, having that future by itself is sufficient to create the strong presumption that the killing is seriously wrong.”
An objection I commonly hear to this argument is that it would mean that contraception is immoral, since sperm and ova also have a “future-like-ours.” But this rests on a common pro-choice strawman of the pro-life position. We argue that the human zygote is valuable because it is a living human organism, a member of species Homo sapiens. Sperm and eggs are mere haploid cells, from the larger parent organism (the man or woman who provided it). The sperm and eggs are not human organisms. As such, they do not have a “future like ours,” that is, a future of experiences, plans, etc., that all human beings will experience. Their future is to provide genetic information for the new human organism, then to die as soon as they contribute their genetic material. 
Additionally, Marquis addresses this in his article. He writes, “...this analysis does not entail that contraception is wrong. Of course, contraception prevents the actualization of a possible future of value. Hence, it follows from the claim that futures of value should be maximized that contraception is prima facie immoral. This obligation to maximize does not exist, however; furthermore, nothing in the ethics of killing in this paper entails that it does. The ethics of killing in this essay would entail that contraception is wrong only if something were denied a human future of value by contraception. Nothing at all is denied such a future by contraception however.”
Marquis’ Future-Like-Ours argument, coupled with Beckwith’s Substance View, creates a very powerful cumulative case as to why abortion is a serious moral wrong. I have yet to see a pro-choice advocate convincingly argue against either of these two positions.
 I owe this observation to my friend and pro-life advocate Josh Brahm.