In Don Marquis’ article Why Abortion is Immoral, he makes the argument that abortion is on the same plane of immorality as killing an adult human. Marquis reasons this by explaining what is wrong with killing is that you are depriving someone of a future. He goes on to explain that you deprive them of a future of experiences, achievements, relationships, etc. Importantly, he notes that this does not only apply to humans but rather to all species, or anything with a future of value for that matter. Furthermore, Marquis says that having a valuable future is not a necessary condition for killing to be immoral, but it is a sufficient reason, and that having a valuable future is not the only reason that killing a being could be wrong. Essentially, Marquis offers one explanation as to why killing could be immoral while clarifying that it could be one of many reasons for killing to be immoral.
Marquis then connects this idea with abortion by saying that aborting a fetus is depriving a being of a valuable future. Regardless of what pro-choice or pro-life views somebody might have, the bottom line is that the fetus has the potential for a valuable future and
References: Marquis, Don. “Why Abortion Is Immoral.” N.p., 1989. Web. 08 May 2014. <https://myelms.umd.edu/courses/1056989/files/32707184?module_item_id=7195906>. Warren, Mary Anne. “On the Moral and Legal Status of Abortion.” N.p., 1973. Web. 08 May 2014. <https://myelms.umd.edu/courses/1056989/files/31386874?module_item_id=7083927>.