Don Marquis, a professor of philosophy at the University of Kansas, is the author of "Why Abortion Is Immoral" (Journal of Philosophy, Vol. 86, No. 4 (Apr., 1989), pp. 183-202). The full text of Marquis's paper seems to be unavailable on the web, except for a fee (here).
This post gives a thumbnail version of Marquis's argument, based on an interview of Marquis by Hugh LaFollette, host of the (defunct) program Ideas and Issues at WETS-FM. The interview, which lasts about 25 minutes, was broadcast on February 8, 1997. Here's a synopsis:
To understand what's wrong with abortion, start by asking what's wrong with murder. It is depriving a person of a future of value, if a person has such a future. That is the best explanation of why we think it's wrong to kill except in exigent circumstances. For example, it would be merciful to kill a person who is trapped in a burning car and dying in agony. (Presumably, killing murderers in the service of justice and enemies self-defense are similarly defensible because such acts protect lives of value.)
Given the wrongness of killing (in most circumstances), it's wrong to kill an infant because it deprives the infant of its future of value. Similarly, it's wrong to kill a fetus, for the same reason.
What about the objection that an adult has interests but a fetus does not? A fetus is an undeveloped human being that will have interests.
What about the objection that an adult is conscious and aware, whereas a fetus in early stages of development is not. The fetus will be conscious and aware, just as a person in a termporary coma will be conscious and aware. If killing the person in a coma is wrong, killing an early-stage fetus is wrong for the same reason.
What about contraception? Contraception does not end the life of a definite individual with a future. There is an individual after conception, but not before.
What about the status of the mother who is carrying a fetus. Isn't her life worth consideration? Shouldn't she have a choice? Liberty always is constrained by moral considerations. In this instance, it is right to restrict the liberty to abort, because abortion is wrong.
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