One potential problem with the argument Marquis gives is that it might seem to rule out contraception: in preventing the conception of a being, one is cutting off a possible future. The essence of Marquis' reply is that contraception is different from abortion: in the case of contraception there is no particular being whose future is being cut off. He reasons as follows: there are four potential candidate "beings":
- the sperm cell
- the ovum
- the sperm-ovum pair considered separately
- the sperm-ovum combination
Neither 1) not 2) is satisfactory. A sperm alone does not determine a being. Neither does an ovum. 3) counts too many beings. This sounds a bit odd, but in fact, we can strengthen point here. On any given occasion of intercourse, there are typically millions of sperm. There is no one of them in particular that should be counted as the one whose future is being cut off. And this ties in with Marquis's point about 4). There is no determinate
combination either.
In a moment we will see this that isn't quite adequate. Before we do, let us ask at a general level what we should make of Marquis's argument. We can ask two sorts of questions: (1) is it weaker than it seems, and (2) is it stronger than it seems -- perhaps unacceptably strong.
On the first point, recall that Thomson argues that even if the fetus is a person, it may still be acceptable to perform abortions in certain cases: at least (Thomson) in the cases of rape and threat to the mother's life. but also in the case in which the mother's future prospects are severely threatened, even if her life itself is not. Now Thomson talks of personhood rather than valuable futures. But persons are paradigms of the sort of being that has a potentially valuable future of the kind that Marquis is considering. And in any case, there is no reason to think that Thomson would disagree with Marquis about why killing is an evil. But she would probably insist nonetheless: abortion is
still justified in some cases. If her arguments are good, they bear on Marquis notwithstanding.
Turning to the second point, just how rich must a being's potential future be before Marquis's argument kicks in? Marquis himself points out that it may apply to some higher mammals. But consider the family cat. In the normal course of things, a cat has the capacity for a life filled with its own brand of happiness and pleasure. And just as the pain of an animal is an evil, other things being equal, so is its happiness and pleasure a good. So Marquis would seem to give us a strong reason for not killing animals with the capacities of cats or even cows. Marquis, in other words, may make a case for a rather extensive vegetarianism without having meant to.
While this might be so, it is not exactly a criticism of Marquis to point it out. After all, many people believe that we should, indeed, not kill animals except for very good reasons. Perhaps they are right, and perhaps Marquis provides a means of saying why.
Another problem is more difficult. Return to birth control. Marquis clearly had barrier methods in mind. But think abut the IUD. The IUD prevents pregnancy not by preventing conception but by preventing implantation. Does Marquis's view imply that the use of the IUD is immoral?
Many of us would find that hard to accept. A newly-fertilized ovum simply seems too unlike the sort of being from which Marquis's argument starts: a full-fledged human. (Remember: Marquis
begins by asking what is wrong with killing in the "typical" case.) And in fact, in what looks like a throw-away line, Marquis allows that this point might be correct,. He says that "morally permissible abortions will be rare indeed unless, perhaps, they occur so early in pregnancy that a fetus is not yet definitely an individual." Many people would think that the stage at which the IUD does its work is a good example. At
that stage of pregnancy, it might be thought, we really
don't have something that should be thought of as an individual in the sense of a definite
being. But if this is right, then we have to ask: at what stage
do we have a definite individual -- a definite
being?