One objection to utilitarianism is its difficulty in dealing with questions of population change. For example, is it desirable to add more people to a population if the new additions have lives that are (a) worth living but (b) not quite as good as the lives of those already living? The larger population would have higher total utility but lower average utility. (Set aside concerns about negative externalities from population growth. Holding the happiness of the already-living sharpens the philosophical question.)
Derek Parfit’s “Mere Addition Paradox” (MAP) shows how both total and average utilitarianism can lead to bizarre and (seemingly) unpalatable conclusions. This article by Kai Chan has the best explanation of the MAP I’ve found, all in the first three pages. Here’s my quickie explanation: Suppose you have an existing population with relatively high utility. Someone proposes an addition like that described above (new people with lives that are worth living but below the previous average). Should we favor the proposal? The obvious answer seems to be “yes,” or at least “there’s no reason not to.” Adopting average rather than total utilitarianism could allow you to resist this conclusion – but that’s precisely what’s bizarre about average utilitarianism. So the new group is added on. Once those people are in existence, someone proposes a slight redistribution of resources that will make the new people better off and the old people worse off, with an overall net positive result (the utility gains exceed the utility losses). This proposal, too, is difficult to resist. But now consider the addition of yet another group of new people, with lives worth living but less satisfying than the lives of those who already exist. Repeat until you have a very large population of people with lives barely worth living. This is what Parfit calls the “repugnant conclusion.”
Now, what I’m wondering is whether an analytically similar problem might afflict some deontologists (e.g., natural rights theorists) who think they’ve managed to dodge the problems of utilitarianism. Say you have a population of people whose rights are respected perfectly. And suppose the population could be increased through the addition of a new group of people whose rights are mostly respected, albeit with the occasional violation. On what grounds could the deontologist resist the addition of this group? These people would, presumably, prefer to live despite the occasional rights violation. And in any case, if the deontologist believes in a right of procreation (or opposes any intervention to stop procreation), then he would have to allow the entrance of the new group.
Next step: Once we have the larger population, suppose we have the opportunity, via some change in policy, to redistribute the rights violations so that the new group has fewer rights violation, the older group has more, and the total number and severity of rights violations has fallen. Now, here the deontologist might object: right violations are not interpersonally comparable. The lesser violation of the rights of some does not compensate for the greater violations of the rights of others. But I don’t think this position will withstand scrutiny. The deontologist would have to resist changes in enforcement policy that would, say, prevent 1000 forcible rapes while allowing one more act of shoplifting. Or, at a minimum, he would have to shrug his shoulders. Similarly, the deontologists would have to resist (or at least be indifferent to) any change in the form of government that would result in lesser protection of any person’s rights. In practice, I don’t believe deontologists actually think that way. (Notice, for example, the many deontologist anarcho-capitalists who favor abolishing the state in favor of private protection agencies, even though such a change would assuredly cause some people’s rights to be better protected while at least a few others’ rights suffered.) So I think that reasonable deontologists would have to accept the proposed redistribution in rights protection.
Now repeat the process. The endpoint will be a society with the maximum number of people that could be sustained at some minimal level of rights protection.
The problem, for both utilitarians and deontologists, results from an intransitivity driven by the distinction between actual and potential persons. For both groups, it seems strange to regard non-existent people as having morally relevant interests (for the utilitarians) or inherent moral rights (for the deontologists). Yet once such people do exist, their interests and/or rights suddenly matter. For utilitarians, that means weighing their interests against those of other real people. For deontologists, it means respecting and protecting their rights. That might seem to require no sacrifice of the rights of others – until we recognize that rights protection is costly, and therefore we can’t avoid trade-offs in rights protection. Within a given regime, the trade-off is felt in the allocation of law enforcement resources. Across regimes, the trade-off is felt in the choice of which regime to favor. To make the problem yet more vexing, the people who exist under each regime will differ (because, at a minimum, sensitive dependence on initial conditions means that different sperm will meet different ova).
For related thoughts about deontology versus consequentialism, see my post on lexicographic orderings.