The Birth of Population Ethics
Parfit in seven parts: Part VI
Parfit introduced two problems—the Non-Identity Problem, and the Repugnant Conclusion—that have perplexed philosophers ever since.
The Non-Identity Problem
An individual’s existence is fragile—not in the sense that they are easily killed, but in the less-appreciated sense that they very easily might never have existed in the first place. We’ve all heard the cliche about a flap of a butterfly’s wings causing a storm on the other side of the world. If such a storm changes people’s behaviour in the slightest, it could easily change when subsequent moments of conception occur. Different children would subsequently be born. Such reflections can bring us to see that we ourselves would almost certainly not have existed, had almost any major event in earlier history happened differently. (Should we then be glad, in a sense, that various historical atrocities occurred? An awkward question to answer honestly.)
Our fragility is curious to ponder. But its greatest philosophical significance emerges when we turn our attention to the future. Our actions—and especially large-scale collective actions, such as a nation’s choice of climate policy—do not just affect how well-off future people will be. They also affect who those future people will be. And this creates a problem, because we typically assume that an outcome can be worse only if it makes some individual(s) worse-off than they otherwise would have been. But identity-affecting actions make people exist who otherwise would not have existed at all. So they cannot be worse-off than they otherwise would have been (since they otherwise would not have been at all). But surely there’s something wrong with identity-affecting actions that result in greatly reduced quality of life for future generations? This is the Non-Identity Problem. To solve it, Parfit suggests, we “need to explain why we have a moral reason not to make these choices.”
Consider Parfit’s Depletion thought-experiment:
As a community, we must choose whether to deplete or conserve certain kinds of resources. If we choose Depletion, the quality of life over the next two centuries would be slightly higher than it would have been if we had chosen Conservation. But it would later, for many centuries, be much lower than it would have been if we had chosen Conservation.
Suppose that, even in the case of Depletion, everyone who ends up existing has lives that are at least barely worth living. But the later lives are much, much worse than the different lives that would have been lived had we chosen Conservation. If we accept the Narrow Person-Affecting Restriction—that an outcome can be bad only if it is worse for those who end up existing—then we seem committed to the absurd conclusion that Depletion is the morally better choice than Conservation. It makes some people (those who already exist) better-off, and nobody worse-off. The particular people who end up existing, even centuries in the future with low (but still positive) well-being, would if anything have self-interested reasons to be glad that we choose Depletion, for otherwise they would not have gotten to exist at all.
Indeed, if you poll everyone who ever ends up existing after we made our choice of Depletion, they would all have reason to be glad that we chose Depletion. If we chose Conservation, by contrast, existing people would be worse-off. Admittedly, distant future people might be more strongly glad of our choice, as they would get to live blessed lives. But depriving them of a blissful existence is no harm at all, so (on the Narrow view) this does not count against Depletion.
To avoid this absurdity, we must reject the Narrow view, and accept the surprising result that an outcome can be morally worse without being worse for anyone. In the case of Depletion, no individual is harmed, but the well-being of people in general is lower than it could have been, indicating that it is a worse outcome. There are two ways to vindicate this result. One is to appeal directly to impersonal value, such as the (total or average) well-being of humanity collectively. Alternatively, we may continue to appeal directly only to individual well-being, but (i) allow that existence can constitute a non-comparative benefit (if one’s subsequent existence is positive on the whole), and (ii) allow that an outcome can be worse because some alternative would have benefited people more—including those people who, as it happens, now do not get to exist. This Wide Person-Affecting View yields similar verdicts to the impersonal view, but does a better job of capturing the moral intuition that it is individual people that ultimately matter.
Some philosophers worry that, if we grant that there’s moral reason to want there to exist happy people in future, we risk being committed to implausible procreative obligations. But this doesn’t follow, as I argue in ‘Rethinking the Asymmetry’: we aren’t generally obliged to bring about good results, if doing so would be excessively burdensome or encroach upon bodily autonomy and reproductive freedom. The potential benefit to the future child is a factor to take into account when weighing procreative decisions, and it may help to tip the scales in close cases, but it is not by itself decisive.
A further possibility, to be explored more in the next section, is that the (non-instrumental) value of an additional life might depend upon what lives there already are. This is an implication of the Average view, for example: if what matters is average well-being, then adding an additional life of average well-being makes no non-instrumental difference (and adding a life of below-average well-being would even be bad in itself). The Total view, by contrast, counts every additional happy life as contributing positively to the overall value of the world. Neither option, it turns out, seems entirely palatable.
The Repugnant Conclusion
On the Total view, the value of an outcome is given by the sum value of the well-being that it contains. So, when comparing different options, the best one is whichever results in greater total wellbeing. Given some natural background assumptions, this view straightforwardly implies:
The Repugnant Conclusion: For any possible population of at least ten billion people, all with a very high quality of life, there must be some much larger imaginable population whose existence, if other things are equal, would be better, even though its members have lives that are barely worth living.
Zillions of people living mediocre lives sure doesn’t seem better than ten billion in utopia. But it turns out to be remarkably difficult to avoid this conclusion. Rejecting the Total view is not enough, for the Repugnant Conclusion also follows from the Mere Addition Paradox, to which we now turn.
Mere Addition
‘Mere addition’ is when we add additional lives—all above the baseline of lives worth living—to a world, without affecting the prior inhabitants in any way. Parfit claims, plausibly enough, that this process cannot make a world worse. After all, where’s the harm? How could it be bad to add intrinsically good lives, to no ill effect for anyone else? This suggests the following principle:
Mere Addition: If the only difference between worlds A and A+ is that the latter contains additional lives above the baseline, then A+ is no worse than A.
Next, note that it can only improve a world to reduce inequality in a way that also increases total welfare, while holding all else equal. Call such a shift ‘beneficial equality’. Beneficial equality licenses the move from A+ to a world B where the worse-off group in A+ is benefited more on net than the well-off group is harmed by the shift. If B is better than A+, which in turn is no worse than A, it follows (on standard assumptions) that B—a world of greater total but lesser average utility—is likewise better than A. We may iterate this process until we reach the repugnant world Z, with astronomic total utility but minuscule average utility.
These implications may lead us to examine the Mere Addition principle more closely, and perhaps insist that A+ is indeed a worse world than A. Why might one think this? Well, for one thing, the addition of worse (though not bad) lives alters the shape of the world as a whole, and not for the better. Whereas before we had a world full of flourishing, we now find mediocre lives in addition. That’s not to say that the mediocre lives are bad in themselves, or considered in isolation. But given how the rest of the world is, their addition may be considered undesirable.
Maybe. This response is far from costless, however. It requires us to reject Huemer’s Modal Pareto Principle (MPP):
For any possible worlds x and y, if, from the standpoint of self-interest, x would rationally be preferred to y by every being who would exist in either x or y, then x is better than y with respect to utility.
Why? Consider Benign Addition, which is like Mere Addition except that the original population is slightly better-off in A+ than they were in A. Then, since A+ would be rationally preferred over A by every individual who exists in either world, MPP implies that A+ is positively better than A. As before, it cannot be denied that the beneficially-equalized B is better than A+, and hence that B is better than A. Repeat the whole process enough times, and we end up with the Repugnant Conclusion that Z is better than A.
MPP is an intuitively compelling principle, representing the idea that ethics is fundamentally person-centered. There is a stark ideological divide between this moral individualism (which treats the value of individual lives as additive, entailing the Repugnant Conclusion) and the holistic view that rejects Benign Addition, against every individual’s wishes, for the sake of such impersonal considerations as the world’s “shape” or average utility. (For more on value holism, see sec. 7.2.2 of Parfit’s Ethics, where I offer a cautiously optimistic take on the approach, in contrast to Parfit.)
Parfit’s Solution
Parfit defends the Wide Dual Person-Affecting Principle, on which:
One of two outcomes would be in one way better if this outcome would together benefit people more [in aggregate], and in another way better if this outcome would benefit each person more.
Parfit recommends giving more weight to the latter consideration, favouring the consolidation of well-being into a smaller number of lives (within reason). To block the value of aggregate well-being from giving rise to the Repugnant Conclusion, Parfit suggests we might further claim that “great losses in the quality of people’s lives could not be outweighed by any increase in the sum of benefits, if these benefits came in the [creation of] lives of people whose quality of life would be much lower. I have started to defend this belief elsewhere.”
In a talk titled ‘How can we avoid the Repugnant Conclusion?’, Parfit advanced a principle of different-number-based imprecision:
When two possible worlds would contain different numbers of people, this fact makes these worlds less precisely comparable.
When adding lives of very slight value, Parfit suggests, the increased margin of imprecision might swamp the added value from their aggregate welfare, preventing the additions from qualifying as good on the whole. (Cf. this explanation of critical range theories.) This doesn’t vindicate the intuition that the repugnant world Z is positively worse than the starting utopia A, but it can at least accommodate the more moderate claim that Z is not better than A. So the solution is limited in scope, but relies upon less controversial commitments than radical holistic approaches to population ethics.
