The mere addition paradox was a thought experiment devised by the late and great analytic philosopher Derek Parfit. The problem in population ethics pushes us toward a conclusion that seems deeply counterintuitive—so much so that Parfit famously labeled it “repugnant.” In this paper, I will attempt to show that while total utilitarianism succumbs to Parfit’s repugnant conclusion, deontology and virtue ethics offer more plausible ways of resisting it.
To start, consider a population of 100,000 who all live very happy lives. We can call this group population A. All members of population A have a high quality of life, possibly related to the fact that they have more resources per person. In a complete other world, there exists population B. Population B has 10x as many people as population A, yet, all members of population B would still agree that they lead lives that are very much worth living. However, population B’ers certainly struggle through life much more than population A’ers.
Now comes the addition part of the paradox. Imagine you have two worlds. One world has population A and population B (A+B) in it, and the other just has population A. Now, here Parfit argues that if we are looking to maximize happiness for the greatest number of people, A+B should be a better world than A. This is because A+B has all the extremely happy people in A, plus the moderately happy people in B. Thus, A+B is better overall because everyone is still happy and the total number of people is larger—hence there is more total happiness.
Now consider group C. Group C is larger than both populations A and B, but the people in it are less happy than either group as well. We can repeat the same step of comparison again here, but now between A+B and A+B+C. Some ethical theories assert that A+B+C is a better population than A+B for the same reasoning as above: A+B+C contains all of the people in A+B, plus another large group of people (C), that still enjoy lives worth living. The paradox is that population groups can continue to be added to this A+B+C, each one having more people but a lower average quality of life until we reach something like A+B+C…X+Y+Z, an enormous population consisting of people whose lives, on average, are barely worth living. Under certain moral theories, this addition is not only permitted but considered ethical.
I’d like to just make it clear that in this thought experiment, the addition of subsequent groups does not diminish the quality of life previous groups experience. Even in population A+B+C…X+Y+Z, we still assume that the lucky few in population A live their same lavish lifestyles. Population groups X, Y, and Z, all lead lives with a limited amount of resources, namely, the goods that the previous population groups do not consume.
The mere addition paradox closely resembles overpopulation on a planet with limited resources. The repugnant conclusion is that if we are hell-bent on maximizing total welfare, a population on earth that contains our current 8 billion plus 8 billion other people, who live lives barely worth living, is better. The repugnant part is that many of us have the strong intuition that a world full of people whose lives are just barely worth living is worse—not better—than a smaller world where everyone flourishes.
In case it wasn’t clear, the mere addition paradox is an attack on total utilitarianism. The conclusion reached by mere addition is repugnant based on the fact that nothing else is considered in the calculus of lives other than total happiness or well-being. As adding more lives gives more capacity for happiness, a total utilitarian should accept the repugnant conclusion, and the world-wide disparity that emerges with it, as acceptable.
However, utilitarians have a way to weasel out of this conclusion. If somehow the addition of more people to the world brings down the total happiness of the already-existing people, then a utilitarian has a justified reason to oppose the repugnant conclusion. Yet, if we assume that an additional 8 billion people have no significant effect on the total happiness of our lives—which isn’t as far-fetched as it sounds, given how many resources we currently waste—then a utilitarian is almost forced to accept the repugnant conclusion.
An adherent of deontology would strongly oppose the repugnant conclusion. Kantian deontology judges actions and policies based on whether they treat persons as ends in themselves and whether the principles behind them could be universalized. If we use the universal maxim formulation of the categorical imperative, one could plausibly universalize a belief regarding a certain level of well-being that everyone should have. This could be like, “it is unethical to be deprived of drinking water.” The above statement should be rationally accepted. Thus, since adding more and more people to the world would break this formulation, it cannot be ethical to add billions to the world. Additionally, one could do this same universalization with countless other aspects of life, such as autonomy, food, shelter, etc. Since overpopulation would continue to strip these rights away from the groups of people that are subsequently added, the repugnant conclusion will continue to fail.
A deontologist would likely choose the world (out of A, A+B, A+B+C, etc) that allows people to have the most rights. This framework most naturally supports choosing a world like A, or perhaps A+B, where each person’s basic rights are firmly secured. As the goal of deontology is to prioritize the lives of already living people, less emphasis overall is placed on maximizing possible future happiness.
Finally, a virtue ethicist would evaluate the repugnant conclusion by asking what a virtuous person or a flourishing community would strive for. Prized virtues such as practical wisdom and justice would hold that we should care for not only people who exist, but that we should also ensure that those who inhabit our world have the resources to live meaningful lives. Deliberately choosing a world that maximizes total happiness could be interpreted as carrying a shallow view of human nature and treating people simply as containers for value. Due to this, the repugnant conclusion would likely be rejected on the grounds that it reveals a distorted sense of what is valuable in life. A smaller world, filled with people who have the ability to flourish, will embody the flourishing that a virtue ethicist prizes.
Yet, it would be naive to insist that flourishing is a binary variable. I think most will agree with the fact that some can flourish more than others. Given this statement, the repugnant conclusion is thrown a lifeline. If adding more people to the world harms population A a negligible amount but allows population B to flourish, say, 70 percent, then shouldn’t a virtue ethicist agree with at least one population group addition? Of course, the repugnant conclusion cannot be entirely reached through virtue ethics. But a few additions can possibly be made—and maybe a world such as A+B+C is seen as the best.
The mere addition paradox doesn’t tell us which moral theory is correct, but it does expose the strange trade-offs that come with maximizing the “goodness” of a world. Total utilitarianism delivers a clean mathematical answer but risks treating people as containers for tiny amounts of value. On the other hand, deontology and virtue ethics resist that picture by insisting on thresholds of dignity that cannot be breached. Regardless of who we side with, Parfit’s paradox forces us to confront an unsettling question: should we care more about how many lives exist, or about how fully the lives that do exist are lived?