Spare a Thought for the Billions of People Who Will Never Exist


A couple decides to have one child instead of two, or none instead of one. This happens all over the world. Billions of children are never conceived. How real is the loss of a life that never began? Is there a right to exist? Is there an ideal size of the world population?

These related questions become more pressing as population growth slows. China’s population is on track to peak before 2025. Population growth in the U.S. this year is likely to be the lowest in history except for one year, 1918. 

The late University of Oxford philosopher Derek Parfit wrestled with the question of the world’s ideal population in an influential 1984 book, Reasons and Persons. He didn’t delve into the carrying capacity of the planet, and he stayed away from the issue of abortion, which occurs after conception and thus raises a different set of concerns.

In an abstract, theoretical way, the British thinker presented what he called the “Repugnant Conclusion.” Here’s how he stated it: “For any possible population of at least 10 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.”

Parfit’s utilitarian logic was that if each person on the planet is happier alive than dead—even if just barely—then the total amount of happiness in an extremely large population, let’s say hundreds of billions, would be greater than the total happiness of a smaller population whose average happiness is greater. It’s simple arithmetic. But it’s also kind of awful, which is why Parfit called it repugnant (i.e., extremely distasteful; unacceptable).

One way to escape the Repugnant Conclusion is to maximize average happiness instead of total happiness. But that turns out to lead to a different kind of awfulness, as explained in an entry in the Stanford Encyclopedia of Philosophy by Gustaf Arrhenius, Jesper Ryberg, and Torbjorn Tannsjo. Maximizing average happiness would favor a world with one happy person over one with several billion slightly less happy people. It would also favor a world with several billion miserable people over a world with a single even more miserable person.

Another possible escape from the dilemma is to assert that some irreplaceable things are lost in the transition from a smallish, well-off population to a huge population of people just getting by. As Parfit put it, first Mozart goes away, then Haydn, etc., until all that’s left is “muzak and potatoes,” no amount of which can compensate for the loss of Mozart. (He should have capitalized Muzak.) That seems convincing, but Parfit and others found holes in that concept, too.

“The Repugnant Conclusion is a problem for all moral theories which hold that welfare at least matters when all other things are equal,” not just utilitarians, Arrhenius et al. write. They say “it has been surprisingly difficult to find a theory that avoids the Repugnant Conclusion without implying other equally counterintuitive conclusions.”

The question of the ideal world population size may never be resolved by philosophers. But you don’t have to be a philosopher to think about the lives that never happened. 

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