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How many people should there be?

This is the core debate in a whole branch of philosophy known as population ethics. The debate has two polar extremes. One extreme, anti-natalism, argues that creating humans at all is immoral.

The other extreme is the view that creating humans is always a good thing — even if that results in a less happy population on average. (Most people are somewhere in between: More moderate philosophers who want a smaller population argue that humans produce carbon emissions, wreck animal habitats, and use up scarce natural resources.)

The avidly natalist view is often identified with religious commitment, in Abrahamic faiths given Genesis’s instruction to “be fruitful and multiply.” But Torbjörn Tännsjö, a philosopher at Stockholm University, thinks secular people should embrace population growth as well. Humanity is great, he argues, and we should make sure there are as many human beings living good lives as there possibly can be. This view implies that we could be suffering from an underpopulation problem, not an overpopulation problem.

Put differently, he embraces what philosophers call the “repugnant conclusion”: the idea that adding more humans with good lives is always valuable, and so we should aim for the biggest population we can support, even if that means average happiness goes down. The idea that we should try to create a world teeming with miserable people whose lives are barely worth living strikes most philosophers as, indeed, repugnant. But Tännsjö begs to differ.

Tännsjö and I discussed his argument over Skype. A transcript, edited for length and clarity, follows.

Dylan Matthews

Your central argument is we should care very, very much about making sure that humanity keeps going, that there’s a lot of value in the continued existence of humanity. And when you put it that way, I think a lot of people would nod and say, “Yeah, that seems right.” Who are you arguing against? What voices are saying this isn’t such an important thing?

Torbjörn Tännsjö

Very influential philosophers have argued that it doesn’t matter, and some have even argued that it’s better to have no humans around.

That sounds ridiculous to my ears, and to most ears, I suppose, but they have cogent arguments. I think it’s of the utmost importance that we go on, generation after generation, the more the better. And it’s amazing that it’s so difficult to come up with a good philosophical rationale behind this commonsense view. When you start to articulate a rationale behind this commonsense view, you wind up in all sorts of theoretical complications.

There are implications behind the commonsense view that most philosophers think are blatantly wrong. They think of it as an absurd position, as a “repugnant conclusion” that follows from the argument.

Dylan Matthews

What is the repugnant conclusion? Why does it strike so many philosophers as unacceptable?

Torbjörn Tännsjö

Ordinary human lives are worth living. But if you want to continue with humanity, then you of course want to continue as long as possible.

But why should we do that? The simplest explanation is that we should maximize the sum total of happiness in the universe, and that by going on, generation after generation, we accumulate more happiness.

[The objection to this view asks] you to compare a situation with 10 billion extremely happy people to a situation where enormous numbers of people [way more than 10 billion] live lives that are barely worth living.

If they are many enough, that world with a huge population and a low quality of life contains more happiness than the smaller world with 10 billion extremely happy people. Many philosophers have claimed that this world — with a great many people with heads just above the water — is worse than the world with just these 10 billion extremely happy people.

On my view, it’s the other way around. The extremely well-populated world is better. It is better when many people are at a lower quality of life than a few at a higher quality of life.

Dylan Matthews

In much of the world over the last 50 years, there’s been a lot of panic about overpopulation. You might be able to get people on board with the idea that it’s important for humanity to keep going, but it’s hard to get people on board with the idea that it’d be better to have 10 billion people rather than the 7.5 billion we have now, let alone a much bigger number like 100 billion.

What mistake are people who worry about overpopulation making? Is it an empirical mistake — are they just wrong about what this would mean in practice — or a deeper philosophical mistake?

Torbjörn Tännsjö

It is a thorny empirical question.

The crucial thing is not how many people are living right now, but the sum total of happiness. Perhaps we should be fewer now to be able to go on for millions of years. Some people have a theory that we’re perhaps too many right now, and I don’t object to that. The idea is that we should be as many as possible at each point in time and go on for as long as possible. The rationale behind this is the idea that we should maximize the sum total of happiness.

Dylan Matthews

What would this imply for personal autonomy and choice? I think people hear “we should be as many as possible” and start imagining the denial of the right to choose whether to have kids, to use birth control, and otherwise imposing incredible burdens on women, especially, to procreate more. That conclusion does seem rather repugnant to me. How do you avoid it?

Torbjörn Tännsjö

There are no problems from the point of view of personal autonomy. This is really a political and social decision we have to make. How many people is enough? Are we too many or are we too few? Once you have settled on that empirical question, given this moral background, then I think you can leave it to human spontaneity — to have children or not, to have an abortion or not.

Dylan Matthews

So if we want there to be as many people as possible — since it’s likely that most people who will ever live will live in the future — that implies that our focus should be on people thousands, even millions of years in the future, not people living right now. Is that true?

Torbjörn Tännsjö

There is no discount for time. Future generations count as much as we do. It is the sum total that is important. It’s very difficult, I think, to find a middle ground between this idea and the extreme idea that only those who exist are of moral importance.

Some moral philosophers think of morality as a way of relating to one another. If there are other people around, then there are things we aren’t allowed to do. If you just put a happy ending to humanity, then there is no one left to complain, so there is no problem anymore.

That’s one extreme view, and my opposite view, which is perhaps also extreme, is that everyone counts, even in the far future.

Of course, some people are satisfied with this idea that there will be an end of humanity anyway, and there will be no one there to complain. I think it’s a terrible view, a horrendous view, but some of my colleagues adhere to it.

Dylan Matthews

What’s most horrendous about that? What’s so morally appalling about the idea that humanity will end anyway, so we should accept that and not fight extinction too hard?

Torbjörn Tännsjö

I would compare it with my individual life. It is true that it will also have an end. But few people say, “I’m 13 years old, I’m having a terrific life right now, why not end it?”

Many people would say something is lost here. You deprive yourself of possible good experiences in the future. Then again, those who adhere to this idea could say, “Yes, but then you’re not around and there’s no one who could complain on your behalf.”

Perhaps that kind of comparison could make people understand that there is something wrong with the idea of putting an end to humanity.

Dylan Matthews

What does your view imply about longevity issues? I share your intuition that it really matters that we keep humanity going for a long while. But I’m also drawn to the argument Derek Parfit made, that my individual identity isn’t what matters because I’m just bound up in this broader project of humankind. So as long as humankind keeps going, it’s not that important that I personally live to 100 or 120 or what have you, even if I myself might enjoy doing so.

Torbjörn Tännsjö

Morally speaking, we’re exchangeable. We will be exchanged. In a way, it doesn’t matter.

This sounds awkward after what I just said. I do lose by losing my life, of course, but if there’s compensation in the form of another life, I do not object to it from a moral point of view.

I see no real point in prolonging our lives. These ideas about defeating death and living indefinitely long lives, that’s a dystopia. We will do it as soon as we can because people cling to life even if quality goes down, but from the point of view of the universe, this is a bad idea. It’s better that we exchange one generation for another. People can bring new and fresh eyes and enjoy it in a way we lose as we get older.

Dylan Matthews

What does your philosophy imply for treatment of animals? I’m a vegetarian. One thing that might do is reduce the number of animals there are in the world, by reducing demand for meat products and spurring meat producers to breed fewer cattle, fewer pigs, fewer chickens, etc.

If those animals’ lives would have been so bad as to not be worth living, maybe that’s fine. But if their lives are even barely worth living, am I making a mistake?

Torbjörn Tännsjö

Your argument here is my argument. You ought to eat meat, for the sake of the animals. That doesn’t mean, of course, that we should be complacent when they lead terrible lives in a factory farm. But we should be picky in our eating, and only eat animals who’ve had a good life and a good death. Many animals get just as good deaths as we humans do.

You are sending the wrong message by being a vegetarian. The message is that they shouldn’t be brought up at all, which is not a murderous implication but a rather sad one anyway. It’s anti-natalist on the behalf of those animals.

Dylan Matthews

If someone reads your argument and gets persuaded, how should they live their life differently? I shouldn’t be a vegetarian, but should I suddenly switch all my activity to trying to prevent human extinction?

Torbjörn Tännsjö

It has radical political implications. I don’t believe much in changing the world through your own behavior, consumer behavior, or anything like that. It’s not efficacious in a way that political action is.

I think we’re facing an enormously crucial time now. In particular, global warming is threatening us. It poses an existential collective threat to humanity. We need to take action.

I admire those who take to the streets for demonstrations. I admire Greta [Thunberg], the Swedish girl who visited the pope and who travels around the world getting young people dedicated to this task of saving the world. There is no Planet B, as they say, and I think they are perfectly right about this, and we should join them. I do — I play the clarinet in an orchestra and we take to the streets and take part in those rallies. We’re fighting for the existence of the human species, and other sentient beings as well.