A simple argument for the badness of human extinction
How bad would it be to cause human extinction? ‘‘If we do not soon destroy ourselves’, write Carl Sagan and Richard Turco, ‘but instead survive for a typical lifetime of a successful species, there will be humans for another 10 million years or so. Assuming that our lifespan and numbers do not much grow over that period, the cumulative human population—all of us who have ever lived—would then reach the startling total of about a quadrillion (a 1 followed by 15 zeros). So, if nuclear winter could work our extinction, it is something like a million times worse (a quadrillion divided by a billion) than the direct effects of nuclear war—in terms of the number of people who would thereby never live.’
You may agree that that this would be far worse than killing ‘only’ eight billion people and makes it much more important to avoid even the risk of doing so. That’s certainly the view of leading longtermists. But then you’ve probably had the experience of arguing with people who don’t accept this claim at all. Trying to derive it from total utilitarianism—seemingly the most straightforward approach—runs into notorious difficulties. Many philosophers deny it. Instead, like many laypeople, they accept what John Broome calls the ‘intuition of neutrality’: ‘for a wide range of levels of lifetime wellbeing, between a bad life and a very good life, we intuitively think that adding a person at that level is neutral.’
Broome thinks the intuition of neutrality must be wrong, and offers some proofs. I think there’s a simpler reason to doubt it. (N.B.: I’ll bracket the effects of our survival on non-humans.) Suppose a government is considering developing vaccines against two strains of flu. If the first mutates and crosses into the human population, it will kill seven billion people immediately. After that, most people will develop immunity, but it will still kill ten million people a year for the next thousand years. If the second virus mutates and crosses into the human population, it will kill everybody on earth. Each virus is estimated to have a 1/1000 chance of mutating.
Most of us will agree—I hope—that the government shouldn’t discount the ten billion future deaths that the first virus would cause just because they would arrive in the future. It should count the expected deaths from an outbreak as 17 million (1/1000 x 17 billion). In contrast, the expected deaths if the second virus breaks out are only 8 million (1/1000 x 8 billion). If additional human lives have no value in themselves, that implies that the government would have more reason to take precautionary measures against a virus that would kill most of us than one that would kill all of us, even if the probabilities were equal. If it could only afford to develop vaccines against one of them, it should choose the first.
That seems to me a reductio. Do you agree? Or am I missing something?
Postscript: Judging by the first two comments on this post, I must have failed to make myself clear. I believe the second scenario is at least as bad as the first, and that this undermines the ‘intuition of neutrality’. See my reply below.
Sorry are you claiming that there is no value to extra lives but extra deaths are still bad so the virus that keeps killing living people is worse?
If so it seems the issue is that if extra lives are valueless, so are extra deaths.
Maybe I’m misunderstanding, but if
we totally discounted what happens to future/additional people (even stronger than no reason to create them), and only cared about present/necessary people, and
killing everyone/extinction means killing all present/necessary people (extinction now, not extinction in the future) and no one else ever existing,
then, conditional on the given virus mutating
the first virus kills 7 billion + possibly several million more people who presently/necessarily exist, but less than 8 billion present/necessary people
the second virus kills everyone, 8 billion present/necessary people
2 kills more present/necessary people, so we’d want to prevent it.
EDIT: It looks like you pointed out something similar here.
Thanks—that’s very helpful. On a wide person-affecting view, A would be worse, but if we limit our analysis to present/necessary people, then outcome B would be worse. That had not occurred to me, probably because I find narrow person-affecting views so implausible.
However, it doesn’t seem very damaging to my argument. If we take a hardcore narrow person-affecting view, the extra ten billion deaths shouldn’t count at all in our assessment. But surely that’s very hard to believe.
Alternatively, if we adopt what Parfit calls a ‘two tier view’, then we’d give some weight to the deaths of the contingent people in scenario A, but less than to the deaths of present/necessary people. Even if we discounted them by a factor of five, however, scenario A would still be worse than scenario B. What is more, we can adjust the numbers:
Scenario A: Seven billion necessary people die immediately and ten million die annually for the next 10,000 years for a total of 107 billion. Most of the future people are contingent.
Scenario B: Eight billion die at once. All are necessary people.
On the two tier-view, deaths of necessary people would have to be more than a hundred times as bad as those of contingent ones for B to be worse. That is hard to believe.
Bottom line:
Plausible person-affecting views will judge A better than B.
That A is better than B is, however, implausible.
∴ No otherwise plausible person-affecting view renders a plausible judgement about this case.
∴ Person-affecting views do not provide a convincing rationale for rejecting my argument against the Intuition of Neutrality.
Do you intend for the population to recover in B, or extinction with no future people? In the post, you write that the second virus “will kill everybody on earth”. I’d assume that means extinction.
If B (killing 8 billion necessary people) does mean extinction and you think B is better than A, then you prefer extinction to extra future deaths. And your argument seems general, e.g. we should just go extinct now to prevent the deaths of future people. If they’re never born, they can’t die. You’d be assigning negative value to additional deaths, but no positive value to additional lives. The view would be antinatalist.
Or, if you think B is just no worse than A (equivalent or incomparable), then extinction is permissible, in order to prevent the deaths of future people.
If you allow population recovery in B, then (symmetric) wide person-affecting views can say B is better than A, although it could depend on how many future/contingent people will exist in each scenario. If the number is the same or larger in B and dying earlier is worse than dying later, then B would be better. If it’s lower in B, then you may need to discount some of the extra early deaths in A.
Thanks! I was indeed assuming total extinction in B. As you say, antinatalist views will prefer A to B. If antinatalism is correct, then my argument against the intuition of neutrality fails.
Our discussion has been helpful to me, because it’s made me realise that my argument is really directed against views that accept the intuition of neutrality, but aren’t either (a) antinatalist or (b) narrow person-affecting.
That does limit its scope. Nevertheless, common sense morality seems to accept the intuition of neutrality, but not anti-natalism. Nor does it seem to accept narrow person-affecting views (thus most laypeople’s embrace of the No Difference View when it comes to the non-identity problem). It’s that ‘moderate middle’, so to speak, at whom my argument is directed.
Still, I think your argument is in fact an argument for antinatalism, or can be turned into one, based on the features of the problem to which you’ve been sensitive here so far. If you rejected antinatalism, then your argument proves too much and you should discount it, or you should be more sympathetic to antinatalism (or both).
You say B prevents more deaths, because it will prevent deaths of future people from the virus. But it prevents those future deaths by also preventing those people from existing.
So, for B to be better than A, you’re saying it’s worse for extra people to exist than not exist, and the reason it’s worse is that they will die. Or that the will die early, but early relative to what? There’s no counterfactual in which they live longer, the way you’ve set the problem up. They die early relative to other people around them or perhaps without achieving major life goals they would have achieved if they didn’t die early, I guess.
Similarly, going extinct now prevents more deaths from all causes, including age-related ones, but also everything that causes people to die early, like car accidents, war, diseases in young people, etc.. The effects are essentially the same.
What’s special about the virus in this hypothetical vs all other causes of (early) death in humans?
So, we should prevent (early) deaths by going extinct now, or collectively refusing to have children, if the alternative is the status quo with many (early) deaths for a long time. That looks like an principle antinatalist position.
I think we’re talking past each other. My claim is that taking precautionary measures in case A will prevent more deaths in expectation (17 billion/1000 = 17 million) than taking precautionary measures in case B (8 billion/1000 = 8 million). We can all agree that it’s better, other things being equal, to save more deaths in expectation than fewer. On the Intuition of Neutrality, other things seemingly are equal, making it more important to take precautionary measures against the virus in A than against the virus in B.
But this is a reductio ad absurdum. Would it really be better for humanity to go extinct than to suffer ten million deaths from the virus per year for the next thousand years? And if not, shouldn’t we accept that the reason is that additional (good) lives have value?
I don’t think it’s true that other things are equal on the intuition of neutrality, after saying there are more deaths in A than B. The lives and deaths of the contingent/future people in A wouldn’t count at all on symmetric person-affecting views (narrow or wide). On some asymmetric person-affecting views, they might count, but the bad lives count fully, while the additional good lives only offset (possibly fully offset) but never outweigh the additional bad lives, so the extra lives and deaths need not count on net.
On the intuition of neutrality, there are more deaths that count in B, basically except if you’re an antinatalist (about this case).
What person-affecting views satisfying neutrality do you imagine would recommend B/extinction/taking precautions against A here?
For an argument against neutrality that isn’t just against antinatalism, I think you want to define B so that it’s better than or as good as A for necessary people. For example, the virus in B makes everyone infertile without killing them (but the virus in A kills people). Or, fewer people are killed early on in B, and the rest decide not to have children. Or, the deaths in A (for the necessary people) are painful and extended, but painless in B.
Your argument would only establish that we shouldn’t be indifferent to (or discount or substantially discount) future lives, not that we have reason to ensure future people are born in the first place or to create people. Multiple views that don’t find extinction much worse than almost everyone dying + population recovery could still recommend avoiding the extra deaths of future people. Especially “wide” person-affecting views.[1]
On “wide” person-affecting views, if you have one extra person Alice in outcome A, but a different extra person Bob in outcome B, and otherwise the same people in both, then you treat Alice and Bob like the same person across the two outcomes. They’re “counterparts”. For more on this, and how to extend to different numbers of non-overlapping people between A and B, see Meacham, 2012, section 4 (or short summary in Koehler, 2021) and Thomas, 2019, section 5.3. I also discuss some different person-affecting views here.
Under wide views, with the virus that kills more people, the necessary people+matched counterparts are worse off than with the virus that kills fewer people.
(I’d guess there are different ways to specify the intuition of neutrality; your argument might succeed against some but not others.)
Some versions of negative preference utilitarianism or views that minimize aggregate DALYs might, too, but if the extra early deaths prevent additional births, then in fact killing more people with the viruses could prevent more deaths overall, and that could be better on these views. These are pretty antinatalist views. That being said, I am fairly sympathetic to antinatalism about future people, but more so because I don’t think good lives can make up for bad ones.
Thanks! Perhaps I haven’t grasped what you’re saying. In my example, if the first virus mutates, it’ll be the one that kills more people--17 billion. If the second virus mutates, the entire human population dies at once from the virus, so only 8 billion people die in toto.
On either wide or narrow person-affecting views, it seems like we have to say that the first outcome—seven billion deaths and then ten million deaths a year for the next millennium—is worse than the second (extinction). But is that plausible? Doesn’t this example undermine person-affecting views of either kind?
Actually, I guess that on a narrow person-affecting view, the first outcome would not be worse than the second, because plausibly a pandemic of this kind would affect the identities of subsequent generations. Assuming the lives of the people who died were still worth living, while the first virus would be worse for people—because it would kill ten billion more of them—it would not, for the most part, be worse for particular people. But that seems like the wrong kind of reason to conclude that A is better than B.
Thanks for the feedback! As a matter of fact, I agree that the second scenario is worse. My aim was to undermine the ‘intuition of neutrality’—the claim that we have no reason to create additional happy lives. Perhaps it’ll help to state the argument in the form of a syllogism:
Premise: If the government can either (A) save an expected 7 million human lives now and another expected 8 million over the next thousand years or (b) save humanity from destruction, it’s at least as good to do (B).
Intuition of Neutrality: It’s good to save or improve existing lives, but it isn’t good to create new ones. (Or to quote Jan Narveson, ‘We are in favor of making people happy, but neutral about making happy people.’ )
If the government adopts policy A, it will save 17 million lives in expectation.
If the government adopts policy B, it will save 8 million lives in expectation.
∴ Policy A will save more existing lives in expectation than policy B (by 3 and 4)
∴ If the Intuition of Neutrality is correct, policy A must be better than policy B (by 2 and 5)
But policy A is not better than policy B (by 1)
∴ The Intuition of Neutrality must be false (by 6 and 7).
I don’t think 6 follows. Preventing the early deaths of future people does not imply creating new lives or making happy people. The two statements in each version of the intuition of neutrality separated by the “but” here are not actually exhaustive of how we should treat future people.
I don’t think this argument is sound. In your EV calculation you’re including the expected deaths over the thousand year period but excluding the expected lives over that same period. There’s an asymmetry in this comparison.
Also, I don’t see how x number deaths of a given species could be worse than the extinction of that species. The way I see it the first choice is save k lives over a thousand years, but the second choice is save k less lives over the same period and loose all future lives after that, forever.
The government should defend against the second case.