I’m a Postdoctoral Research Fellow at Oxford University’s Global Priorities Institute.
Previously, I was a Philosophy Fellow at the Center for AI Safety.
So far, my work has mostly been about the moral importance of future generations. Going forward, it will mostly be about AI.
You can email me at elliott.thornley@philosophy.ox.ac.uk
Thanks!
Your point about time preference is an important one, and I think you’re right that people sometimes make too quick an inference from a zero rate of pure time preference to a future-focus, without properly heeding just how difficult it is to predict the long-term consequences of our actions. But in my experience, longtermists are very aware of the difficulty. They recognise that the long-term consequences of almost all of our actions are so difficult to predict that their expected long-term value is roughly 0. Nevertheless, they think that the long-term consequences of some very small subset of actions are predictable enough to justify undertaking those actions.
On the dice example, you say that the infinite set of things that could happen while the die is in the air is not the outcome space about which we’re concerned. But can’t the longtermist make the same response? Imagine they said: ‘For the purpose of calculating a lower bound on the expected value of reducing x-risk, the infinite set of futures is not the outcome space about which we’re concered. The outcome space about which we’re concerned consists of the following two outcomes: (1) Humanity goes extinct before 2100, (2) Humanity does not go extinct before 2100.’
And, in any case, it seems like Vaden’s point about future expectations being undefined still proves too much. Consider instead the following two hypotheses and suppose you have to bet on one of them: (1) The human population will be at least 8 billion next year, (2) The human population will be at least 7 billion next year. If the probabilities of both hypotheses are undefined, then it would seem permissible to bet on either. But clearly you ought to bet on (2). So it seems like these probabilities are not undefined after all.
Thanks!
And agreed! The title of the paper is intended as a riff on the title of the chapter where Arrhenius gives his sixth impossibility theorem: ‘The Impossibility of a Satisfactory Population Ethics.’ I think that an RC-implying theory can still be satisfactory.
Thanks for your comment! I think the following is a closer analogy to what I say in the paper:
Suppose apples are better than oranges, which are in turn better than bananas. And suppose your choices are:
An apple and bananas for sure.
An apple with probability and an orange with probability , along with oranges for sure.
Then even if you believe:
One apple is better than any amount of oranges
It still seems as if, for some large and small , 2 is better than 1. 2 slightly increases the risk you miss out on an apple, but it compensates you for that increased risk by giving you many oranges rather than many bananas.
On your side question, I don’t assume completeness! But maybe if I did, then you could recover the VNM theorem. I’d have to give it more thought.
Thanks! Your points about independence sound right to me.
Ah no, that’s as it should be! is saying that is one of the very positive welfare levels mentioned on page 4.
Thanks! This is a really cool idea and I’ll have to think more about it. What I’ll say now is that I think your version of lexical totalism violates RGNEP and RNE. That’s because of the order in which I have the quantifiers. I say, ‘there exists p such that for any k...’. I think your lexical totalism only satisfies weaker versions of RGNEP and RNE with the quantifiers the other way around: ‘for any k, there exists p...’.
Yes, that all sounds right to me. Thanks for the tip about uniformity and fanaticism! Uniformity also comes up here, in the distinction between the Quantity Condition and the Trade-Off Condition.
I remember Toby Ord gave a talk at GPI where he pointed out the following:
Let L be long-term value per unit of resources and N be near-term value per unit of resources. Then spending 50% of resources on the best long-term intervention and 50% of resources on the best near-term intervention will lead you to split resources equally between A and C. But the best thing to do on a 0.5*(near-term value)+0.5*(long-term value) value function is to devote 100% of resources to B.
How about Dylan Balfour’s ‘Pascal’s Mugging Strikes Again’? It’s great.
Sweet! I’ve messaged him.
Nice post! I share your meta-ethical stance, but I don’t think you should call it ‘moral quasi-realism’. ‘Quasi-realism’ already names a position in meta-ethics, and it’s different to the position you describe.
Very roughly, quasi-realism agrees with anti-realism in stating:
(1) Nothing is objectively right or wrong.
(2) Moral judgments don’t express beliefs.
But, in contrast to anti-realism, quasi-realism also states:
(3) It’s nevertheless legitimate to describe certain moral judgments as true.
The conjunction of (1)-(3) defines quasi-realism.
What you call ‘quasi-realism’ might be compatible with (2) and (3), but its defining features seem to be (1) plus something like:
(4) Our aim is to abide by the principles that we’d embrace if we were more thoughtful, informed, etc.
(1) plus (4) could point you towards two different positions in meta-ethics. It depends whether you think it’s appropriate to describe the principles we’d embrace if we were more thoughtful, etc., as true.
If you think it is appropriate to describe these principles as true, then that counts as an ideal observer theory.
If you think it isn’t appropriate to describe these principles as true, then your position is just anti-realism plus the claim that you do in fact try to abide by the principles that you’d embrace if you were more thoughtful, etc.
My impression is that each family of person-affecting views avoids the Dutch book here.
Here are four families:
(1) Presentism: only people who presently exist matter.
(2) Actualism: only people who will exist (in the actual world) matter.
(3) Necessitarianism: only people who will exist regardless of your choice matter.
(4) Harm-minimisation views (HMV): Minimize harm, where harm is the amount by which a person’s welfare falls short of what it could have been.
Presentists won’t make trade 2, because Alice doesn’t exist yet.
Actualists can permissibly turn down trade 3, because if they turn down trade 3 then Alice will actually exist and her welfare matters.
Necessitarians won’t make trade 2, because it’s not the case that Alice will exist regardless of their choice.
HMVs won’t make trade 1, because Alice is harmed in World 2 but not World 1.
Agreed
Yup!
Okay, that seems fair. And I agree that the Dutch book is a good argument against the person-affecting intuitions you lay out. But the argument only shows that people initially attracted to those person-affecting intuitions should move to a non-Dutch-bookable person-affecting view. If we want to move people away from person-affecting views entirely, we need other arguments.
The person-affecting views endorsed by philosophers these days are more complex than the families I listed. They’re not so intuitively ridiculous (though I think they still have problems. I have a couple of draft papers on this.).
Also a minor terminological note, you’ve called your argument a Dutch book and so have I. But I think it would be more standard to call it a money pump. Dutch books are a set of gambles all taken at once that are guaranteed to leave a person worse off. Money pumps are a set of trades taken one after the other that are guaranteed to leave a person worse off.
I’m just trying to fix that discrepancy.
I see. That seems like a good thing to do.
Here’s another good argument against person-affecting views that can be explained pretty simply, due to Tomi Francis.
Person-affecting views imply that it’s not good to add happy people. But Q is better than P, because Q is better for the hundred already-existing people, and the ten billion extra people in Q all live happy lives. And R is better than Q, because moving to R makes one hundred people’s lives slightly worse and ten billion people’s lives much better. Since betterness is transitive, R is better than P. R and P are identical except for the extra ten billion people living happy lives in R. Therefore, it’s good to add happy people, and person-affecting views are false.
I think in ordinary cases, necessitarianism ends up looking a lot like presentism. If someone presently exists, then they exist regardless of my choices. If someone doesn’t yet exist, their existence likely depends on my choices (there’s probably something I could do to prevent their existence).
Necessitarianism and presentism do differ in some contrived cases, though. For example, suppose I’m the last living creature on Earth, and I’m about to die. I can either leave the Earth pristine or wreck the environment. Some alien will soon be born far away and then travel to Earth. This alien’s life on Earth will be much better if I leave the Earth pristine. Presentism implies that it doesn’t matter whether I wreck the Earth, because the alien doesn’t exist yet. Necessitarianism implies that it would be bad to wreck the Earth, because the alien will exist regardless of what I do.
Hi Vaden,
Cool post! I think you make a lot of good points. Nevertheless, I think longtermism is important and defensible, so I’ll offer some defence here.
First, your point about future expectations being undefined seems to prove too much. There are infinitely many ways of rolling a fair die (someone shouts ‘1!’ while the die is in the air, someone shouts ‘2!’, etc.). But there is clearly some sense in which I ought to assign a probability of 1⁄6 to the hypothesis that the die lands on 1.
Suppose, for example, that I am offered a choice: either bet on a six-sided die landing on 1 or bet on a twenty-sided die landing on 1. If both probabilities are undefined, then it seems I can permissibly bet on either. But clearly I ought to bet on the six-sided die.
Now you may say that we have a measure over the set of outcomes when we’re rolling a die and we don’t have a measure over the set of futures. But it’s unclear to me what measure could apply to die rolls but not to futures.
And, in any case, there are arguments for the claim that we must assign probabilities to hypotheses like ‘The die lands on 1’ and ‘There will exist at least 10^16 people in the future.’ If we don’t assign probabilities, we are vulnerable to getting Dutch-booked and accuracy-dominated.
Suppose, then, that you accept that we must assign probabilities to the relevant hypotheses. Greaves and MacAskill’s point is that all reasonable-sounding probability assignments imply that we ought to pursue longtermist interventions (given that we accept their moral premise, which I discuss later). Consider, for example, the hypothesis that humanity spreads into space and that 10^24 people exist in the future. What probability assignment to this hypothesis sounds reasonable? Opinions will differ to some extent, but it seems extremely overconfident to assign this hypothesis a probability of less than one in one billion. On a standard view about the relationship between probabilities and rational action, that would imply a willingness to stake £1 billion on the hypothesis, losing it all if the hypothesis turns out true and winning an extra £2 if the hypothesis turns out false (assuming, for illustration’s sake only, that utility is linear with respect to money across this interval).
The case is the same with other empirical hypotheses that Greaves and MacAskill consider. To get the result that longtermist interventions don’t maximise expected value, you have to make all kinds of overconfident-sounding probability assignments, like ‘I am almost certain that humanity will not spread to the stars,’ ‘I am almost certain that smart, well-motivated people with billions of pounds of resources would not reduce extinction risk by even 0.00001%,’ ‘I am almost certain that billions of pounds of resources devoted to further research on longtermism would not unearth a viable longtermist intervention,’ etc. So, as it turns out, accepting longtermism does not commit us to strong claims about what the future will be like. Instead, it is denying longtermism that commits us to such claims.
So, to summarise the above, we have to assign probabilities to empirical hypotheses, on pain of getting Dutch-booked and accuracy-dominated. And all reasonable-seeming probability assignments imply that we should pursue longtermist interventions.
Now, this final sentence is conditional on the truth of Greaves and MacAskill’s moral premises. In particular, it depends on their claim that we ought to have a zero rate of pure time preference.
The first thing to note is that the word ‘pure’ is important here. As you point out, ‘we should be biased towards the present for the simple reason that tomorrow may not arrive.’ Greaves and MacAskill would agree. Longtermists incorporate this factor in their arguments, and it does not change their conclusions. Ord calls it ‘discounting for the catastrophe rate’ in The Precipice, and you can read more about the role it plays there.
When Greaves and MacAskill claim that we ought to have a zero rate of pure time preference, they are claiming that we ought not care less about consequences purely because they occur later in time. This pattern of caring really does seem indefensible. Suppose, for example, that a villain has set a time-bomb in an elementary school classroom. You initially think it is set to go off in a year’s time, and you are horrified. In a year’s time, 30 children will die. Suppose that the villain then tells you that they’ve set the bomb to go off in ten years’ time. In ten years’ time, 30 children will die. Are you now less horrified? If you had a positive rate of pure time preference, you would be. But that seems absurd.
As Ord points out, positive rates of pure time preference seem even less defensible when we consider longer time scales: ‘At a rate of pure time preference of 1 percent, a single death in 6,000 years’ time would be vastly more important than a billion deaths in 9,000 years. And King Tutankhamun would have been obliged to value a single day of suffering in the life of one of his contemporaries as more important than a lifetime of suffering for all 7.7 billion people alive today.’
Thanks again for the post! It’s good to see longtermism getting some critical examination.