All of ben_chugg&#x27;s Comments + Replies

Strong Longtermism, Irrefutability, and Moral Progress

Personally I think equating strong longtermism with longtermism is not really correct.

Agree! While I do have problems with (weak?) longtermism, this post is a criticism of strong longtermism :)

Strong Longtermism, Irrefutability, and Moral Progress

If you are agnostic about that, then you must also be agnostic about the value of GiveWell-type stuff

Why? GiveWell charities have developed theories about the effects of various interventions. The theories have been tested and, typically, found to be relatively robust. Of course, there is always more to know, and always ways we could improve the theories.

I don't see how this relates to not being able to develop a statistical estimate of the probability we go extinct tomorrow. (Of course, I can just give you a number and call it "my belief... (read more)

9[anonymous]3y

The benefits of GiveWell's charities are worked out as health or economic benefits which are realised in the future. e.g. AMF is meant to be good because it allows people who would have otherwise died to live for a few more years. If you are agnostic about whether everyone will go extinct tomorrow, then you must be agnostic about whether people will actually get these extra years of life.

Strong Longtermism, Irrefutability, and Moral Progress

Agree with almost all of this. This is why it was tricky to argue against, and also why I say (somewhere? podcast maybe?) that I'm not particularly worried about the current instantiation of longtermism, but what this kind of logic could justify.

I totally agree that most of the existential threats currently tackled by the EA community are real problems (nuclear threats, pandemics, climate change, etc).

I would note that the Greaves and MackAskill paper actually has a section putting forward 'advancing progress' as a plausible longter

... (read more)

JackM

Maybe (just maybe) we're getting somewhere here. I have no interest in adopting a 'problem/knowledge focused ethic'. That would seem to presuppose the intrinsic value of knowledge. I only think knowledge is instrumentally valuable insofar as it promotes welfare. Instead most EAs want to adopt an ethic that prioritises 'maximising welfare over the long-run'. Longtermism claims that the best way to do so is to actually focus on long-term effects, which may or may not require a focus on near-term knowledge creation - whether it does or not is essentially an empirical question. If it doesn't require it, then a strong longtermist shouldn’t consider a lack of knowledge creation to be a significant drawback.

ben_chugg3y4

I think I agree, but there's a lot smuggled into the phrase "perfect information on expected value". So much in fact that I'm not sure I can quite follow the thought experiment.

When I think of "perfect information on expected value", my first thought is something like a game of roulette. There's no uncertainty (about what can affect the system), only chance. We understand all the parameters of the system and can write down a model. To say something like this about the future means we would be basically omniscient - we would know wha... (read more)

weeatquince

Hi Ben. I agree with you. Yes I think roulette is a good analogy. And yes I think the "perfect information on expected value" is a strange claim to make. But I do think it is useful to think about what could be said and justified. I do think a claim along these lines could be made and it would not be wholly unfalsifiable and it would not require completely preferencing Bayesian expected value calculations. To give another analogy I think there is a reasonable long-termist equivalent of statements like: Because of differences in wealth and purchasing power we expect that a donor in the developed west can have a much bigger impact overseas than in their home country. So in practice looking towards those kinds of international development options is a useful tool to apply when we are deciding what to do. This does not completely exclude the probability that we can have impact locally with donations, but it does direct our searching. Being charitable to Will+Hillary, maybe that is all they are saying. And maybe it is so confusing because they have dressed it up in philosophical language – but this is because, as per GPI's goals, this paper is about engaging philosophy academics rather than producing any novel insight. (If being more critical I am not convinced that Will+Hillary successfully give sufficient evidence to make such a claim in this paper and also see my list of things their paper could improve above.)

Strong Longtermism, Irrefutability, and Moral Progress

Strong Longtermism, Irrefutability, and Moral Progress

There are non-measurable sets (unless you discard the axiom of choice, but then you'll run into some significant problems.) Indeed, the existence of non-measurable sets is the reason for so much of the measure-theoretic formalism.

If you're not taking a measure theoretic approach, and instead using propositions (which I guess, it should be assumed that you are, because this approach grounds Bayesianism), then using infinite sets (which clearly one would have to do if reasoning about all possible futures) leads to paradoxes. As E.T. Jaynes ... (read more)

MichaelStJules

This depends on the space. It's at least true for real-valued intervals with continuous measures, of course, but I think you're never going to ask for the measure of a non-measurable set in real-world applications, precisely because they require the axiom of choice to construct (at least for the real numbers, and I'd assume, by extension, any subset of any Rn), and no natural set you'll be interested in that comes up in an application will require the axiom of choice (more than dependant choice) to construct. I don't think the existence of non-measurable sets is viewed as a serious issue for applications. It is not true in a countable measure space (or, at least, you could always extend the measure to get this to hold), since assuming each singleton (like {x},x∈X) is measurable, every union of countably many singletons is measurable, and hence every subset is measurable (A=∪x∈A{x} is a countable union of singletons, A⊆X, X countable) . In particular, if you're just interested in the number of future people, assuming there are at most countably infinitely many (so setting aside the many-worlds interpretation of quantum mechanics for now), then your space is just the set of non-negative integers, which is countable. You could group outcomes to represent them with finite sets. Bayesians get to choose the measure spaces/propositions they're interested in. But again, I don't think dealing with infinite sets is so bad in applications.

Strong Longtermism, Irrefutability, and Moral Progress

What I meant by this was that I think you and Ben both seem to assume that strong longtermists don't want to work on near-term problems. I don't think this is a given (although it is of course fair to say that they're unlikely to only want to work on near-term problems).

Mostly agree here - this was the reason for some of the (perhaps cryptic) paragraphs in the Section "the Antithesis of Moral Progress." Longtermism erodes our ability to make progress to whatever extent it has us not working on real problems. And, to the extent that it does have us working ... (read more)

JackM

I don't necessarily see working on reducing extinction risk as wildly speculating about the far future. In many cases these extinction risks are actually thought to be current risks. The point is that if they happen they necessarily curtail the far future. I would note that the Greaves and MackAskill paper actually has a section putting forward 'advancing progress' as a plausible longtermist intervention! As I have mentioned this is only insofar as it will make the long-run future go well.

ben_chugg3y4

Thanks AGB, this is helpful.

I agree that longtermism is core part of the movement, and probably commands a larger share of adherents than I imply. However, I'm not sure to what extent strong longtermism is supported. My sense is that while most people agree with the general thrust of the philosophy, many would be uncomfortable with "ignoring the effects" of the near term, and remain focused on near-term problems. I didn't want to claim that a majority of EAs supported longtermism broadly-defined, but then only criticize a subset of those views.

I hadn't seen the results of the EA Survey - fascinating.

lukeprog

I know I'm late to the discussion, but… I agree with AGB's comment, but I would also like to add that strong longtermism seems like a moral perspective with much less "natural" appeal, and thus much less ultimate growth potential, than neartermist EA causes such as global poverty reduction or even animal welfare. For example, I'm a Program Officer in the longtermist part of Open Philanthropy, but >80% of my grantmaking dollars go to people who are not longtermists (who are nevertheless doing work I think is helpful for certain longtermist goals). Why? Because there are almost no longtermists anywhere in the world, and even fewer who happen to have the skills and interests that make them a fit for my particular grantmaking remit. Meanwhile, Open Philanthropy makes far more grants in neartermist causes (though this might change in the future), in part because there are tons of people who are excited about doing cost-effective things to help humans and animals who are alive and visibly suffering today, and not so many people who are excited about trying to help hypothetical people living millions of years in the future. Of course to some degree this is because longtermism is fairly new, though I would date it at least as far back as Bostrom's "Astronomical Waste" paper from 2003. I would also like to note that many people I speak to who identify (like me) as "primarily longtermist" have sympathy (like me) for something like "worldview diversification," given the deep uncertainties involved in the quest to help others as much as possible. So e.g. while I spend most of my own time on longtermism-motivated efforts, I also help out with other EA causes in various ways (e.g. this giant project on animal sentience), and I link to or talk positively about GiveWell top charities a lot, and I mostly avoid eating non-AWA meat, and so on… rather than treating these non-longtermist priorities as a rounding error. Of course some longtermists take a different approach than I do,

Strong Longtermism, Irrefutability, and Moral Progress

Strong Longtermism, Irrefutability, and Moral Progress

Thanks for the engagement!

I think you're mistaking Bayesian epistemology with Bayesian mathematics. Of course, no one denies Bayes' theorem. The question is: to what should it be applied? Bayesian epistemology holds that rationality consists in updating your beliefs in accordance with Bayes' theorem. As this LW post puts it:

Core tenet 3: We can use the concept of probability to measure our subjective belief in something. Furthermore, we can apply the mathematical laws regarding probability to choosing between different beliefs. If we want our b

ben_chugg3y3

I don't think the question makes sense. I agree with Vaden's argument that there's no well-defined measure over all possible futures.

MichaelStJules

There are definitely well-defined measures on any set (e.g. pick one atomic outcome to have probability 1 and the rest 0); there's just not only one, and picking exactly one would be arbitrary. But the same is true for any set of outcomes with at least two outcomes, including finite ones (or it's at least often arbitrary when there's not enough symmetry for equiprobability). For the question of how many people will exist in the future, you could use a Poisson distribution. That's well-defined, whether or not it's a reasonable distribution to use. Of course, trying to make your space more and more specific will run into feasibility issues.

5[anonymous]3y

Do you for example think there is a more than 50% chance that it is greater than 10 billion?

Strong Longtermism, Irrefutability, and Moral Progress

But we also have to make similar (although less strong) assumptions and have generalization error even with RCTs. Doesn't GiveWell make similar assumptions about the impacts of most of their recommended charities?

Yes, we do! And the strength of those assumptions is key. Our skepticism should rise in proportion to the number/feasibility of the assumptions. So you're definitely right, we should always be skeptical of social science research - indeed, any empirical research. We should be looking for hasty generalizations, gaps in the analysi... (read more)

ben_chugg3y0

Why are probabilities prior to action - why are they so fundamental? Could Andrew Wiles "rationally put probabilities" on him solving Fermat's Last Theorem? Does this mean he shouldn't have worked on it? Arguments do not have to be in number form.

Neel Nanda

To me, the fundamental point isn't probabilities, it's that you need to make a choice about what you do. If I have the option to give a $1mn grant to preventing nuclear war or give the grant to something else, then no matter what I do, I have made a choice. And so, I need to have a decision theory for making a choice here. And to me, subjective probabilities and Bayesian epistemology more generally, are by far the best decision theory I've come across for making choices under uncertainty. If there's a 1% chance of nuclear war, the grant is worth making, if there's a 10^-15 chance of nuclear war, the grant is not worth making. I need to make a decision, and so probabilities are fundamental, because they are my tool for making a decision. And there are a bunch of important question where we don't have data, and there's no reasonable way to get data (eg, nuclear war!). And any approach which rejects the ability to reason under uncertainty in situations like this, is essentially the decision theory of "never make speculative grants like this". And I think this is a clearly terrible decision theory (though I don't think you're actually arguing for this policy?)

[anonymous]3y24

If you refuse to claim that the chance of nuclear war up to 2100 is greater than 0.000000000001%, then I don't see how you could make a good case to work on it over some other possible intuitively trivial action, such as painting my wall blue. What would the argument be if you are completely agnostic as to whether it is a serious risk?

Strong Longtermism, Irrefutability, and Moral Progress

Strong Longtermism, Irrefutability, and Moral Progress

Sure - Nukes exist. They've been deployed before, and we know they have incredible destructive power. We know that many countries have them, and have threatened to use them. We know the protocols are in place for their use.

MichaelStJules3y13

To me this seems like you're making a rough model with a bunch of assumptions like that past use, threats and protocols increase the risks, but not saying by how much or putting confidences or estimates on anything (even ranges). Why not think the risks are too low to matter despite past use, threats and protocols?

Strong Longtermism, Irrefutability, and Moral Progress

Hi Michael!

It seems like you're acting as if you're confident that the number of people in the future is not huge, or that the interventions are otherwise not so impactful (or they do more harm than good), but I'm not sure you actually believe this. Do you?

I have no idea about the number of future people. And I think this is the only defensible position. Which interventions do you mean? My argument is that longtermism enables reasoning that de-prioritizes current problems in lieu of possible, highly uncertain, future problems. Focusing on such ... (read more)

MichaelStJules3y14

You refuse to commit to a belief about x, but commit to one about y and that's inconsistent.

I would rephrase as "You say you refuse to commit to a belief about x, but seem to act as if you've committed to a belief about x". Specifically, you say you have no idea about the number of future people, but it seems like you're saying we should act as if we believe it's not huge (in expectation). The argument for strong longtermism you're trying to undermine (assuming we get the chance of success and sign roughly accurate, which to me is more doubtful) goes throu... (read more)

Strong Longtermism, Irrefutability, and Moral Progress

Oh interesting. Did you read my critique as saying that the philosophy is wrong? (Not sarcastic; serious question.) I don't really even know what "wrong" would mean here, honestly. I think the reasoning is flawed and if taken seriously leads to bad consequences.

Owen Cotton-Barratt

I read your second critique as implicitly saying "there must be a mistake in the argument", whereas I'd have preferred it to say "the things that might be thought to follow from this argument are wrong (which could mean a mistake in the argument that's been laid out, or in how its consequences are being interpreted)".

ben_chugg3y4

Yeah I suppose I would still be skeptical of using ranges in the absence of data (you could just apply all my objections to the upper and low bounds of the range). But I'm definitely all for sensitivity analysis when there are data backing up the estimates!

Strong Longtermism, Irrefutability, and Moral Progress

Strong Longtermism, Irrefutability, and Moral Progress

I have read about (complex) cluelessness. I have a lot of respect for Hilary Greaves, but I don't think cluelessness is particularly illuminating concept. I view it as a variant of "we can't predict the future." So, naturally, if you ground your ethics in expected value calculations over the long term future then, well, there's going to be problems.

I would propose to resolve cluelessness as follows: Let's admit we can't predict the future. Our focus should instead be on error-correction. Our actions will have consequences - both intended and unintend... (read more)

JackM

I do think it's far more illuminating than "we can't predict the future". Really complex cluelessness is saying OK great you've carried out a CBA/CEA but you've omitted/ignored effects from the analysis that we: 1. Have good reason to expect will occur 2. Have good reason to suspect are sufficiently important such that they could change the sign of your final number if properly included in your analysis If the above factors are in fact true in the case of GiveWell (I think they probably are) then I don't think GiveWell CBAs are all that useful and the original point you were trying to make - that GiveWell analysis is obviously superior because it makes use of data - sort of breaks down because, quite simply, the data has a massive, gaping hole in it. This is not to criticise GiveWell in the slightest, it's just to acknowledge the monstrous task they're up against. Correct me if I'm wrong but what you seem to be arguing is that we're actually complexly clueless about everything, so we may as well just ignore the problem. I actually don't think this is true - we may be clueless about everything but not necessarily in a complex way. Consider the promotion of philosophy in schools, a class of interventions that I have written about. I'm not sure if these are definitely the best interventions (reception to my post was fairly lukewarm), but I also don't think we are complexly clueless about their effects in the same way that we are about the effects of distributing bednets. This is because it's just quite hard to think up reasons why it might be bad to promote philosophy in schools. Sure it could be the case that promoting philosophy in schools makes something bad happen, but I don't really have much of a reason to entertain that possibility if I can't think of a specific effect that fulfils the two factors I listed above. In the case of distributing bednets we are pretty certain there will be population effects, we are pretty certain these will be very significant

Strong Longtermism, Irrefutability, and Moral Progress

Hey Fin! Nice - lot's here. I'll respond to what I can. If I miss anything crucial just yell at me :) (BTW, also enjoying your podcast. Maybe we should have a podcast battle at some point ... you can defend longtermism's honour).

In any case: declaring that BE "has been refuted" seems unfairly rash.

Yep, this is fair. I'm imagining myself in the position of some random stranger outside of a fancy EA-gala, and trying to get people's attention. So yes - the language might be a little strong (although I do really think Bayesianism doesn't stand up t... (read more)

finm

Thanks for replying Ben, good stuff! Few thoughts. I'll concede that point! I think a better response to the one I originally gave was to point out that the case for strong longtermism relies on establishing a sensible lower(ish) bound for total future population. Greaves and MacAskill want to convince you that (say) at least a quadrillion lives could plausibly lie in the future. I'm curious if you have an issue with that weaker claim? I think your point about space exploration is absolutely right, and more than a nitpick. I would say two things: one is that I can imagine a world in which we could be confident that we would never colonise the stars (e.g. if the earth were more massive and we had 5 decades before the sun scorched us or something). Second, voicing support for the 'anything permitted by physics can become practically possible' camp indirectly supports an expectation of a large numbers of future lives, no? Hmm — to my lights Greaves and MacAskill are fairly clear about the differences between the two kinds of estimate. If your reply is that doing any kind of (toy) EV calculation with both estimates just implies that they're somehow "equally as capable of capturing something about reality", then it feels like you're begging the question. I don't understand what you mean here, which is partly my fault for being unclear in my original comment. Here's what I had in mind: suppose you've run a small-scale experiment and collected your data. You can generate a bunch of statistical scores indicating e.g. the effect size, plus the chance of getting the results you got assuming the null hypothesis was true (p-value). Crucially (and unsurprisingly) none of those scores directly give you the likelihood of an effect (or the 'true' anything else). If you have reason to expect a bias in the direction of positive results (e.g. publication bias), then your guess about how likely it is that you're picked up on a real effect may in fact be very different from any sta

JackM

I don't think this is true. Whenever Greaves and MacAskill carry out a longtermist EV calculation in the paper it seems clear to me that their aim is to illustrate a point rather than calculate a reliable EV of a longtermist intervention. Their world government EV calculation starts with the words "suppose that...". They also go on to say: This is the point they are trying to get across by doing the EV calculations.

Strong Longtermism, Irrefutability, and Moral Progress

I'm tempted to just concede this because we're very close to agreement here.

For example we need to wrestle with problems we face today to give us good enough feedback loops to make substantial progress, but by taking the long-term perspective we can improve our judgement about which of the nearer-term problems should be highest-priority.

If this turns out to be true (i.e., people end up working on actual problems and not, say, defunding the AMF to worry about "AI controlled police and armies"), then I have much less of a problem with longtermism... (read more)

Owen Cotton-Barratt

I think this is might be a case of the-devil-is-in-the-details. I'm in favour of people scanning the horizon for major problems whose negative impacts are not yet being felt, and letting that have some significant impact on which nearer-term problems they wrestle with. I think that a large proportion of things that longtermists are working on are problems that are at least partially or potentially within our foresight horizons. It sounds like maybe you think there is current work happening which is foreseeably of little value: if so I think it could be productive to debate the details of that.

ben_chugg3y0

Well, far be it from me to tell others how to spend their time, but I guess it depends on what the goal is. If the goal is to literally put a precise number (or range) on the probability of nuclear war before 2100, then yes, I think that's a fruitless and impossible endeavour. History is not an iid sequence of events. If there is such a war, it will be the result of complex geopolitical factors based on human belief, desires, and knowledge at the time. We cannot pretend to know what these will be. Even if you were to gather all the available ev... (read more)

[anonymous]3y10

You say that "there are good arguments for working on the threat of nuclear war". As I understand your argument, you also say we cannot rationally distinguish between the claim "the chance of nuclear war in the next 100 years is 0.00000001%" and the claim "the chance of nuclear war in the next 100 years is 1%". If you can't rationally put probabilities on the risk of nuclear war, why would you work on it?

MichaelStJules

But we also have to make similar (although less strong) assumptions and have generalization error even with RCTs. Doesn't GiveWell make similar assumptions about the impacts of most of their recommended charities? As far as I know, there are recent studies of GiveDirectly's effects, but the "recent" studies of the effects of the interventions of the other charities have probably had their samples chosen years ago, so their effects might not generalize to new locations. Where's the cutoff for your skepticism? Should we boycott the GiveWell-recommended charities whose ongoing intervention impacts of terminal value (lives saved, quality of life improvements) are not being measured rigorously in their new target areas, in favour of GiveDirectly? To illustrate the issue of generalization, GiveWell did a pretty arbitrary adjustment for El Niño for deworming, although I think this is the most suspect assumption I've seen them make. See Eva Vivalt's research on generalization (in the Causal Inference section) or her talk here.

MichaelStJules

Can you give some examples? I expect that someone could respond "That could be too unlikely to matter enough" to each of them, since we won't have good enough data.

Strong Longtermism, Irrefutability, and Moral Progress

Strong Longtermism, Irrefutability, and Moral Progress

Hi Owen!

Re: inoculation of criticism. Agreed that it doesn't make criticism impossible in every sense (otherwise my post wouldn't exist). But if one reasons with numbers only (i.e., EV reasoning), then longtermism becomes unavoidable. As soon as one adopts what I'm calling "Bayesian epistemology", then there's very little room to argue with it. One can retort: Well, yes, but there's very little room to argue with General Relativity, and that is a strength of the theory, not a weakness. But the difference is that GR is very precise: It's h... (read more)

Owen Cotton-Barratt3y12

Cool. I do think that trying to translate your position into the ontology used by Greaves+MacAskill it's sounding less like "longtermism is wrong" and more like "maybe longtermism is technically correct; who cares?; the practical advice people are hearing sucks".

I think that's a pretty interestingly different objection and if it's what you actually want to say it could be important to make sure that people don't hear it as "longtermism is wrong" (because that could lead them to looking at the wrong type of thing to try to refute you).

Strong Longtermism, Irrefutability, and Moral Progress

Hi Jack,

I think you're right, the comparison to astrology isn't entirely fair. But sometimes one has to stretch a little bit to make a point. And the point, I think, is important. Namely, that these estimates can be manipulated and changed all too easily to fit a narrative. Why not half a quadrillion, or 10 quadrillion people in the future?

On the falsifiability point - I agree that the claims are technically falsifiable. I struggled with the language for this reason while writing it (and Max Heitmann helpfully tried to make th... (read more)

JackM

Yes if you're happy to let your calculations be driven by very small probabilities of enormous value I suppose you're right that the great filter would never be conclusive. Whether or not it is reasonable to allow this is an open question in decision theory and I don't think it's something that all longtermists accept. The authors themselves don't appear to be all that comfortable with accepting it: This implies if they think a credence is miniscule or a long-lasting influence negligible that they might throw away the calculation.

JackM

The fact that they can be manipulated and changed doesn't strike me as much of a criticism. The more relevant question is if people actually do manipulate and change the estimates to fit their narrative. If they do we should call out these particular people, but even in this case I don't think it would be an argument against longtermism generally, just against the particular arguments these 'manipulaters' would put forward. The authors do at least set out their assumptions for the one quadrillion which they call their conservative estimate. For example, one input into the figure is an estimate that earth will likely be habitable for another 1 billion years, which is cited from another academic text. Now I'm not saying that their one quadrillion estimate is brilliantly thought through (I'm not saying it isn't either), I'm just countering a claim I think you're making that Greaves and MacAskill would likely add zeros or inflate this number if required to protect strong longtermism e.g. to maintain that their conservative longtermist EV calculation continues to beat GiveWell's cost-effectiveness calculation for AMF. I don't see evidence to suggest they would and I personally don't think they would manipulate in such a way. That's not to say that the one quadrillion figure may not change, but I would hope and would expect this to be for a better reason than "to save longtermism". To sum up I don't think your "amenable to drastic change" point is particularly relevant. What I do think is more relevant is that the one quadrillion estimate is slightly arbitrary, and I see this as a subtly different point. I may address this in a different comment.

ben_chugg3y3

Bob and Alice are at the bar, being served by Carol. Bob is trying to estimate whether Carol has children. He starts with a prior of 1/2. He then looks up the base rate of adults with children, and updates on that. Then he updates based on Carol's age. And wha... (read more)

james

Thanks for the reply and taking the time to explain your view to me :) I'm curious: My friend has been trying to estimate the liklihood of nuclear war before 2100. It seems like this is a question that is hard to get data on, or to run tests on. I'd be interested to know what you'd recommend them to do? Is there a way I can tell them to approach the question such that it relies on 'subjective estimates' less and 'estimates derived from actual data' more? Or is it that you think they should drop the research question and do something else with their time, since any approach to the question would rely on subjective probability estimates that are basically useless?

Strong Longtermism, Irrefutability, and Moral Progress

A case against strong longtermism

Hey James!

Answering this in its entirety would take a few more essays, but my short answer is: When there are no data available, I think subjective probability estimates are basically useless, and do not help in generating knowledge.

I emphasize the condition when there are no data available because data is what allows us to discriminate between different models. And when data is available, well, estimates become less subjective.

Now, I should say that I don't really care what's "reasonable" for someone to do - I definitely don't want... (read more)

ben_chugg

As a major aside - there's a little joke Vaden and I tell on the podcast sometimes when talking about Bayesianism vs Criticial Rationalism (an alternative philosophy first developed by Karl Popper). The joke is most certainly a strawman of Bayesianism, but I think it gets the point across. Bob and Alice are at the bar, being served by Carol. Bob is trying to estimate whether Carol has children. He starts with a prior of 1/2. He then looks up the base rate of adults with children, and updates on that. Then he updates based on Carol's age. And what car she drives. And the fact that she's married. And so on. He pulls out a napkin, does some complex math, and arrives at the following conclusion: It's 64.745% likely that Carol has children. Bob is proud of his achievement and shows the napkin to Alice. Alice leans over the bar and asks "Hey Carol - do you have kids?". Now, obviously this is not how the Bayesian acts in real life. But it demonstrates the care the Bayesian takes in having correct beliefs; about having the optimal brain state. I think this is the wrong target. Instead, we should be seeking to falsify as many conjectures as possible, regardless of where the conjectures came from. I don't care what Alice thought the probability was before she asked the question, only about the result of the test.