Epistemics: (Part 6: Extraordinary claims require extraordinary evidence)

There have been over 100K UFO sightings reported worldwide since 1940. Roughly 5% or so are “strong” events, which seem rather hard to explain due to either many witnesses, especially reliable witnesses, physical evidence, or other factors … I have been tempted to learn about many of these strong dramatic events. (Eg) Which I now somewhat regret, as I now find myself the awkward position of having made an awkward inference …  I’m stuck with putting substantial weight on explanations #3 [“real amazing devices/organisms from secret groups on Earth”, or] #4 [“real amazing devices/organisms from secret groups beyond Earth”] for at least some of the thousand-plus strong dramatic UFO events. Which feels pretty awkward. 

Robin Hanson, “My awkward inference
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1. Introduction

This is Part 6 in my series on epistemics: practices that shape knowledge, belief and opinion within a community. In this series, I focus on areas where community epistemics could be productively improved.

Part 1 introduced the series and briefly discussed the role of funding, publication practices, expertise and deference within the effective altruist ecosystem.

Part 2 discussed the role of examples within discourse by effective altruists, focusing on the cases of Aum Shinrikyo and the Biological Weapons Convention.

Part 3 looked at the role of peer review within the effective altruism movement.

Part 4 looked at the declining role of cost-effectiveness analysis within the effective altruism movement. Part 5 continued that discussion by explaining the value of cost-effectiveness analysis.

Today’s post begins from a simple observation. Effective altruists make a number of claims that most observers regard as extraordinary. These include existential risk pessimism, the claim that humanity currently faces very high levels of existential risk; the time of perils hypothesis that levels of existential risk may soon drop by many orders of magnitude; and ambitious growth expectations in many areas, such as artificial intelligence and gross world product.

As Carl Sagan reminds us, extraordinary claims require extraordinary evidence. If effective altruists want to defend extraordinary claims, it is not enough to show that these claims are physically possible, that they fail to be ruled out by our current evidence, or that they are supported by a few suggestive considerations. Effective altruists owe us many excellent reasons to believe extraordinary claims.

In practice, extraordinary claims are sometimes supported by rather less than extraordinary evidence. Today’s post looks at two examples of extraordinary claims made on the basis of thin evidence, as a way to illustrate the importance of supporting extraordinary claims with extraordinary evidence.

2. UFO sightings

Robin Hanson is an associate professor of economics at George Mason University and a research associate at the Future of Humanity Institute. Hanson’s blog, Overcoming bias, was originally shared among a number of authors, most prominently Hanson and Eliezer Yudkowsky. The blog aims to “move our beliefs closer to reality, in the face of our natural biases such as overconfidence and wishful thinking”. That is an admirable goal. I am not sure that Hanson’s goal is always achieved.

Hanson is known, among other things, for his “Grabby aliens” thesis that expansive, “grabby” alien civilizations now control about half of the universe. That is already quite a claim, but I want to begin today with a much more striking claim that Hanson makes: aliens not only exist, but also quite possibly lie behind a number of recently claimed UFO sightings.

Hanson writes on his blog:

There have been over 100K UFO sightings reported worldwide since 1940. Roughly 5% or so are “strong” events, which seem rather hard to explain due to either many witnesses, especially reliable witnesses, physical evidence, or other factors. Many of these events are also “dramatic”, wherein the UFOs seem to display amazing abilities, ones well beyond those held by any known Earth orgs. I’d guess there are at least a thousand such strong dramatic reported events.

What is the most natural explanation for such events? Traditionally, they are explained in the same way as encounters with witches, ghosts, and Bigfoot: as misperceptions, as poor inferences, and as psychological conditions latching on to existing cultural narratives. More rarely, they are explained as the result of cheap hoaxes. But Hanson is not so sure about either of these explanations.

Hanson lists four possible explanations for “strong dramatic” sightings.

  1. observers fooled by error/mistakes/hallucinations,
  2. people lying or observers fooled by purposeful hoaxes,
  3. real amazing devices/organisms from secret groups on Earth, or
  4. real amazing devices/organisms from secret groups beyond Earth.

Hanson argues that we should place substantial credence in the falsity of (1) and (2), concluding that “I’m stuck with putting substantial weight on explanations #3,4 for at least some of the thousand-plus strong dramatic UFO events.”

That is an extraordinary claim, and it should be supported by extraordinary evidence. A good place to start would be saying what is wrong with (1), which as we saw is the typical explanation for a wide variety of paranormal beliefs. Surely Hanson gives a strong, novel argument against (1)?

That is not what Hanson does. Here is the entirety of Hanson’s argument against (1):

It seems clear to me that #1 can only plausibly explain a modest fraction of strong dramatic events. Most errors would have to be much closer to gross incompetence than to “oops”. (If you’ve also looked but can’t see this, I just don’t know what to say. Pay more attention?)

If there is an argument in this passage, I cannot find it. Hanson asserts without argument that (1) cannot play its usual role, unless the following is to count as an argument: “If you’ve also looked but can’t see this, I don’t know what to say. Pay more attention?”.

What about (2)? For the most part, I think we should say the same thing here that we would say in the case of any other paranormal belief: (2) is a good explanation for only a small number of cases, the vast majority of which are explained by (1). Here Hanson nails it:

In order to explain most strong dramatic events this way, I just don’t think it works to postulate scattered amateur liars and hoaxers. Instead I think one needs a big conspiracy, wherein a coalition of orgs has secretly and professionally coordinated to spend big budgets over many decades to have many lie, and to fool others via what are essentially magic tricks.

As Hanson notes, even conspiracies involving, for example, the entire US government would be unable to do the trick, since reports of UFO sightings occur across the globe, including in countries largely closed to the United States, such as the USSR during the Cold War. That’s why most people lean on (1) most of the time. If we dismiss (1) without argument, then we are led, without argument, to the extraordinary claims (3) and (4), unless we buy a version of (2) that is so inflated that only the most ardent conspiracy theorist would even consider it.

(3) and (4) are extraordinary claims, so they should be supported by extraordinary evidence, whereas Hanson hasn’t provided any credible evidence for (3) and (4). This means that we should not give serious credence to (3) or (4).

One way to test the robustness of Hanson’s reasoning is to ask how Hanson rules out sightings of ghosts, witches, Bigfoot and the like, while retaining substantial credence in the genuineness of some recent UFO sightings. What relevant difference is there to mark out UFO sightings as deserving of serious credence while investing no significant credence in Bigfoot, ghosts and witches? I wish I could report that Hanson offers an argument for his views here, but Hanson appears to give us no more than bare assertion:

I should mention that I’ve also looked at the best evidence offered for angels, ghosts, and fairies, and those just look much worse to me. The best evidence for ball lightning in the field is also pretty bad, even though the usual consensus believes in that due to it being created in the lab.

I don’t know how to express my disappointment at this type of reasoning strongly enough to convey my feelings. Extraordinary claims need extraordinary evidence. They do not need bluster, assertion, or Hanson’s repeated insinuations throughout this article that UFO sightings are something “elites” don’t want you to know about. These dialectical moves have nothing to do with reason and evidence, and are more likely to reinforce bias than they are to overcome it.

3. Modest epistemology and the Bank of Japan

Eliezer Yudkowsky is co-founder of the Machine Intelligence Research Institute. Yudkowsky is among the most influential members of the rationalist community and is widely read and cited by effective altruists.

Yudkowsky is known for confident and extreme predictions, many of which turn out to be wrong. One case in particular may illustrate the need to provide stronger evidence in support of extraordinary claims.

In his book, Inadequate equilibria, Eliezer Yudkowsky argues against what he calls modest epistemology, which holds “that we should be very hesitant to take our own reasoning at face value in the face of novelty or disagreement”.

Yudkowsky opposes modest epistemology to the claim of this post, that extraordinary claims require extraordinary evidence. To paint this contrast, Yudkowsky cites the software developer Hal Finney as holding:

If we accept the principle that “extraordinary claims require extraordinary evidence”, we should demand a high degree of justification for departing from the majority view. The mere fact that our own opinion seems sound would not be enough.

Yudkowsky disagrees. To illustrate his view, Yudkowsky cites a footnote from his paper, “Intelligence explosion microeconomics,” in which he criticizes the monetary policy of the Bank of Japan for being too tight.

Doubling down on this criticism, Yudkowsky claims that prior to the tenure of Haruhiko Kuroda at the head of the Bank of Japan, “Japan’s monetary policy was utterly deranged”, costing the country trillions of dollars.

This is an extraordinary claim, and it is natural to think that such claims should require extraordinary evidence. Here many readers may find themselves nodding in agreement with Yudkowsky’s summary of the modest perspective (which he himself does not endorse):

How likely is it that an entire country—one of the world’s most advanced countries—would forego trillions of dollars of real economic growth because their monetary controllers—not politicians, but appointees from the professional elite—were doing something so wrong that even a non-professional could tell? How likely is it that a non-professional could not just suspect that the Bank of Japan was doing something badly wrong, but be confident in that assessment? … Surely some humility is appropriate when criticizing the elite decision-makers governing the Bank of Japan. What if it’s you, and not the professional economists making these decisions, who have failed to grasp the relevant economic considerations?

Yudkowsky does not adopt the modest perspective. He holds that by reading blogs about economic policy, he was justified in becoming highly confident that the Bank of Japan was wrong. Yudkowsky expresses this opinion through an imagined dialogue with a skeptical economist:

CONVENTIONAL CYNICAL ECONOMIST: So, Eliezer, you think you know better than the Bank of Japan and many other central banks around the world, do you?

ELIEZER:  Yep. Or rather, by reading econblogs, I believe myself to have identified which econbloggers know better, like Scott Sumner.

C.C.E.: Even though literally trillions of dollars of real value are at stake?


This isn’t a good start. While it is certainly possible for central banks to err, for a non-economist to place high confidence in the claim that a leading central bank is making a trillion-dollar mistake requires a good deal evidence than a glance at an economics blog is likely to provide.

In Inadequate equilibria, Yudkowsky now claims that he was right, and thinks it is so clear that he was right that he uses this example to illustrate the pitfalls of modest epistemology.

Why does Yudkowsky think that he was right? The only evidence we are provided is a temporal correlation between a change in monetary policy and a rise in Real GDP. Yudkowsky writes:

When we critique a government, we don’t usually get to see what would actually happen if the government took our advice. But in this one case, less than a month after my exchange with John, the Bank of Japan—under the new leadership of Haruhiko Kuroda, and under unprecedented pressure from recently elected Prime Minister Shinzo Abe, who included monetary policy in his campaign platform—embarked on an attempt to print huge amounts of money, with a stated goal of doubling the Japanese money supply. Immediately after, Japan experienced real GDP growth of 2.3%, where the previous trend was for falling RGDP. Their economy was operating that far under capacity due to lack of money.

Now, Yudkowsky may have been right that the Bank of Japan was leaving money on the table. But it’s not so clear that he was right, and demonstrating this certainly requires a good deal more than a few sentences about real GDP trends.

The importance of providing more evidence for such an extraordinary claim is nicely illustrated by Matthew Barnett. Explaining macroeconomic changes is a difficult business, and while it is certainly true that Japan did see real GDP growth in the neighborhood of 2% in the year that Haruhiko Kuroda assumed leadership of the bank of Japan, it’s not at all obvious that looser monetary policy explains this change. Barnett writes:

According to official government data, Japan’s RGDP had not been falling prior to 2013, other than the fall caused by the Great Recession. RGDP did grow by ~2.0% in 2013, but I cannot discern any significant change in the trend after Haruhiko Kuroda began serving as governor at the Bank of Japan.

Why might we demand more evidence to attribute Japan’s Real GDP growth in 2013 to the monetary policy changes imposed by Haruhiko Kuroda? Well, as Barnett explains, there doesn’t seem to be any obvious change in the growth trajectory after Kuroda was appointed. For example, Barnett cites the following figure:

Without more evidence, this trend doesn’t provide any reason to attribute Japan’s real GDP growth in 2013 to changes in monetary policy.

In support of his claim, Yudkowsky cites a Washington Post article from 2017 taking a retrospective look at Japan’s change in monetary policy. This isn’t a great start at providing extraordinary evidence – while the Washington Post is among the more reliable newspapers in circulation today, it’s usually best to prefer substantive academic research over a newspaper article written by a reporter with a BA in History.

More to the point, as Barnett notes, this article actually says nothing about real GDP, the quantity which Yudkowsky is concerned with. Instead, it focuses on labor market improvements.

It is true that Japan experienced falling unemployment after the tenure of Karoda, but again, Barnett notes, it’s not so clear that this trend was due to a change in monetary policy. In this figure, provided by Barnett, there is no discernible change in the rate of falling unemployment after the appointment of Karoda.

Moreover, even if Yudkowsky was right in his criticism of the Bank of Japan’s monetary policy, there is very little evidence for his extraordinary claim that failed monetary policy cost Japan literally trillions of dollars. Even Scott Sumner, the economics blogger cited by Yudkowsky in support of this claim, throws Yudkowsky under the bus, writing:

I certainly believe the BOJ policy had the effect of boosting Japan’s real GDP, but the figure cited by Yudkowsky (“trillions of dollars”) seems excessive.

Summing up, what appears to have happened is that Yudkowsky asserted in a footnote that Japan’s monetary policy was too tight. He subsequently, after receiving apparently confirmatory evidence, asserted that Japan had lost trillions of dollars in Real GDP due to its pre-2013 monetary policy. Yudkowsky made this extraordinary claim despite having no serious background in economics, basing his claim primarily on the perusal of at least one economics blog. Yudkowsky subsequently cited as evidence of his claim a Washington Post article by a reporter with a BA in history, which provided little support for Yudkowsky’s claim.

It is not crazy to think that governments’ economic policies can be wrong, even sometimes badly wrong. But to assert with high confidence that governments are leaving trillions of dollars on the table requires extraordinary evidence, and Yudkowsky does not appear to have been in possession of anything like the requisite evidence before, or after making this assertion. Even the chief expert cited by Yudkowsky has thrown him under the bus here, as has the forum he helped to found (LessWrong).

Nevertheless, Yudkowsky thinks that he was not only right in his claims, but so clearly right that he uses his claims as the first of two illustrations for his opposition to epistemic modesty. For my part, I count this episode as a good illustration of the value of epistemic modesty.

4. Conclusion

In this post, I suggested that extraordinary claims require extraordinary evidence. Because extraordinary claims are themselves unlikely, anything less than extraordinary evidence cannot lend significant probability to extraordinary claims.

I discussed two areas in which prominent figures associated with the effective altruism movement have made extraordinary claims on rather less than extraordinary evidence. In Section 2, we saw that Robin Hanson asserts on very little evidence that some UFO sightings are likely to be genuine. In Section 3, we saw that Yudkowsky asserts, again on quite thin evidence, that the Bank of Japan’s monetary policy prior to the tenure of Haruhiko Kuroda cost Japan trillions of dollars.

We also saw some concerning attacks on the need to support extraordinary claims with extraordinary evidence. We saw that Yudkowsky directly criticizes the requirement to support extraordinary claims with extraordinary evidence as a tenant of “modest epistemology”. We saw that Yudkowsky makes the striking decision to illustrate the virtues of his alternative epistemological approach by using extraordinary and largely unevidenced claims that he had previously made about Japanese monetary policy, claims which even the friendliest experts have publicly condemned as extreme.

I suspect many readers will agree that Hanson and Yudkowsky went too far. Extraordinary claims need to be supported by extraordinary evidence. When they are not, discussions go off the rails.

Now, please take a moment to reflect on some other claims made by effective altruists. These might include the examples introduced at the beginning of this post: existential risk pessimism, the claim that humanity currently faces very high levels of existential risk; the time of perils hypothesis that levels of existential risk may soon drop by many orders of magnitude; and ambitious growth expectations in many areas, such as artificial intelligence and gross world product.

Are these and similar claims supported by extraordinary evidence? If so, I would like to see that evidence. If not, on what rational basis are these claims given nontrivial, even high credence by large numbers of effective altruists?


4 responses to “Epistemics: (Part 6: Extraordinary claims require extraordinary evidence)”


    I think you are here conflating claims that can be plausibly attributed to the EA community with random individuals who have some association with the community, so it seems a bit unfair on the EA community. This seems a bit like questioning the epistemics of climate scientists by picking out crazy things that individual climate scientists have said.

    For the reasons you mention, I agree that Hanson’s claims about UFOs are very implausible. But I’m not sure Hanson would class himself as an EA. If he is, I would guess that the number of EAs who endorse his claims about UFOs is exactly 1, and that person is Robin Hanson. I’ve never seen another EA endorse these claims and they are just not a focus of the community in any respect.

    Yudkowsky’s claims about the Japanese central bank also seem to be idiosyncratic to Eliezer, with almost all EAs never having thought about the topic or mentioned it. Indeed, insofar as EAs/rationalists have talked about it, it seems to have been to strongly criticise Eliezer. e.g. Barnett’s Lesswrong post that you cite has a lot of upvotes and the comments seem to be generally supportive of Barnett. There was another post criticising Eliezer’s epistemics that had to be edited for aggressive tone. https://forum.effectivealtruism.org/posts/ZS9GDsBtWJMDEyFXh/eliezer-yudkowsky-is-frequently-confidently-egregiously

    1. David Thorstad Avatar

      Thanks John!

      I do not attribute either of the claims discussed in this post to the EA community at large. It would be a major argumentative error to pick claims held by the community at large to use as examples in this post. After all, I am looking to find examples that my readers will judge to be both (a) extraordinary claims and (b) supported by less than extraordinary evidence.

      The odd thing about extraordinary claims is that everyone tends to think that their own claims are both (a) not extraordinary and (b) supported by excellent evidence, even when most outside observers would disagree. So for example, if I had written about the Time of Perils Hypothesis, I expect I would be told that the claim is quite plausible on its face and that it is supported by many strong arguments.

      I hope that in thinking through how thinkers such as Yudkowsky and Hanson can be led into making extraordinary claims on the basis of rather less than extraordinary evidence, readers might be led to reflect on whether they might be vulnerable to some of the same mistakes.

      At the same time, although Yudkowsky and Hanson are not speaking for the EA community, I do not think it is fair to describe them as “random individuals who have some association with the community.” As you know, both individuals have very strong associations with the EA community, and their writings are among the primary sources through which many individuals found their way into the community. Institutes such as MIRI and blogs or fora such as LessWrong and Overcoming Bias continue to be widely engaged with, read and cited by effective altruists.

      I link to the post that you mentioned at the start of my discussion of Eliezer Yudkowsky. There may well be issues of tone, but the content of that post is very important and at least in broad outline, probably correct. I was happy to see that post being written and reasonably well-received. It is a good sign when a community takes steps to make sure that extraordinary claims within the community are being made on the basis of appropriately strong evidence. This is something I would like to see more of in years to come.

  2. Vasco Grilo Avatar
    Vasco Grilo

    Thanks for the post, David! For a stronger case for UFOs, you may want to check Magnus Vinding’s 2 posts:

    1. David Thorstad Avatar

      Thanks Vasco!

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