[Linkpost] Can we confidently dismiss the existence of near aliens? Probabilities and implications

Thanks for your comment. I basically agree, but I would stress two points.

First, I'd reiterate that the main conclusions of the post I shared do not rest on the claim that extraordinary UFOs are real. Even assuming that our observed evidence involves no truly remarkable UFOs whatsoever, a probability of >1 in 1,000 in near aliens still looks reasonable (e.g. in light of the info gain motive), and thus the possibility still seems (at least weakly) decision-relevant. Or so my line of argumentation suggests.

Second, while I agree that the wild abilities are a reason to update toward thinking that the reported UFOs are not real objects, I also think there are reasons that significantly dampen the magnitude of this update. First, there is the point that we should (arguably) not be highly confident about what kinds of abilities an advanced civilization that is millions of years ahead of us might possess. Second, there is the point that some of the incidents (including the famous 2004 Nimitz incident) involve not only radar tracking (as reported by Kevin Day in the Nimitz incident), but also eye-witness reports (e.g. by David Fravor and Alex Dietrich in the case of Nimitz), and advanced infrared camera (FLIR) footage (shot by Chad Underwood during Nimitz). That diversity of witnesses and sources of evidence seems difficult to square with the notion that the reported objects weren't physically real (which, of course, isn't to say that they definitely were real).

When taking these dampening considerations into account, it doesn't seem to me that we have that strong reason to rule out that the reported objects could be physically real. (But again, the main arguments of the post I shared don't hinge on any particular interpretation of UFO data.)

I think this almost perfectly describes my problem with these videos/accounts/sensor readings. The same thing that makes them better evidence of aliens also makes them less likely to be real evidence. The crazier the physical constraints, the more likely "if this is real, the explanation is extra-terrestrial" becomes, but the less likely "it is real" becomes. Evidence that significantly increases the probability of  "this is real" without significantly decreasing the probability of "if this is real, the explanation is extra-terrestrial" seems necessary yet elusive.

The discussion of UAPs lately reminds me of the "How would Magnus Carlsen beat me at chess?" example that is popular in alignment these days. The still-unexplained phenomena that people will demand explanations for must be rare and hard to explain without a lot of good observations, or they wouldn't still be unexplained.

It seems similar to assuming that dark matter must be far more mysterious than just a particle, because we have so much trouble confirming any explanation of it, despite the fact that its observed behavior tells us that it should be extremely hard to confirm for any methods available to us.

I think the fact that the accelerations are close to, but not, a complete violation of physics is the most interesting, but it depends on how likely you think it is that a non-extraterrestrial explanation for a rare phenomena would also not seem to violate those laws. Or how likely a non-extraterrestrial explanation might be to appear to violate the laws of physics before further investigation. I do think this actually would make me update a bit in favor of extra-terrestrials if I thought about it more.

I wish my thoughts on this were better formulated, but I've been avoidant of UAP stuff for a while because engaging with it usually left me very frustrated and annoyed, and I don't think it's something we are likely to make meaningful progress on.

Thanks! :)

Assigning a single number to such a prior, as if it means anything, seems utterly absurd.

I don't agree that it's meaningless or absurd. A straightforward meaning of the number is "my subjective probability estimate if I had to put a number on it" — and I'd agree that one shouldn't take it for more than that.

I also don't think it's useless, since numbers like these can at least help give a very rough quantitative representation of beliefs (as imperfectly estimated from the inside), which can in turn allow subjective ballpark updates based on explicit calculations. I agree that such simple estimates and calculations should not necessarily be given much weight, let alone dictate our thinking, but I still think they can provide some useful information and provoke further thought. I think they can add to purely qualitative reasoning, even if there are more refined quantitative approaches that are better still.

You give a prior of 1 in a hundred that aliens have a presence on earth. Where did this number come from?

It was in large part based on the considerations reviewed in the section "I. An extremely low prior in near aliens". The following sub-section provides a summary with some attempted sanity checks and qualifications (in addition to the general qualifications made at the outset):

All-things-considered probability estimates: Priors on near aliens

Where do all these considerations leave us? In my view, they overall suggest a fairly ignorant prior. Specifically, in light of the (interrelated) panspermia, pseudo-panspermia, and large-scale Goldilocks hypotheses, as well as the possibility of near aliens originating from another galaxy, I might assign something like a 10 percent prior probability to the existence of at least one advanced alien civilization that could have reached us by now if it had decided to. (Note that I am here using the word “civilization” in a rather liberal sense; for example, a distributed web of highly advanced probes would count as a civilization in this context.) Furthermore, I might assign a probability not too far from that — maybe around 1 percent — to the possibility that any such civilization currently has a presence around Earth (again, as a prior).

Why do I have something like a 10 percent prior on there being an alien presence around Earth conditional on the existence of at least one advanced alien civilization that could have reached us? In short, the main reason is the info gain motive that I explore at greater length below. Moreover, as a sanity check on this conditional probability, we can ask how likely it is that humanity would send and maintain probes around other life-supporting planets assuming that we became technologically capable of doing this; roughly 10 percent seems quite sane to me.

At an intuitive level, I would agree with critics who object that a ~1 percent prior probability in any kind of alien presence around Earth seems extremely high. However, on reflection, I think the basic premises that get me to this estimate look quite reasonable, namely the two conjunctive 10-percent probabilities in “the existence of at least one advanced alien civilization that could have reached us by now if it had decided to” and “an alien presence around Earth conditional on the existence of at least one advanced alien civilization that could have reached us”.

Note also that there are others who seem to defend considerably higher priors regarding near aliens (see e.g. these comments by Jacob Cannell; I agree with some of the points Cannell makes, though I would frame them in more uncertain and probabilistic terms).

I can see how substantially lower priors than mine could be defensible, even a few orders of magnitude lower, depending on how one weighs the relevant arguments. Yet I have a hard time seeing how one could defend an extremely low prior that practically rules out the existence of near aliens. (Robin Hanson has likewise argued against an extremely low prior in near aliens.)