Dark Forest Theories

"Sufficiently advanced" tech could also plausibly identify all those hidden civilizations. For example, an underground civilization would produce unusual seismic activity, and taking up some inner portion of a gas giant or star would alter their outward behavior. Ultimately, civilizations use mass-energy in unnatural ways, and I don't see a fundamental physical principle that could protect that from all possible sensing. 

More importantly, I don't think your suggestions address my point that hostile civilizations would get you before you even evolve.

But, let's grant that you're the first civilization to evolve in your galaxy, or at the least among the first before someone starts sending out probes to prevent any new civilizations from arising and threatening them. And let's grant that they will never find you. That is a victory, in that you survive. But the costs are astronomical: you only get to use the mass-energy of a single planet, or star, or Oort Cloud, while someone else gets the entire galaxy.

To put it another way: mass-energy is required for your civilization to exist and fulfill its preferences, so far as we understand the universe. If you redirect any substantial amount of mass-energy away from its natural uses (stars, planets, asteroids), that's going to be proportionally detectable. So, you can only hide by strangling your own civilization in its crib. Not everyone is going to do that; I seriously doubt that humanity (or any artificial descendant) will, for one.

(This comes back to my link about "no stealth in space" - the phrase is most commonly invoked when referring to starships. If your starship is at CMB temperatures and never moves, then yeah, it'd be hard to detect. But also you couldn't live in it, and it couldn't go anywhere! You want your starship—your civilization—to actually do something, and doing work (in a physics sense) is detectable.)

The problem with Dark Forest theory is that, in the absence of FTL detection/communication, it requires a very high density and absurdly high proportion of hiding civilizations. Without that, expansionary civilizations dominate. The only known civilization, us, is expansionary for reasons that don't seem path-determinant, so it seems unlikely that the preconditions for Dark Forest theory exist.

To explain:

Hiders have limited space and mass-energy to work with. An expansionary civilization, once in its technological phase, can spread to thousands of star systems in mere thousands of years and become unstoppable by hiders. So, hiders need to kill expansionists before that happens. But if they're going to hide in their home system, they can't detect anything faster than FTL! So you need murderous hiding civs within at least a thousand light years of every single habitable planet in the galaxy, all of which need to have evolved before any expansionary civs in the area. This is improbable unless basically every civ is a murderous hider. The fact that the only known civ is not a murderous hider, for generalizable reasons, is thus evidence against the Dark Forest theory.

Potential objections:

• Hider civs would send out stealth probes everywhere.

Still governed by FTL, expansionary civ would become overwhelmingly strong before probes reported back.

• Hider civs would send out killer probes everywhere.

If the probes succeed in killing everything in the galaxy before they reach the stars, you didn't need to hide in the first place. (Also, note that hiding is a failed strategy for everyone else in this scenario, you can't do anything about a killer probe when you're the equivalent of the Han dynasty. Or the equivalent of a dinosaur.) If the probes fail, the civ they failed against will have no reason to hide, having been already discovered, and so will expand and dominate. 

• Hider civs would become so advanced that they could hide indefinitely from expansionary civs, possibly by retreating to another dimension.

Conceivable, but I'd rather be the expansionary civs here?

• Hider civs would become so advanced that they could kill any later expansionary civ that controlled thousands of star systems.

I think this is the strongest objection. If, for example, a hider civ could send out a few ships that can travel at a higher percentage of lightspeed than anything the expansionary civ can do, and those ships can detonate stars or something, and catching up to this tech would take millions of years, then just a few ships could track down and obliterate the expansionary civ within thousands/tens of thousands of years and win.

The problem is that the "hider civ evolved substantially earlier" part has to be true everywhere in the galaxy, or else somewhere an expansionary civilization wins and then snowballs with their resource advantages - this comes back to the "very high density and absurdly high proportion of hiding civilizations" requirement. The hiding civs have to always be the oldest whenever they meet an expansionary civ, and older to a degree that the expansionary civ's likely several orders of magnitude more resources and population doesn't counteract the age difference.

Best partners get married young; people who can't keep a relationship are always looking for someone new.

This is why I was always puzzled why Tinder, or other dating apps, became so popular. 

Isn't using it a clear signal that no one in the user's friend/acquaintance groups desires to date them?

And that if they are on it for more then a few days, that they are less desirable partners?

There seems to be a negative feedback loop to scale instead of positive.  

I don't think this is an adequate account of the selection effects we find in the job market. Consider:

• We don't expect people to disappear from the job market just because they're the best. They disappear from the market when they've found a match, so that they and their counterpart become confident in the relationship's durability and shift from explore to exploit, investing in the relationship for the long term. The pool of candidates is comprised both of those who outgrew their previous position or relationship, and those who got fired or dumped. Insofar as the market suffers from information asymmetries or different rates of performance growth between partners, we should expect lots of participation in the market by high-quality people seeking to move up from a previous mismatch with a low-quality partner.
• Low-quality employees get discouraged and exit the job market in their field, while low-quality businesses go bankrupt. The people who aren't dating include both those who are in relationships (which only means they're well-matched and better than no partner at all) and those who are too stressed or unhealthy or discouraged to even try to date. Participating in the market is a costly signal that you consider yourself hireable/dateable or are successful and ready to grow.
• Searching widely for the next job may be a sign of vigor and open-mindedness - the people putting out the most applications are those most determined to succeed.

One factor that is discouraging to consider is how switching costs and the cost of participation in the market intersect.

• If it's cheap to look for a partner, costly to break up, and a lot of information asymmetry, then there'll always be a set of terrible partners who are always on the hunt (because it's cheap), who have a real chance of finding a better match (because of information asymmetry), and who can expect to keep the good match around for a while (because of high switching costs). The US military is an example. It has a massive advertising budget and a huge manpower shortage, so it's always on the hunt for recruits. There's a big difference between its heroic and self-actualizing self-portrayal and the dismal and dehumanizing experience many soldiers report. And once you're in, you can't just leave. The existence of these entities in any market with these properties is a discouraging sign when considering candidate jobs/partners at random. If you find that participation in the market is cheap or that sharing negative information about a candidate is discouraged (i.e. a powerful politician who could retaliate against anyone accusing them of wrongdoing), then learning this information should make you downgrade your expectations of the candidate's quality.

That being said, it may be that seeking a job via responding to job applications online is a sign of a lower-tier candidate, all else equal. Whether a writer submits to editors independently or via an agent may say a lot about the writer's quality, and whether a first date comes from an app, a recommendation from a friend, or flirtation at a party might say a lot about the potential romantic partner.

(we should greatly improve the ratio of good things, also.)

popular culture is full of stories of genius scientists, engineers, politicians, military leaders, entrepreneurs, artists, etc

I think it's possible that there are all sorts of reasons why these people could have vanished from public view. For example, maybe most of society's smartest people have all become socially-awkward corporate executives who already raced to the bottom and currently spend all of their brainpower outmaneuvering each other at office politics, or pumping out dozens of unique galaxy-brained resumes per day. Or maybe most of them have become software engineers who are smart enough to make $200k/y working from home one hour a day while appearing to work eight hours, and spend the rest of their time and energy hooked on major social media platforms (I've encountered several people in the Bay Area who do this).

It's difficult to theorize about invisible geniuses (or the absence of invisible geniuses) because it's unfalsifiable [? · GW]. But it's definitely possible that they could either secretly be in a glamorous place, like an underground network steering and coordinating multiple intelligence agencies (in which case all potential opposition might be doomed by default), or an unglamorous place, like socially awkward corporate executives struggling at office politics (office politics aren't a good fit for them due to social awkwardness), but they keep at it because they're still too smart to fail at the office politics and were never given a fair chance to find out about superintelligence [LW · GW] or human intelligence amplification [LW · GW].

Yeah it happens largely in the first few chapters, its not really a spoiler. Its the event the book was famous for.

I think that's an important insight (though I'm not sure how universal it is).  The Dark Forest effect may be happening at multiple levels.  Not only can't you find the people you expect in the forest, you can't even find the reasons might be hidden or work on better search or attraction methods to find them.  Or even hypothesize well enough to find evidence for hiding vs nonexistence.

It seems like a scale with "obviously bad" on one end, "annoying but not too bad" somewhere in the middle, and "okay but slightly worse than current group average" on the other end.

Sadly, even the last one has a potential to destroy your group in long term, if you keep adding people who are slightly below the average... thus lowering the average, and unknowingly lowering the bar for the next person slightly below the new average... and your group has less and less of the thing that the original members joined or created it for.

Kicking out the obviously bad person at least feels righteous. Kicking out the annoying one can make you feel bad. Kicking out the slightly-below-average person definitely makes you feel like an asshole.

(It is even more complicated in situations where the group members improve at something by practicing. In that case, the newbie is very likely currently worse than the group average, but you have to estimate their potential for improvement.)

Sometimes it can even make sense to reject new people who are actually less problematic than the worst current member, but still more problematic than the average. Just because your group can handle one annoying member, doesn't mean it will be able to handle two. (Also, who knows what kind of interaction may happen between the two annoying members.)

Yeah, I think this is an important explanation for why (in my preferred image), we’d find the faeries hiding under the leaves in the faerie forest.

To avoid behavior that’s costly to police, or shortcomings that are hard to identify, and also to attract virtues that are hard to define, we rely in part on private, reputation- and relationship-based networks.

These types of ambiguous bad behaviors are what I had in mind when I wrote “predatory,” but of course they are not necessarily so easy to define as such. They might just be uncomfortable, or sort of “icky sticky,” or even just tedious, and not only in a sexual way. The grandstanding blowhard or tireless complainer or self-righteous moralizer also fit the bill. Maybe the word “scrubs” is a better word?

That makes some sense to me. The most salient feature of the Dark Forest scenario, to me, is the one in which we're in a bad prisoner's game dilemma with something like the following payoff matrix:

• Cooperate/cooperate gets some finite positive utility for both players
• Defect/cooperate means ruin for the cooperator with equal or greater utility for the defector
• Defect/defect ruins one player with 50% probability

Of course, real-world decisions to participate in private events don't resemble this payoff matrix, which is why, for me, the Dark Forest scenario feels somehow too dramatic, or like it's too paranoid an account of the feeling of anxiety or boredom that comes with trying to connect with people in a new social setting full of strangers.

Or maybe I'd take that further and say that newcomers at parties often seem to operate as if they were in a Dark Forest scenario ("careful not to embarrass yourself, people will laugh at you if you say something dumb, probably everybody's mean here, or else annoying and foolish which is why they're at this public gathering, your feelings of anxiety and alienation are warranted!").  And it's much better if you realize that's not in fact the case. People there are like you - wanting to connect, pretty interesting, kind of anxious, just waiting for someone else to make the first move. There are all kinds of perfectly normal reasons people are choosing to hang out at a public gathering place rather than with their close friends, and if public gatherings seem "terrible," it's usually because of the instrinsic awkwardness of strangers trying to break the ice. They'd almost all be interesting and fun if they got to know each other and felt more comfortable.

But I do see the connection with the desire to avoid unpleasant strangers and the need to infer the existence of all these private get-togethers and communities.

To be clear I think it's generally actually fine to ask out loud "hey why isn't this happening?" (rather than quietly/privately). At least, this seems fine for all the examples in the OP.

The thing I'm cautioning against is forming the strong belief "this isn't happening, people must be crazy/blind to what needs-to-be-done" and then boldly charging ahead.