"Well, in a fundamental sense, advertisements aim to overcome obstacles posed by different incentives to achieving common knowledge about product qualities!  That is, if I was good enough friends with somebody, such that I thought they knew me very well and had my interests at heart, they could just tell me they were very sure I ought to buy something, and I'd buy it!  In principle, the problem of advertising is posed when somebody who knows me less well still has justified belief that I, or a bunch of people in a class similar to me, ought to make a trade we haven't already made.  The basic difficulty of this problem class is that you can also imagine people who don't have such valid knowledge, but are incentivized to deceive themselves about how good their product is, because they capture a portion of the gains from trade.  And the basic danger of advertising is that if you have a group of people like that, they may be incentivized to burn all of their gains from trade on advertising - getting people to trade with them rather than somebody else.  Like, you and I are both producing flavored drinks, which are actually exactly as good as each other, and we each capture 10 dollars... that is not how large our monetary unit of account is, English, but fine, 10 dollars.  We each profit 10 dollars each time we sell a drink.  If I'm self-deceptive about my drink being superior, and I pay $5 to produce an advertisement promising that and thereby convince one consumer to switch from your drinks to mine, I gain net $5 but you lose $10 and the consumer is no better off and also pays switching costs or costs of cognition, so social surplus has been destroyed.  There's a mild tax on marketing, more symbolic than anything else at current levels, but it does remind people of how easily it can go negative-sum given the incentives and less than perfect information.  So the basic challenge in advertising is to convince the customer that you actually do know about a product that's better for them to buy - overcoming my skepticism about my conflict of interest with whoever wants me to trade with them."

"So, in practice, an ad might look like a picture of the product, with a brief description of what the product does better that tries to sound very factual and quantitative so it doesn't set off suspicions.  Plus a much more glowing quote from a Very Serious Person who's high enough up to have a famous reputation for impartiality, where the Very Serious Person either got paid a small amount for their time to try that product, or donated some time that a nonprofit auctioned for much larger amounts; and the Very Serious Person ended up actually impressed with the product, and willing to stake some of their reputation on recommending it in the name of the social surplus they expect to be thereby produced.  Plus a Network trail to a much longer report from an old, even higher-reputation institution testing whatever the product's merits were.  And the upshot is that people can find out about things they didn't know they wanted to trade, but could validly benefit from trading, with their cost of information partially paid by somebody who also expects to benefit from the trade and already knows about it; without all of Civilization's gains from trade being dissipated in a negative-sum fight about who trades with who, driven by an arms race in deceptive advertisements.  To me, at least, this doesn't sound like a weird private quirk of our Civilization.  It sounds coherent with some of the most fundamental and important theorems about systems of multiple agents, which states that in principle they end up on a multiagent-optimal frontier, and in practice they end up very close to a multiagent-optimal frontier."

"So, uh, it's not actually necessary for Coke advertisers to believe Coke is objectively superior to Pepsi in order for them to produce Coke advertisements, for one. Companies do pay people to try and review products sometimes but there is not a special category 'very serious person' that everyone listens to because we're not a monoculture. Also flavored drinks and lots of other products are matter of personal taste as much as or more than objective quality. Also very boring advertisements listing statements about objective quality... don't... move as much product... so they have been moved away from in recent decades."

"And that is an incredibly bizarre anomaly just like your lunar eclipses, except more disturbing because in this case I understand the theorems about agent behavior that they're violating, and I would have thought those theorems would generalize across widely different laws of physics.  Something is messing with your minds."

"I would ask how your metaculture is meant to have, in practice, arisen from a state of nature, except you have acknowledged to me you don't know because it's being deliberately hidden from you."

"And I don't know what the Past Infohazard was, but if it also existed here and this is somehow what happens if you don't try to causally screen it off from your civilization, I am feeling a whole lot more on board than I used to be with the extraordinarily extreme measures our Civilization took to suppress it.  No offense or anything."

"It's okay if you don't like it here. I wouldn't like it where you're from either."

"That is an extremely, profoundly credible statement which everybody on my world would believe immediately based on priors, and our reaction would be to fly out ten thousand venture capitalists to interrogate you about all the nice things you had, and all the ways in which our world was falling short, and which new businesses would be required to provide those things to you and lots of other people!  That your world does not react like this seems to indicate some much deeper and more profound and alarming asymmetry!"

"Unfortunately I care a lot about freedom of the press so your venture capitalists would have a very hard time convincing me I'd like it there."

"We'd - no.  I was going to say, we'd obviously build an experimental region that was based on your whole world as much as possible, to observe what went on when all your preferred changes were tried simultaneously, in case there was a great synergy that local experiments would never hill-climb for us.  But if you can run non-magical experiments on genetics that cause mass civilian casualties that made your civilization completely give up on awareness of or influence over its own population genetics... maybe we really wouldn't try it your way, even in a small region.  What happened, exactly?  I'm starting to feel genuinely concerned about whether anything I might do is liable to blow up something I didn't understand and kill a hundred thousand people."

"Somebody thought some particular groups of other people were genetically inferior and decided to round up and murder as many of them as possible and some other people objected and there was a war. Is the extreme oversimplification of World War II. You are - I'd say you aren't going to do it by accident but I actually think it's really likely that what your history screening is covering up is lots of genocide much like that one of whoever wouldn't go along with your metaculture so maybe you are at some risk of doing it yourself."

"That contradicts theorems about how dignified people do things and therefore we would not do that and your world is VERY VERY DISTURBING and you should be more interested in fixing it and something is probably messing with your mind to make you less interested in fixing it."

"You don't think your secret censored history contains a genocide because it wouldn't be dignified?"

"Three-year-olds don't end up that far off from a multiagent-optimal frontier!  I know this because I was three years old and I never genocided anybody at all!"

"Congratulations, Earth three year old don't genocide people either!"

"Good!  We're making progress.  What is the earliest point at which your people start committing genocides?  One of the educational processes between age three and that is going wrong."

"Thellim, we aren't a monoculture, there is not a specific set of educational processes to intervene on."

"Perhaps, from my perspective, all of your educational processes are broken in very similar ways, but we can start by asking which educational process produces the greatest number of genociders per capita."

"That would be the Nazis and the Soviet Union at three apiece on Wikipedia's list followed by the Ottoman Empire at two but the takeaway lessons there are mostly that fascism and communism are bad... I'm not actually sure what was up with the Ottomans, I haven't read much about them."

"Isabella, you keep saying 'monoculture' but so far as I can tell your alternative is that some of your subcultures raise kids to commit genocides and some don't.  I'm not sure this is a good place to maintain persistent variance inside a civilization."

"I keep saying 'monoculture' because you keep talking like it is possible on your planet for someone to go 'oh, this doesn't look like a good place to maintain persistent variance inside a civilization' and then they alter the entire civilization to patch that and here there is no one who can do that."

"Nobody can produce public goods and there are no coordinative global institutions, yes, I noticed.  The reason why this worries me is not that I think this is a thing normal humans do without magic, it's a thing I can prove that general agents with intelligence do without magic."

Isabella snorts.

They board the subway. Isabella gestures at her cane and gets someone to yield their seat for her.

"All of these people are going to roughly the same place we are, to the point we need a long train of containers just for everybody making this trip...?  This isn't an anomaly the same way as eclipses, but I suspect something in the back of my mind is guessing some number wrong by four orders of magnitude, or has some other mistaken assumption."

"Uh, New York City has about eight million people in it, many people do not have cars for reasons aforementioned so the subway's popular."