I go to a lot of rationalist meetups. I quite enjoy them, and it’s often because of the people who go to the meetups. There’s a number of assumptions you might have about people who go to rationalist meetups, and many of them are mostly true. However, there is a difference between most examples and all examples. Most birds can fly. 

In the tradition of Falsehoods Programmers Believe About Names then, I would like to present to you the following Falsehoods You Might Believe About People At A Rationalist Meetup. These are drawn from things calling themselves an Astral Codex Ten/Slate Star Codex meetup, a LessWrong meetup, or a Rationalist meetup. I am bucketing ACX, LessWrong, and Rationalist groups together. I'm not counting Prediction Market meetups or Effective Altruism meetups or TPOT meetups or house parties that happen to be full of rationalists or any of the other variety of 'adjacent' communities. We're going purely by what the meetup announcement or group called itself.

All of these have at least one counterexample I have personally encountered. 

• Attendees will introduce themselves with something that sounds like a normal name.
• Attendees will introduce themselves with the username they use online.
• Attendees will introduce themselves with the same name from meetup to meetup.
• Attendees are old enough to enter a pub.
• Attendees are old enough to drive.
• Attendees are old enough to be toilet trained. (Put another way: no attendees are bringing small children.)
• Attendees went to college
• Attendees have a simple answer to "so what do you do for work?"
• Attendees have an answer to "so what do you do for work?" that isn't a variation on "I don't."
• Attendees are able-bodied enough to walk up two flights of stairs without issue.
• Attendees are financially comfortable enough that eating out at a restaurant once or twice a month is not a barrier.
• Attendees are not so financially well off that they wouldn't be able to buy the restaurant outright if they wanted to.
• Attendees can see, at least well enough to read a street sign.
• Attendees are vegan.
• Or vegetarian.
• Or at least will eat a protein which is not meat. This includes, say, Impossible Burgers.
• Contrariwise, attendees will eat meat.
• This hypo-allergenic cereal is fine though, right? Or at least fine enough that nobody's going to be sick if they eat it?
• Attendees consider themselves part of the Effective Altruism community.
• Attendees consider themselves part of at least one of the ACX or LessWrong community.
• Attendees consider themselves in anyway way a rationalist.
• Attendees have ever been to a previous meetup, or expect to go to a future meetup.
• Attendees know at least one other person present.
• Attendees use Facebook.
• Or Discord.
• Or WhatsApp.
• Or Twitter X.
• Or will reliably see an email you send them.
• Attendees have a LessWrong account.
• Attendees regularly read at least one of LessWrong or Astral Codex Ten.
• Attendees have read at least one essay on LessWrong or Astral Codex Ten. Yes, that includes having read at least one post of The Sequences.
• Alright but surely attendees know what at least one of LessWrong or Astral Codex Ten are. ("A web forum" or "a blog" would be close enough.)
• Attendees read some other long-form writing that you’d recognize as obviously rationalist.
• Attendees are atheists.
• Attendees are, if not atheists, then agnostic or the kind of religious where it’s low-key and not a big part of their life.
• Attendees obviously didn't vote for [insert name here] last election.
• Attendees obviously didn't run notable parts of the campaign for [insert name here] last election.
• Attendees have gotten at least one Covid-19 vaccine.
• Attendees speak fluent English.
• Attendees read English, at least well enough to read that short essay picked as the discussion topic.
• You're kidding about that last one, right?
• Attendees will be dressed normally. You know, in a suit and jacket.
• Er, I mean dressed normally, like in a ragged t-shirt with inscrutable memes on it.
• Sorry, I meant dressed normally, which at least means they aren't in pajamas.
• What's a yukata?
• Okay, but the person wearing the yukata was in Japan or somewhere else you'd culturally expect a yukata, right?
• Attendees are good at all the skills you might expect of a rationalist.
• Attendees are skilled at any given rationality technique or skill.
• Attendees basically agree what skills those would be or that they'd be good to have.
• Attendees are comfortable with alcohol at the meetup.
• Attendees are neither drunk nor high at the meetup.
• Attendees are comfortable with it being known (say, via pictures on Facebook) that they attended a rationalist meetup.
• Attendees have not been banned from another rationalist group.
• The organizer regularly reads at least one of LessWrong or Astral Codex Ten.
• The organizer is good at any given rationality technique or skill. Any of them at all.
• The organizer considers themself a rationalist.
• The organizer has not been banned from another rationalist group.

Many of these are mostly true, and I’m not recommending you heroically try to accommodate every exception to this list. 

The initial seed of this list was a conversation I was having at a meetup during late 2021 where the person I was talking to said, quote not verbatim but very close, "obviously everyone at a rationalist meetup has gotten the Covid-19 vaccine" only to have the person behind them immediately say "I haven't."

The thing that convinced me to post this list was a conversation with someone who said, quote not verbatim but very close, “If there was any conflict, we’re rationalists, we could settle it rationally.” As far as I am aware, none of the people involved in that ‘we’ had ever had any formal rationality training, at least one of them later said that they didn’t consider themselves a rationalist, and [spoilers] there was conflict that I do not consider to have been settled rationally. 

The primary intended use case of this list is to give a kind of heads up and mitigate the surprising clash of expectations that otherwise might happen. 

The secondary use case is this: Consider which of these bullet points you might want to be true or untrue about your local rationality group, and what actions you might need to take in order to make that happen.