Who is "they" exactly, and how can they estimate the probability of a future event based on zero priors and a total lack of scientific evidence?

> Who is "they" exactly

Rationalists, mostly self-identified.

> how can they estimate the probability of a future event based on zero priors and a total lack of scientific evidence?

As best as they can, because at the end of the day you still need to make decisions (You can of course choose to do nothing and ignore the risk, but that's not a safe, neutral option). Which means either you treat it as if it had a particular probability, or you waste money and effort doing things in a less effective way. It's like preparing for global warming or floods or hurricanes or what have you - yes, the error bars are wide, but at the end of the day you take the best estimate you can and get on with it, because anything else is worse.

But their best estimate is utterly worthless with zero basis in actual reality.

Well when you hear a possible disaster is coming, what do you do? Implicitly you make some kind of estimate of the likelihood - ultimately you have to decide what you're going to do about it. Even if you refuse to put a number on it or talk about it publicly, you still made an estimate that you're living by. Talking about it at least gives you a chance to compare and sanity-check.

Well I have some common sense so I don't react to things that I "hear" from random worthless morons.

> I don't react to things that I "hear" from random worthless morons.

Which is to say that you've made an estimate that the probability is, IDK, <5%, <1%, or some such.

Adding numbers to your reasoning, when there is no obvious source for these probabilities (we aren’t calculating sports odds or doing climate science), is not really any different than writing a piece of fiction to make your point. It’s the same basic thing that objectivists did, and why I dismiss most “Bayesian reasoning” arguments out of hand.

Which content did you engage with that led you to the conclusion that they base their estimates with “no obvious source for these probabilities”? A link would be appreciated