Not the question Keltham was expecting, but Okay Fine.
"I'd guess the smartest, the most careful - we have a specialized term for that as a usually-mostly-stable quality of a person, maybe 'conscientiousness' would be the best translation here? I expect they'd look for things you can test in childhood that somebody has shown to correlate with keeping oaths in adulthood later and being very unlikely to go unstable under stress. I mean, the real answer to your question is that we have prediction markets, people betting on outcomes, with which a lot of people betting, operates as a kind of summary of everyone's best guess at the probabilities of definite observations being made later. And, I would strongly expect, the Keepers have secret prediction markets that only Keeper institutions can bet on, because it's a secret what exactly they're betting on, because they don't want parents pushing their kids into faking their way into joining the Keepers. But I imagine the secret prediction market topics say, is this person going to end up passing the following competence tests, will they end up measurably mastering the Way that Keepers keep, will it be recorded that any spilled secrets get traced back to them, will they ever be observed to have broken an oath they took. Are they going to get along with other Keepers the right amount, neither too conforming nor too iconoclastic. Will they end up being promoted, are they going to report enjoying their work and be happy at it in observable ways... now that I say it out loud, I feel like there's probably more in the secret markets than that. That's the kind of market you run to find out if a kid is going to be a good matchmaker or doctor, not to find out who ought to be a Keeper. The thing is, prediction markets are ultimately betting markets and they have to resolve in definite observations at some point. So there's some sort of observable thing that would happen to you over the course of your career as a Keeper that a bet would have to be about, in order for it to ever pay out. In terms of your local system - I don't quite know if they'd qualify as 'Good', they do get paid for what they do, in both money and reputation, but they definitely lean further Good than average - they are, in the end, spending their lives taking care of other people."
"I've always felt weird about the aspect where Keepers are significantly more Good than I am, to be frank. Even if you nod respectfully at them and pay a tiny fraction of their salaries, they're still doing you this huge favor, that you didn't ask for - some of which probably has to be done in order to make society livable for you at all - but they're doing more of it than I'd ask for, if it was up to me - supposedly on my behalf. And they aren't doing it wrong, that I know about, or hurting me in any way, that I know about. But they're still doing more of what they do, than I'd have really asked for... though I'm not a typical dath ilani, the typical dath ilani probably feels more on median-average like there's the right amount of Keepering going on. Though actually, by the nature of their jobs, there's got to be more of it going on than we really know a specific reason for? So some reasons for the Keepers' existences are hidden, and maybe my own first-impression feelings are closer to average and I'm just failing to adjust for predictable updates on the hidden info if I could see it... the whole Keeper thing is probably one of the objectively weirder institutions in dath ilan from an outside viewpoint, along with the Surreptitious Head Removers, the Official Government Con Artists, and the Planetary Emergency Rehearsal Festivals. All of which have completely logical and reasonable reasons behind them, and are still understood and acknowledged even by Civilization generally to be some of the weirder things they have talked themselves into doing."
"Though, I mean, I don't disagree with the reasons, I can see why something like the Keepers need to exist. Very stable geniuses can extensively develop thoughts that will wreck less stable people's minds, often without them even meaning to do that. Even pursuing Lawfulness too far can sometimes end up that way. Human beings are not designed to work great when we push ourselves harder and harder in the direction of Lawfulness - I mean, we're not designed at all, but I doubt it's something our distant ancestors bred themselves to be able to do safely. I imagine that Keepers are people who by nature are smart and resilient and exceptionally stable in the face of internal insult, able to tolerate weird stuff going on inside or outside their own heads, and what they spend that internal resilience on is going way further in the direction of Law than their ancestors a million years earlier were pseudo-designed to do."
"And, I mean, I'm sure the Keepers have got a pretty good idea about who can do that by age ten. But that's not because I could take one glance at a ten-year-old and figure out who'd be a good Keeper. It's because, I confidently predict, the Keepers observe a lot of facts about ten-year-olds, and they keep excellent records of long-term outcomes, and they train people with very high measured intelligence to make good predictions about it. Come to think, I wouldn't be surprised if the Keepers had a secret prediction market about me somewhere in their systems, saying exactly what my chances were of succeeding at my life goals, and people like me aren't told those predictions because that's exactly the kind of information that - can be a bit - more Lawfulness than we're really happy having in our lives. And if you can predict that actually a kid is going to be totally okay with knowing that information, then maybe you try to make them a Keeper. Or maybe what they predict isn't so much kids starting out imperturbable, as that you'll end up driven to face down whatever kind of internal bumps you face, in order to be able to face any kind of disturbing truth and not allow your potential to be limited by the disorder of your own mind... I don't know. I didn't want to be a Keeper. They weren't the kind of weird I wanted to be."