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Yvain comments on Rationality quotes: April 2010 - Less Wrong
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-- R Scott Bakker, Neuropath
You mean, like every Bayesian believes their prior is correct?
Prior can't be judged. It's not assumed to be "correct". It's just the way you happen to process new info and make decisions, and there is no procedure to change the way it is from inside the system.
Locked in, huh? Then I don't want to be a Bayesian.
If someone was locked in to a belief, then they'd use a point mass prior. All other priors express some uncertainty.
Since you are already locked in in some preference anyway, you should figure out how to compute within it best (build a FAI).
What makes you say that? It's not true. My preferences have changed many times.
Distinguish formal preference and likes. Formal preference is like prior: both current beliefs and procedure for updating the beliefs; beliefs change, but not the procedure. Likes are like beliefs: they change all the time, according to formal preference, in response to observations and reflection. Of course, we might consider jumping to a meta level, where the procedure for updating beliefs is itself subject to revision; this doesn't really change the game, you've just named some of the beliefs changing according to fixed prior "object-level priors", and named the process of revising those beliefs according to the fixed prior "process of changing object-level prior".
When formal preference changes, it by definition means that it changed not according to (former) formal preference, that is something undesirable happened. Humans are not able to hold their preference fixed, which means that their preferences do change, what I call "value drift".
You are locked in in some preference in normative sense, not factual. This means that value drift does change your preference, but it is actually desirable (for you) for your formal preference to never change.
I object to your talking about "formal preference" without having a formal definition. Until you invent one, please let's talk about what normal humans mean by "preference" instead.
I'm trying to find a formal understanding of a certain concept, and this concept is not what is normally called "preference", as in "likes". To distinguish from the word "preference", I used the label "formal preference" in the above comment to refer to this concept I don't fully understand. Maybe the adjective "formal" is inappropriate for something I can't formally define, but it's not an option to talk about a different concept, as I'm not interested in a different concept. Hence I'm confused about what you are really suggesting by
For the purposes of FAI, what I'm discussing as "formal preference", which is the same as "morality", is clearly more important than likes.
I'd be willing to bet money that any formalization of "preference" that you invent, short of encoding the whole world into it, will still describe a property that some humans do modify within themselves. So we aren't locked in, but your AIs will be.
What makes you say that Bayesians are locked in? It's not true. If they're presented with evidence for or against their beliefs, they'll change them.
You're talking about posteriors. They're talking about priors, presumably foundational priors that for some reason aren't posteriors for any computations. An important question is whether such priors exist.
But your beliefs are your posteriors, not your priors. If the only thing that's locked in is your priors, that's not a locking-in at all.
That's not obvious. You'd need to study many specific cases, and see if starting from different priors reliably predicts the final posteriors. There might be no way to "get there from here" for some priors.
When we speak of the values that an organism has, which are analogous to the priors an organism starts with, it's routine to speak of the role of the initial values as locking in a value system. Why do we treat these cases differently?
I have heard some argue for adjusting priors as a way of dealing with deductive discoveries since we aren't logically omniscient. I think I like that solution. Realizing you forgot to carry a digit in a previous update isn't exactly new information about the belief. Obviously a perfect Bayesian wouldn't have this issue but I think we can feel free to evaluate priors given that we are so far away from that ideal.
But one man's prior is another man's posterior: I can use the belief that a medical test is 90% specific when using it to determine whether a patient has a disease, but I arrived at my beliefs about that medical test through Bayesian processes - either logical reasoning about the science behind the test, or more likely trying the test on a bunch of people and using statistics to estimate a specificity.
So it may be mathematically wrong to tell me my 90% prior is false, but the 90% prior from the first question is the same 90% posterior from the second question, and it's totally kosher to say that the 90% posterior from the second question is wrong (and by extension, I'm using the "wrong prior")
The whole reflective consistency thing is that you shouldn't have "foundational priors" in the sense that they're not the posterior of anything. Every foundational prior gets checked by how well it accords with other things, and in that sense is sort of a posterior.
So I agree with cousin_it that it would be a problem if every Bayesian believed their prior to be correct (as in - they got the correct posterior yesterday to use as their prior today).
Vladimir is using "prior" to mean a map from streams of observations to probability distributions over streams of future observation, not the prior probability before updating. Follow the link in his comment.
Bayesians don't believe they lucked into their priors. They have a reflectively consistent causal explanation for their priors.
Even if their explanation were correct, they would still have lucked into them. Others have different priors and no doubt different causes for their priors. So those Bayesians would have been lucky, in order to have the causes that would produce correct priors instead of incorrect ones.
But that still doesn't need to be luck. I got my priors offa evolution and they are capable of noticing when something works or doesn't work a hundred times in a row. True, if I had a different prior, I wouldn't care about that either. But even so, that I have this prior is not a question of luck.
It is luck in a sense - every way that your opinion differs from someone else, you believe that factors outside of your control (your intelligence, your education, et cetera) have blessed you in such a way that your mind has done better than that poor person's.
It's just that it's not a problem. Lottery winners got richer than everyone else by luck, but that doesn't mean they're deluded in believing that they're rich. But someone who had only weak evidence ze won the lottery should be very skeptical. The real point of this quote is that being much less wrong than average is an improbable state, and you need correspondingly strong evidence to support the possibility. I think many of the people on this site probably do have some of that evidence (things like higher than average IQ scores would be decent signs of higher than normal probability of being right) but it's still something worth worrying about.
I think I agree with that: There's nothing necessarily delusive about believing you got lucky, but it should generally require (at least) an amount of evidence proportional to the amount of purported luck.
Then it would make sense to use some evolutionary thingy instead of Bayesianism as your basic theory of "correct behavior", as Shalizi has half-jokingly suggested.
Priors can't be correct or incorrect.
(Clarified in detail in this comment.)
Sounds mysterious to me. Priors are not claims about the world?
Not quite. They are the way you process claims about the world. A claim has to come in context of a method for its evaluation, but prior can only be evaluated by comparing it to itself...
This downvoting should be accompanied with discussion. I've answered the objections that were voiced, but naturally I can't refute an incredulous stare.
The normal way of understanding priors is that they are or can be expressed as joint probability distributions, which can be more or less well-calibrated. You're skipping over a lot of inferential steps.
Right. We could talk of quality of an approximation to a fixed object that is defined as the topic of a pursuit, even if we can't choose the fixed object in the process and thus there is no sense in having preferences about its properties.
I can't tell what you're talking about.
Say, you are trying to figure out what the mass on an electron is. As you develop your experimental techniques, there will be better or worse approximate answers along the way. It makes sense to characterize the approximations to the mass you seek to measure as more or less accurate, and characterize someone else's wild guesses about this value as correct or not correct at all.
On the other hand, it doesn't make sense so similarly characterize the actual mass of an electron. The actual mass of an electron can't be correct or incorrect, can't be more or less well-calibrated -- talking this way would indicate a conceptual confusion.
When I talked about prior or preference in the above comments, I meant the actual facts, not particular approximations to those facts, the concepts that we might want to approximate, not approximations. Characterizing these facts as correct or incorrect doesn't make sense for similar reasons.
Furthermore, since they are fixed elements of ideal decision-making algorithm, it doesn't make sense to ascribe preference to them (more or less useful, more or less preferable). This is a bit more subtle than with the example of the mass of an electron, since in that case we had a factual estimation process, and with decision-making we also have a moral estimation process. With factual estimation, the fact that we are approximating isn't itself an approximation, and so can't be more or less accurate. With moral estimation, we are approximating the true value of a decision (event), and the actual value of a decision (event) can't be too high or too low.
They can be more or less useful, though.
According to what criterion? You'd end up comparing a prior to the prior you hold, with the "best" prior for you just being the same as yours. Like with preference. Clearly not the concept Unknowns was assuming -- you don't need luck to satisfy a tautology.
Of being better at predicting what happens, of course.
You can't judge based on info you don't have. Based on what you do have, you can do no better than current prior.
But you can go and get info, and then judge, and say, "That prior that I held was wrong."
You're speaking as if all truth were relative. I don't know if you mean this, but your comments in this thread imply that there is no such thing as truth.
You've recently had other discussions about values and ethics, and the argument you're making here parallels your position in that argument. You may be trying to keep your believes about values, and about truths in general, in syntactic conformance. But rationally I hope you agree they're different.
I am in violent agreement.