# Learning Normativity: A Research Agenda

*(Related to* [*Inaccessible Information*](https://www.alignmentforum.org/posts/ZyWyAJbedvEgRT2uF/inaccessible-information)*,* [*Learning the Prior*](https://www.alignmentforum.org/posts/SL9mKhgdmDKXmxwE4/learning-the-prior)*, and* [*Better Priors as a Safety Problem*](https://www.alignmentforum.org/posts/roA83jDvq7F2epnHK/better-priors-as-a-safety-problem)*. Builds on several of my* [*alternate alignment ideas*](https://www.lesswrong.com/s/SBfqYgHf2zvxyKDtB)*.)*

I want to talk about something which I'll call *learning normativity*. What is normativity? Normativity is correct behavior. I mean something related to the fuzzy concept humans convey with the word "should". I think it has several interesting features:

*   Norms are the result of a complex negotiation between humans, so they shouldn't necessarily be thought of as the result of maximizing some set of values. This distinguishes learning normativity from value learning.
*   A lot of information about norms is present in the empirical distribution of what people actually do, but you can't learn norms just by learning human behavior. This distinguishes it from imitation learning.
*   It's often possible to provide a lot of information in the form of "good/bad" feedback. This feedback should be interpreted more like [approval-directed learning](https://www.alignmentforum.org/posts/7Hr8t6xwuuxBTqADK/approval-directed-agents-1) rather than RL. However, approval should not be treated as a gold standard.
*   Similarly, it's often possible to provide a lot of information in the form of rules, but rules are not necessarily 100% true; they are just very likely to apply in typical cases.
*   In general, it's possible to get very rich *types* of feedback, but very *sparse*: humans get all sorts of feedback, including not only instruction on how to act, but also *how to think.*
*   Any one piece of feedback is suspect. Teachers can make mistakes, instructions can be wrong, demonstrations can be imperfect, dictionaries can contain spelling errors, reward signals can be corrupt, and so on.

Example: Language Learning
==========================

 A major motivating example for me is how language learning works in humans. There is clearly, to some degree, a "right way" and a "wrong way" to use a language. I'll call this *correct usage*.

One notable feature of language learning is that we don't always speak, or write, in correct usage. This means that a child learning language has to distinguish between mistakes (such as typos) and correct usage. (Humans do sometimes learn to imitate mistakes, but *we have a notion of not doing so*. This is unlike [GPT](https://www.lesswrong.com/tag/gpt) systems learning to imitate the empirical distribution of human text.)

This means we're largely doing something like unsupervised learning, but with a notion of "correct"/"incorrect" data. We're doing something like throwing data out when it's likely to be incorrect.

A related point is that we are better at *recognizing* correct usage than we are at *generating* it. If we say something wrong, we're likely able to correct it. In some sense, this means there's a foothold for intelligence amplification: we know how to generate our own training gradent.

Another fascinating feature of language is that although native speakers are pretty good at both recognizing and generating correct usage, *we don't know the rules explicitly*. The whole field of linguistics is largely about trying to uncover the rules of grammar.

So it's impossible for us to teach proper English by teaching the rules. Yet, we do know *some* of the rules. Or, more accurately, we know a set of rules that *usually* apply. And those rules are *somewhat* useful for teaching English. (Although children have usually reached fluency before the point where they're taught explicit English grammar.)

All of these things point toward what I mean by *learning normativity:*

*   We can tell a lot about what's normative by simply observing what's common, but the two are not exactly the same thing.
*   A (qualified) human can usually label an example as correct or incorrect, but this is not perfect either.
*   We can articulate a lot about correct vs incorrect in the form of rules; but the rules which we can articulate never seem to cover 100% of the cases. A linguist is a lot like a philosopher: taking a concept which is understood at an intuitive level (which a great many people can fluently apply in the correct manner), but struggling for years to arrive at a correct technical definition which fits the intuitive usage.

In other words, the overriding feature of normativity which I'm trying to point at is that nothing is ever 100%. Correct grammar is not defined by any (known) rules or set of text, nor is it (quite) just whatever humans judge it is. All of those things give a lot of information about it, but it could differ from each of them. Yet, on top of all that, basically everyone learns it successfully. This is very close to Paul's [Inaccessible Information](https://www.alignmentforum.org/posts/ZyWyAJbedvEgRT2uF/inaccessible-information): information for which we cannot concoct a gold-standard training signal, but which intelligent systems may learn anyway.

Another important feature of this type of learning: *there is a fairly clear notion of superhuman performance.* Even though human imitation is *most* of the challenge, we could declare something superhuman based on our human understanding of the task. For example, GPT is trained exclusively to imitate, so it should never exceed human performance. Yet, we could tell if a GPT-like system *did* exceed human performance:

*   Its spelling and grammar would be immaculate, rather than including humanlike errors;
*   its output would be more creative and exciting to read than that of human authors;
*   when good reasoning was called for in a text, its arguments would be clear, correct, and compelling;
*   when truth was called for, rather than fiction, its general knowledge would be broader and more accurate than a human's.

It seems very possible to learn to be better than your teachers in these ways, because humans sometimes manage to do it.

Learning in the Absence of a Gold Standard
==========================================

In statistics and machine learning, a "gold standard" is a proxy which we treat as good enough to serve as ground truth for our limited purposes. The accuracy of any other estimate will be judged by comparison to the gold standard. This is similar to the concept of "operationalization" in science.

It's worth pointing out that in pure Bayesian terms, there is nothing especially concerning about learning in the absence of a gold standard. I have data X. I want to know about Y. I update on X, getting P(Y|X). No problem!

However, that only works if we have the right prior. We could try to [learn the prior from humans](https://www.lesswrong.com/posts/SL9mKhgdmDKXmxwE4/learning-the-prior), which gets us 99% of the way there... but as I've mentioned earlier, human imitation does not get us all the way. Humans don't perfectly endorse their own reactions.

(Note that whether "99% of the way" is good enough for AI safety is a separate question. I'm trying to define the Big Hairy Audacious Goal of learning normativity.)

Actually, I want to split "no gold standard" into two separate problems.

1.  **There's no type of feedback which we can perfectly trust.** If humans label examples of good/bad behavior, a few of those labels are going to be wrong. If humans provide example inferences for learning the prior, some of those example inferences are (in a very real sense) wrong. And so on.
2.  **There's no level at which we can perfectly define the loss function.** This is a consequence of no-perfect-feedback, but it's worth pointing out separately.

No Perfect Feedback
-------------------

I think I've made the concept of no-perfect-feedback clear enough already. But what could it mean to *learn* under this condition, in a machine-learning sense?

There are some ideas that get part of the way:

*   [Jeffrey updates](https://www.lesswrong.com/posts/xJyY5QkQvNJpZLJRo/radical-probabilism-1#Generalized_Updates) let us update to a *specific probability* of a given piece of feedback being true, rather than updating to 100%. This allows us to, EG, label an image as 90%-probable cat, 9%-probable dog, 1% broad distribution over other things.
    *   This allows us to give some evidence, while allowing the learner to decide later that what we said was wrong (due to the accumulation of contrary evidence).
    *   This seems helpful, but we need to be *confident that those probability assignments are themselves normatively correct*, and this seems like it's going to be a pretty big problem in practice.
*   [Virtual evidence](https://www.lesswrong.com/posts/xJyY5QkQvNJpZLJRo/radical-probabilism-1#Virtual_Evidence) is one step better: we don't have to indicate what actual probability to update to, but instead only indicate the *strength* of evidence.
    *   Like Jeffrey updates, this means we can provide strong evidence while still allowing the system to decide later that we were wrong, due to the accumulation of contradicting evidence.
    *   Unlike Jeffrey updates, we don't have to decide what probability we should update *to*, only the direction and strength of the evidence.
*   [Soft labels](https://ai.stackexchange.com/questions/9635/about-the-definition-of-soft-label-and-hard-label) in machine learning provide a similar functionality. In EM learning, a system learns from its own soft labels. In [LO-shot learning](https://arxiv.org/abs/2009.08449), a system leverages the fact that soft labels contain more information than hard labels, in order to learn classes with less than one examples per class.

However, although these ideas capture *weak feedback* in the sense of less-than-100%-confidence feedback, they don't capture the idea of ***reinterpretable feedback:***

*   A system should ideally be able to learn that *specific **types** of feedback are erroneous,* such as [corrupted-feedback cases in reinforcement learning](https://arxiv.org/abs/1705.08417). A system might learn that my feedback is lower quality right before lunch, for example.
*   A system should be able to *preserve the overall meaning of a label despite an ontology shift*. For example, deciding that fruit/vegetable is not a useful taxonomic or culinary distinction should not destroy the information gained from such labels. Or, if human feedback includes formal English grammar, that information should not be totally discarded if the system realizes that the rules don't fully hold and the supposed grammatical categories are not as solid as claimed.
*   Feedback should be associated with *a cloud of possible interpretations*. When humans say "weird", we often mean "unusual", but also sometimes mean "bad". When humans say we don't understand, we often *really* mean we don't *endorse.* A system should, ideally, be able to *learn a mapping* from the feedback humans actually give to what they really mean. This is, in any case, the general solution to the previous bullet points.

But "learning a mapping from what feedback is given to what is meant" appears to imply that there is *no fixed loss function* for machine learning to work on, which would be a serious challenge. This is the subject of my point #2 from earlier:

No Perfect Loss Function
------------------------

We can frame (some) approaches to the [value specification problem](https://www.lesswrong.com/posts/yXPT4nr4as7JvxLQa/classifying-specification-problems-as-variants-of-goodhart-s) in a sequence of increasingly sophisticated approaches (similar to the hierarchy I discussed in my "stable pointers to value" posts ([1](https://www.lesswrong.com/s/SBfqYgHf2zvxyKDtB/p/5bd75cc58225bf06703754b3),[2](https://www.lesswrong.com/s/SBfqYgHf2zvxyKDtB/p/wujPGixayiZSMYfm6),[3](https://www.lesswrong.com/s/SBfqYgHf2zvxyKDtB/p/bEa4FuLS4r7hExoty))):

1.  *Direct specification of the value function.* This fails because we don't know what values to specify, and expect anything we can write down to be highly Goodhart-able.
2.  *Learning human values.* We delegate the specification problem to the machine. But, this leaves us with the meta problem of specifying how to learn. Getting it wrong can lead to wireheading and human manipulation. Even in settings where this is impossible, we face Stuart's [no-free-lunch results](https://www.lesswrong.com/posts/LRYwpq8i9ym7Wuyoc/other-versions-of-no-free-lunch-in-value-learning).
3.  *Learning to learn human values.* Stuart suggests that we can get around the no-free-lunch results by [loading the right prior information into the learner](https://www.lesswrong.com/posts/CSEdLLEkap2pubjof/research-agenda-v0-9-synthesising-a-human-s-preferences-into), in keeping with his more general belief that [Bayesian reasoning is fine as long as it has the right prior information](https://www.lesswrong.com/posts/uL74oQv5PsnotGzt7/all-i-know-is-goodhart). But this seems to go back to the problem of learning the human prior. So we could apply a learning approach again here. But then we again have a specification problem for the loss function for *this* learning...
4.  ...

You get the picture. We can keep pushing back the specification problem by learning, learning to learn, learning to learn to learn... Each time we push the problem back, we seem to gain *something*, but we're also stuck with a *new* specification problem at the meta level.

Could we specify a way to learn at *all the levels,* pushing the problem back infinitely? This might sound absurd, but I think there are ways to accomplish this. We need to somehow "collapse all the levels into one learner" -- otherwise, with an infinite number of levels to learn, there would be no hope. There needs to be very significant generalization across levels. For example, Occam's razor is a good starting rule of thumb at all levels (at least, all levels above the lowest). However, [because Occam is not enough, it will need to be augmented with other information](https://www.lesswrong.com/posts/Xy2AYxpWqJWedFfcD/learning-values-in-practice).

[Recursive reward modeling](https://medium.com/@deepmindsafetyresearch/scalable-agent-alignment-via-reward-modeling-bf4ab06dfd84) is similar to the approach I'm sketching, in that it recursively breaks down the problem of specifying a loss function. However, it doesn't really take the same learning-to-learn approach, and it also doesn't aim for a monolithic learning system that is able to absorb information at all the levels.

I think of this as necessary learning-theoretic background work in order to achieve [Stuart Armstrong's agenda](https://www.lesswrong.com/posts/CSEdLLEkap2pubjof/research-agenda-v0-9-synthesising-a-human-s-preferences-into), although Stuart may disagree. The goal here is to provide one framework in which all the information Stuart hopes to give a system can be properly integrated.

Note that *this is only an approach to* [***outer** alignment*](https://www.lesswrong.com/tag/outer-alignment). The [inner alignment problem](https://www.lesswrong.com/tag/inner-alignment) is a separate, and perhaps even more pressing, issue. The next section could be of more help to inner alignment, but I'm not sure this is overall the right path to solve that problem.

Process-Level Feedback
======================

Sometimes we care about *how we get* the answers, not just what the answers are. That is to say, sometimes we can point out problems with methodology without being able to point to problems in the answers themselves. Answers can be suspect based on how they're computed.

Sometimes, points can only be effectively made in terms of this type of feedback. Wireheading and human manipulation can't be eliminated through object-level feedback, but we could point out examples of the wrong and right types of reasoning.

Process-level feedback blurs the distinction between inner alignment and outer alignment. A system which accepts process-level feedback is essentially exposing all its innards as "outer", so *if we can provide the appropriate feedback*, there should be no separate inner alignment problem. (Unfortunately, it must be admitted that it's quite difficult to provide the right feedback -- due to transparency issues, we can't expect to understand all models in order to give feedback on them.)

I also want to emphasize that we want to give feedback on the *entire* process. It's no good if we have "level 1" which is in charge of producing output, and learns from object-level feedback, but "level 2" is in charge of accepting process-level feedback about level 1, and adjusting level 1 accordingly. Then we still have a separate inner alignment problem for level 2.

This is the same kind of hierarchy problem we saw in "No Perfect Loss Function". Similarly, we want to collapse all the levels down. We want *one* level which is capable of accepting process-level feedback about *itself*.

Learning from Process-Level Feedback
------------------------------------

In a Bayesian treatment, process-level feedback means *direct feedback about hypotheses*. In theory, there's no barrier to this type of feedback. A hypothesis can be ruled out by fiat just as easily as it can be ruled out by contradicting data. 

However, this isn't a very powerful learning mechanism. If we imagine a human trying to inner-align a Bayesian system this way, the human has to *find and knock out every single malign hypothesis*. There's no generalization mechanism here.

Since detecting malign hypotheses is difficult, we want the learning system to help us out here. It should generalize from examples of malign hypotheses, and [attempt to draw a broad boundary](https://www.lesswrong.com/posts/PADPJ3xac5ogjEGwA/defeating-goodhart-and-the-closest-unblocked-strategy) around malignancy. Allowing the system to judge itself in this way can of course lead to malign reinterpretations of user feedback, but hopefully allows for a [basin of attraction](https://www.lesswrong.com/posts/fkLYhTQteAu5SinAc/corrigibility#2__Corrigible_agents_become_more_corrigible_aligned) in which benevolent generalizations can be learned.

For example, in Solomonoff induction, we have a powerful hierarchical prior in the distribution on program prefixes. A program prefix can represent any kind of distribution on hypotheses (since a program prefix can completely change the programming language to be used in the remainder of the program). So one would *hope* that knocking out hypotheses would reduce the probability of all other programs which share a prefix with that hypothesis, representing a generalization "this branch in my hierarchical prior on programs seems iffy". (As a stretch goal, we'd also like to update against other similar-looking branches; but we *at least* want to update against *this* one.)

However, no such update occurs. The branch loses mass, due to losing one member, but programs which share a prefix with the deleted program don't lose any mass. In fact, they gain mass, due to renormalization.

It seems we don't just want to update on "not this hypothesis"; we want to explicitly model some sort of malignancy judgement (or more generally, a quality-of-hypothesis judgement), so that we can update estimations of how to make such judgements. However, it's difficult to see how to do so without creating a hierarchy, where we get a top level which isn't open to process-level feedback (and may therefore be malign).

Later, I'll present a Bayesian model which *does* have a version of generalization from feedback on hypotheses. But we should also be open to less-Bayesian solutions; it's possible this just isn't captured very well by Bayesian learning.

Prospects for Inner Alignment
-----------------------------

I view this more as a preliminary step in one possible approach to inner alignment, rather than "a solution to inner alignment".

If (a) you want to learn a solution to inner alignment, rather than solving it ahead of time, and (b) you agree with the framing of process-level feedback / feedback on hypotheses, and (c) you agree that we can't rely on a trusted meta-level to take process-level feedback, but rather need to accept feedback on "the whole process", then I think it stands to reason that ***you need to specify what it means to learn*** in this setting. I view the preceding sections as an argument that there's a non-obvious problem here.

For example, Stuart Armstrong has repeatedly [argued](https://www.lesswrong.com/posts/uL74oQv5PsnotGzt7/all-i-know-is-goodhart) that Bayesian learners can overcome many safety problems, *if only they're given the right prior information*. To the extent that this is a claim about inner alignment (I'm not sure whether he would go that far), I'm claiming that *we need to solve the problem of giving process-level feedback to a Bayesian learner* before he can make good on his claim; otherwise, there's just no known mechanism to provide the system with all the necessary information.

Anyway, even if we accomplish this step, there are still several other obstacles in the way of this approach to inner alignment.

1.  **Transparency:** It's unrealistic that humans can provide the needed process-level feedback without powerful transparency tools. The system needs to correctly generalize from simpler examples humans provide to the more difficult examples which a human can't understand. That will be difficult if humans can only label very very simple examples.
2.  **Basin of Attraction:** Because the system could use malign interpretations of human feedback, it's very important that the system start out in a benign state, making trusted (if simplistic) generalizations of the feedback humans can provide.
3.  **Running Untrusted Code:** A straightforward implementation of these ideas will still have to run untrusted hypotheses in order to evaluate them. Giving malign hypotheses really low probability doesn't help if we still run really low-probability hypotheses, and the malign hypotheses can find an exploit. This is similar to Vanessa's problem of [non-Cartesian daemons](https://www.lesswrong.com/posts/5bd75cc58225bf0670375575/the-learning-theoretic-ai-alignment-research-agenda#Taming_daemons).

Regardless of these issues, I think it's valuable to try to solve the part of the problem I've outlined in this essay, in the hope that the above issues can also be solved.

Summary of Desiderata
=====================

Here's a summary of all the concrete points I've made about what "learning normativity" should mean. Sub-points are not subgoals, but rather, additional related desiderata; EG, one might significantly address "no perfect feedback" without significantly addressing "uncertain feedback" or "interpretable feedback". 

1.  **No Perfect Feedback:** we want to be able to learn with the possibility that any one piece of data is corrupt.
    1.  **Uncertain Feedback:** data can be given in an uncertain form, allowing 100% certain feedback to be given (if there ever is such a thing), but also allowing the system to learn significant things in the absence of any certainty.
    2.  **Reinterpretable Feedback:** ideally, we want *rich hypotheses about the meaning of feedback,* which help the system to identify corrupt feedback, and interpret the information in imperfect feedback.
2.  **No Perfect Loss Function:** we don't expect to perfectly define the utility function, or what it means to correctly learn the utility function, or what it means to learn to learn, and so on. At no level do we expect to be able to provide a single function we're happy to optimize.
    1.  **Learning at All Levels:** Although we don't have perfect information at any level, we do get meaningful benefit with each level we step back and say "we're learning this level rather than keeping it fixed", because we can provide meaningful approximate loss functions at each level, and meaningful feedback for learning at each level. Therefore, we want to be able to do learning at each level.
    2.  **Between-Level Sharing:** Because this implies an infinite hierarchy of levels to learn, we need to share a great deal of information between levels in order to learn meaningfully.
3.  **Process Level Feedback:** we want to be able to give feedback about *how to arrive at answers*, not just the answers themselves.
    1.  **Whole-Process Feedback:** we don't want some segregated meta-level which accepts/implements our process feedback about the rest of the system, but which is immune to process feedback itself. Any part of the system which is capable of adapting its behavior, we want to be able to give process-level feedback about.
    2.  **Learned Generalization of Process Feedback:** we don't just want to promote or demote specific hypotheses. We want the system to learn from our feedback, making generalizations about which *kinds* of hypotheses are good or bad.

Initial Attempt: Recursive Quantilizers
=======================================

I'll give an initial stab at solving these problems, as a proof-of-concept. (Otherwise I fear the above desiderata may look like they're simply impossible.)

This is a formalization of the [recursive quantilizers](https://www.lesswrong.com/s/SBfqYgHf2zvxyKDtB/p/bEa4FuLS4r7hExoty) idea which I described previously.

A [quantilizer](https://www.alignmentforum.org/posts/5bd75cc58225bf0670375029/quantilizers-maximize-expected-utility-subject-to-a-conservative-cost-constraint) is a mild optimizer which avoids catastrophic outcomes with high probability, [averting Goodhart's Law](https://www.lesswrong.com/posts/5bd75cc58225bf06703750b1/another-view-of-quantilizers-avoiding-goodhart-s-law). It accomplishes this by refusing to 100% trust its value function. This seems like a good building block for us, since it significantly addresses "no perfect loss function."

A quantilizer requires a *value function, *$V$, which it mildly optimizes, and a *safe distribution, *$S$, which is a distribution over outputs which is assumed to have a low probability of catastrophic outcomes. It also requires an optimization parameter, $p$. The quantilizer $Q(V,S,p)$ mildly optimizes by randomly taking the top $p$*%* of outputs from $S$, as ranked by $V$. ($p$ can be derived from an estimate of the probability of catastrophe in $S$*,* combined with a level of tolerance for catastrophic risk.)

In line with our *learning at all levels* desiderata, we want to learn $V$, $S$, and $p$. Moreover, we'll produce all of these via quantilization, and recursively learn the inputs to all of those quantilizers as well.

In order to get *between-level sharing,* we will actually learn one big quantilization process which is equivalent to all those infinitely many levels.

Here's the setup.

In order to unify all the levels, I'll have quantilizers select *unified type for all arguments (UTAAs):* a tuple $(V, S, p, o)$ where $o$ is the object-level output we want out of the whole system (EG plans, strings of text, whatever). So now we understand the quantilization function $Q(a,b,c)$ to take 3 UTAAs. It will take the value function from the first, the safe distribution from the second, and the optimization parameter from the third. It then produces a UTAA. The user can take the object-level output of that UTAA as the result.*

What we want is a notion of *stationary distribution on UTAAs.* This is a distribution $D \in \Delta UTAA$ such that if we sample 3 elements from $D$, and feed those three elements into $Q$, the distribution on outputs of $Q$ is just $D$ again.

In effect, a stationary distribution $D$ is *all quantilized out*;  we can quantilize again, but it won't make any difference. So, we can just sample from $D$ and take the object-level output from the resulting UTAA.

This is very similar to the notion of stationary distribution for markov chains. The difference is that we have a *markov tree* instead of a chain.

![](https://39669.cdn.cke-cs.com/rQvD3VnunXZu34m86e5f/images/ddc09fadab6daef301d5d9b1fedb00502a112328a419f2bd.png)

So, just as finding the stationary distribution of a markov-chain monte carlo algorithm is similar to running the algorithm long enough that running it any longer is pointless, finding a stationary distribution for recursive quantilizers is like building a learning-to-learn hierarchy that's large enough that we don't get anything by going any further.

That's all well and good, but how are we supposed to find a stationary distribution we like? We can't just take a fixed point and hope it's useful and benign; there'll be lots of crazy fixed points. How do we steer this thing toward desirable outcomes?

Parameterizing Stationary Distributions
---------------------------------------

If a markov chain has multiple stationary distributions, we can parameterize them through a distribution on starting states. A distribution on starting states just means a probability of picking any one starting element, so this relationship is completely linear: by interpolating between different starting elements, we interpolate between the stationary distributions which those starting elements eventually reach.

We can similarly parameterize stationary distributions via initial distributions. However, we don't get the same linearity. Because we have to select many starting elements for the $3^n$ inputs to an $n$-level tree, and we select those elements as independent draws from the initial distribution, we can get nonlinear effects. (This is just like flipping a biased coin (with sides labelled 1 and 0) twice and sending the two results through an XOR gate: the probability of getting a 1 out of the XOR is nonlinear in the bias.)

This means we can't reduce our uncertainty over initial distributions to uncertainty over initial UTAA. (There may be some other tricks we can use to simplify things, but they probably aren't worth exploring in this post.)

So we *can* parameterize our uncertainty over stationary distributions via uncertainty over initial distributions. But, this is just turning uncertainty over one kind of distribution into uncertainty over another. What's the benefit of this?

1.  The set of stationary distributions is hard to know, but the set of possible initial distributions is clear. So this gives us an easy-to-work-with representation of stationary distributions.
2.  We know every stationary distribution is in the set, since we can start out in a stationary distribution.
3.  We can easily define the mapping from initial distributions to stationary distributions; it's just the stationary distribution you get by running things long enough, sampling from the given initial distribution. (Of course we may not get to any stationary distribution at all, but we can formally solve this by introducing a cutoff in program size, or through other devices.)
4.  We can therefore define learning: an update against a UTAA produces an update against initial distributions which produce that UTAA.

This is, of course, a very computationally intensive procedure. Unless better algorithms are found, the only way we can update is by producing a large quantilization tree (which we hope has converged) and running it many times to evaluate the outcome of a given initial distribution.

However, the resulting system has many marvelous properties. If we want to give feedback at any level in the hierarchy, we can convert this into feedback about UTAAs, and update our prior over initial distributions accordingly. For example:

*   We can label outputs as bad/incorrect by updating against all UTAAs which include those outputs.
*   We can give evidence about the value function over outputs, and convert this to an update about UTAAs based on the value function they contain. So, we can do value learning.
*   We can learn about the safe distribution over outputs. For example, one proposal for finding safe distributions is to model human behavior. Data-sets of human behavior could induce updates over UTAAs by checking how well a UTAA's proposed safe distribution fits the data.
*   At the same time, we can learn about the loss function by which we score safe distributions. If we have an update about this loss function, we translate it to an update about UTAAs by checking how a UTAA's value function *examines the safe distribution of another UTAA* when scoring it. Updating UTAAs based on this will, effectively, change the way safe distributions are selected in the second-to-last quantilization step. (Of course, it really changes *all* the quantilization steps, but when we anchor ourselves in how changes to the initial distribution alter our distribution on actual outputs, the easiest way to understand what's going on is to see this as a change to the second-to-last step.)
*   Similarly, we can learn about the loss function by which we score loss functions. So in the same system, we can directly learn from feedback, we can do value learning, and we can do meta-value-learning where we learn how to interpret evidence in value-learning.
*   Similarly, we can learn the safe distribution for meta-loss functions, the safe distribution over safe distributions, and on and on.
*   We can also allow process-level feedback by enabling UTAA value functions to examine the source code of other UTAAs (e.g. looking at how those UTAAs compute their value functions and safe distributions). We can teach UTAAs to detect suspicious code in other UTAAs and rate those UTAAs very poorly.

Wouldn't it be fascinating to be able to provide all those types of learning in one system?

Analysis in terms of the Criteria
---------------------------------

Let's examine how we did in terms of the criteria which I gave.

1.  **No Perfect Feedback:** This wasn't addressed directly, but might be indirectly addressed via #2.
    1.  **Uncertain Feedback:** I didn't specify any way to provide uncertain feedback, but it would be easy enough to do so.
    2.  **Reinterpretable Feedback:** I think this is a big failing of the approach as it stands.
2.  **No Perfect Loss Function:** Very significantly addressed by quantilization.
    1.  **Learning at All Levels:** Very significantly addressed by the recursive quantilization setup.
    2.  **Between-Level Sharing:** Significantly addressed. I didn't really talk about how this works, but I think it can work well in this setup.
3.  **Process Level Feedback:** Significantly addressed. The process which creates a given output is essentially the big tree that we sample. We can give any kind of feedback about that tree that we want, including any computations which occur inside of the value functions or safe distributions or elsewhere.
    1.  **Whole-Process Feedback:** Somewhat addressed. There is a question of whether the initial distribution constitutes a meta-level beyond the reach of process-level feedback.
    2.  **Learned Generalization of Process Feedback:** Significantly addressed. Process-level feedback can be given directly, as evidence against a specific UTAA, in which case there will be some generalization as we update against anything which thought that UTAA was a good idea. Or it could be given more indirectly, as general (level-independent) information about how value functions should judge UTAA. In that case there may be more generalization, as we update on how to judge UTAAs generally. (Or maybe not? An equivalence theorem about these different types of feedback would be nice.)

I think the most significant problem here is the lack of reinterpretable feedback. When we give feedback about something, we have to figure out how to translate it into an update about UTAAs (which can then be translated into an update about initial distributions). This update is fixed forever. This means the updates we make to the system aren't really tied to the value functions which get learned. So, for example, learning better value-learning behavior doesn't directly change how the system responds to updates we give it about the value function. (Instead, it may change how it interprets some other set of data we give it access to, as input to UTAAs.) This makes the "learning-to-learn" aspect of the system somewhat limited/shallow.

The second most significant concern here is whether we've really achieved whole-process feedback. I was initially optimistic, as the idea of stationary distributions appeared to collapse all the meta levels down to one. However, now I think there actually is a problem with the highest level of the tree. The initial distribution could be predominantly malign. Those malign UTAAs could select innocent-looking (but deadly) UTAAs for the next generation. In this way, the malign code could disappear, while achieving its goals by introducing subtle bugs to all subsequent generations of UTAAs.

The way I've specified things, trying to update against these malign UTAAs wouldn't work, because they're already absent in the stationary distribution. 

Of course, you could directly update against them in the initial distribution. This could eliminate select malign UTAAs. The problem is that this kind of process feedback loses generalizability again. Since it's the top level of the tree, there's nothing above it which is selecting it, so we don't get to update against any general selection behaviors which produced the malign UTAAs.

The only way out of this I see at present is to parameterize the system's beliefs directly as a probability distribution over stationary distributions.. You can think of this as assuming that the initial distribution is already a stationary distribution. This way, when we update against malign UTAAs at the beginning of the process, we update against them occurring at any point in the process, which means we also update against any UTAAs which help select malign UTAAs, and therefore get generalization power.

But this seems like an annoyingly non-constructive solution. How are we supposed to work with the set of fixed points directly without iterating (potentially malign) code to find them?

* * *

*: Actually, a UTAA should be a compact specification of such  tuple, such as a program or neural network which can output the desired objects. This is necessary for implementation, since EG we can't store V as a big table of values or S as a big table of probabilities. It also will allow for better generalization, and process-level feedback.