Partial preferences and models

post by Stuart_Armstrong · 2019-03-19T16:29:23.162Z · score: 13 (3 votes) · LW · GW · 6 comments


  Re-inventing the wheel

Note: working on a research agenda, hence the large amount of small individual posts, to have things to link to in the main documents.

I've talked about partial preferences [LW · GW] and partial models [LW · GW] before. I haven't been particularly consistent in terminology so far ("proto-preferences", "model fragments"), but from now on I'll stick with "partial".


So what are partial models, and partial preferences?

Assume that every world is described by the values of different variables, .

A partial model is given by two sets, and , along with an addition map . Thus for and , is an element of .

We'll want to have 'reasonable' properties; for the moment I'm imagining and as manifolds and as local homeomorphism. If you don't understand that terminology, it just means that is well behaved and that as you move and around, you move in every direction in .

A partial preference given the partial model above are two values , along with the value judgement that:

We can generalise to non-linear subspaces, but this version works well for many circumstances.


The are the foreground variables that we care about in our partial model. The are the 'background variables' that are not relevant to the partial model at the moment.

So, for example, when I contemplate whether to walk or run back home, then the GDP of Sweden, the distance Voyager 2 is from Earth, the actual value of the cosmological constant, the number of deaths from malaria, and so on, are not actually relevant to that model. They are grouped under the (irrelevant) background variables category.

Notice that these variables are only irrelevant if they are in a 'reasonable range'. If the GDP of Sweden had suddenly hit zero, if Voyager 2 was about to crash into my head, if the cosmological constant suddenly jumped, or if malaria deaths reached of the population, then this would affect my walking/running speed.

So the set also encodes background expectations about the world. Being able to say that certain values are in an 'irrelevant' range is a key part of symbol grounding and the frame problem: it allows us to separate and as being, in a sense, complementary or orthogonal to each other. Note that human definitions of are implicit, incomplete, and often wrong. But that doesn't matter; whether I believe that worldwide deaths from malaria are in the thousands or in the millions, that's equally irrelevant for my current decision.

In comparison, the and the values are much simpler, and are about the factors I'm currently contemplating: one of them involves running, the other walking. The variables of could be future health, current tiredness, how people might look at me as I run, how running would make me feel, and how I currently feel about running. Or it could just be a single variable, like the monster behind me with the teeth, or the whether I will be home on time to meet a friend.

So the partial preference is saying that, holding the rest of the values of the world constant, when looking at these issues, I currently prefer to run or to walk.

Re-inventing the wheel

This whole construction feels like re-inventing the wheel: surely someone has designed something like partial models before? What are the search terms I'm missing?


Comments sorted by top scores.

comment by koreindian · 2019-03-23T18:39:11.530Z · score: 10 (2 votes) · LW · GW

Re: Reinventing the wheel

I don’t know of any slam dunk search term, but I suspect that the discussion you want to have surrounding partial preferences will contain mainly similarities to the work done on ceteris paribus laws. Particularly, if we aggregate the partial preferences of all moral agents, we will produce something like a moral ceteris paribus law, where we are holding the set Z of background variables “unchanged” (i.e. within a “reasonable” range of values). You might find the discussion around the justification of CP laws useful.

Additionally, I believe there must be some relevant work on the application to morality of modal logic and possible world semantics. I don’t have something to point to here, but it might be a worthwhile direction.

comment by avturchin · 2019-03-19T17:36:59.084Z · score: 4 (2 votes) · LW · GW

Side note: what do you think about preferences about preferences of other people?

For example: "I want M. to love me" or "I prefer that everybody will be utilitarian".

Was it covered somewhere?

comment by Stuart_Armstrong · 2019-03-20T08:20:11.715Z · score: 2 (1 votes) · LW · GW

Those are very normal preferences; they refer to states of the outside world, and we can estimate whether that state is met or not. Just because it's potentially manipulative, doesn't mean it isn't well-defined.

comment by avturchin · 2019-03-20T09:55:37.935Z · score: 2 (1 votes) · LW · GW

But they are somehow recursive: I need to know the real nature of human preferences in order to be sure that other people actually want what I want.

In other words, such preferences about preference have embedded idea about what I think is "preference": if M. will behave as if she loves me - is it enough? Or it should be her claims of love? Or her emotions? Or coherency of all three?

comment by johnswentworth · 2019-06-18T19:21:22.027Z · score: 2 (1 votes) · LW · GW

How does this notion of partial preferences differ from saying "preferences are determined by a causal net"? I.e., the y's would be the direct causal parents of a decision, and the z's everything else.

comment by Stuart_Armstrong · 2019-06-19T14:08:05.852Z · score: 2 (1 votes) · LW · GW

This differs, because the z are assumed to be in a "standard" range. There are situations where extreme values of z, if known and reflected upon, would change the sign of the decision (for example, what if your decision is being filmed, and there are billions being bet upon your ultimate choice, by various moral and immoral groups?).

But yeah, if you assume that the z are in that standard range, then this looks a lot like considering just a few nodes of a causal net.