I wonder, since it's important to stay pragmatic, if it would be good to design a "toy example" for this sort of ethics.
It seems like the hard problem here is to infer reasons for action, from an individual's actions. People do all sorts of things; but how can you tell from those choices what they really value? Can you infer a utility function from people's choices, or are there sets of choices that don't necessarily follow any utility function?
The sorts of "toy" examples I'm thinking of here are situations where the agent has a finite number of choices. Let's say you have Pac-Man in a maze. His choices are his movements in four cardinal directions. You watch Pac-Man play many games; you see what he does when he's attacked by a ghost; you see what he does when he can find something tasty to eat; you see when he's willing to risk the danger to get the food.
From this, I imagine you could do some hidden Markov stuff to infer a model of Pac-Man's behavior -- perhaps an if-then tree.
Could you guess from this tree that Pac-Man likes fruit and dislikes dying, and goes away from fruit only when he needs to avoid dying? Yeah, you could (though I don't know how to systematize that more broadly.)
From this, could you do an "extrapolated" model of what Pac-Man would do if he knew when and where the ghosts were coming? Sure -- and that would be, if I've understood correctly, CEV for Pac-Man.
It seems to me that, more subtle philosophy aside, this is what we're trying to do. I haven't read the literature lukeprog has, but it seems to me that Pac-Man's "reasons for actions" are completely described by that if-then tree of his behavior. Why didn't he go left that time? Because there was a ghost there. Why does that matter? Because Pac-Man always goes away from ghosts. (You could say: Pac-Man desires to avoid ghosts.)
It also seems to me, not that I really know this line of work, that one incremental thing that can be done towards CEV (or some other sort of practical metaethics) is this kind of toy model. Yes, ultimately understanding human motivation is a huge psychology and neuroscience problem, but before we can assimilate those quantities of data we may want to make sure we know what to do in the simple cases.
Perhaps the next step would be to add to the model a notion of second-order desire, or analyze a Pac-Man whose apparent terminal values can change when they're exposed to certain experiences or moral arguments.
Barring a major collapse of human civilization (due to nuclear war, asteroid impact, etc.), many experts expect the intelligence explosion Singularity to occur within 50-200 years.
That fact means that many philosophical problems, about which philosophers have argued for millennia, are suddenly very urgent.
Those concerned with the fate of the galaxy must say to the philosophers: "Too slow! Stop screwing around with transcendental ethics and qualitative epistemologies! Start thinking with the precision of an AI researcher and solve these problems!"
If a near-future AI will determine the fate of the galaxy, we need to figure out what values we ought to give it. Should it ensure animal welfare? Is growing the human population a good thing?
But those are questions of applied ethics. More fundamental are the questions about which normative ethics to give the AI: How would the AI decide if animal welfare or large human populations were good? What rulebook should it use to answer novel moral questions that arise in the future?
But even more fundamental are the questions of meta-ethics. What do moral terms mean? Do moral facts exist? What justifies one normative rulebook over the other?
The answers to these meta-ethical questions will determine the answers to the questions of normative ethics, which, if we are successful in planning the intelligence explosion, will determine the fate of the galaxy.
Eliezer Yudkowsky has put forward one meta-ethical theory, which informs his plan for Friendly AI: Coherent Extrapolated Volition. But what if that meta-ethical theory is wrong? The galaxy is at stake.
Princeton philosopher Richard Chappell worries about how Eliezer's meta-ethical theory depends on rigid designation, which in this context may amount to something like a semantic "trick." Previously and independently, an Oxford philosopher expressed the same worry to me in private.
Eliezer's theory also employs something like the method of reflective equilibrium, about which there are many grave concerns from Eliezer's fellow naturalists, including Richard Brandt, Richard Hare, Robert Cummins, Stephen Stich, and others.
My point is not to beat up on Eliezer's meta-ethical views. I don't even know if they're wrong. Eliezer is wickedly smart. He is highly trained in the skills of overcoming biases and properly proportioning beliefs to the evidence. He thinks with the precision of an AI researcher. In my opinion, that gives him large advantages over most philosophers. When Eliezer states and defends a particular view, I take that as significant Bayesian evidence for reforming my beliefs.
Rather, my point is that we need lots of smart people working on these meta-ethical questions. We need to solve these problems, and quickly. The universe will not wait for the pace of traditional philosophy to catch up.