Isn't the giant elephant in this room the whole issue of moral realism? I'm a moral cognitivist but not a moral realist. I have laid out what it means for my moral beliefs to be true - the combination of physical fact and logical function against which my moral judgments are being compared. This gives my moral beliefs truth value. And having laid this out, it becomes perfectly obvious that it's possible to build powerful optimizers who are not motivated by what I call moral truths; they are maximizing something other than morality, like paperclips. They will also meta-maximize something other than morality if you ask them to choose between possible utility functions, and will quite predictably go on picking the utility function "maximize paperclips". Just as I correctly know it is better to be moral than to be paperclippy, they accurately evaluate that it is more paperclippy to maximize paperclips than morality. They know damn well that they're making you unhappy and violating your strong preferences by doing so. It's just that all this talk about the preferences that feel so intrinsically motivating to you, is itself of no interest to them because you haven't gotten to the all-important parts about paperclips yet.

The main thing I'm not clear on in this discussion is to what extent David Pearce is being innocently mysterian vs. motivatedly mysterian. To be confused about how your happiness seems so intrinsically motivating, and innocently if naively wonder if perhaps it must be intrinsically motivating to other minds as well, is one thing. It is another thing to prefer this conclusion and so to feel a bit uncurious about anyone's detailed explanation of how it doesn't work like that. It is even less innocent to refuse outright to listen when somebody else tries to explain. And then strangest of all is to state powerfully and definitely that every bit of happiness must be motivating to all other minds, even though you can't lay out step by step how the decision procedure would work. This requires overrunning your own claims to knowledge in a fundamental sense - mistaking your confusion about something for the ability to make definite claims about it. Now this of course is a very common and understandable sin, and the fact that David Pearce is crusading for happiness for all life forms should certainly count into our evaluation of his net virtue (it would certainly make me willing to drink a Pepsi with him). But I'm also not clear about where to go from here, or whether this conversation is accomplishing anything useful.

In particular it seems like David Pearce is not leveling any sort of argument we could possibly find persuasive - it's not written so as to convince anyone who isn't already a moral realist, or addressing the basic roots of disagreement - and that's not a good sign. And short of rewriting the entire metaethics sequence in these comments I don't know how I could convince him, either.