Paul, I think values and beliefs have both changed in that case - we (I hope I'm right to generalize!) don't judge that any facts about a person could make it right to enslave them. Most of us have scrapped the whole teleological framework Aristotle used to say that.

I probably should have said "...counts as the sort of moral progress Eliezer is talking about", the reason being that updating beliefs/instrumental values isn't a matter of metaethics, and is unproblematically directional.

Nominull, in your first sentence, does "people" mean everybody? In the second, what's the "right way of thinking"?

Unrelated: I think Michael makes an important point with "an ecosystem of godshatter".