Remember the Caplan-Hanson Liberty v. Efficiency debate?  Robin stood firm for maximizing efficiency in all conceivable circumstances.  I argued, in contrast, that ethical reasoning should begin with simple cases and tentatively generalize:

Sensible moral reasoning begins with concrete, specific cases.  For example: It would be wrong for me to walk
over to Robin right now and punch him. 
From there, we can start to generalize. 
It would probably be wrong for me to walk over and punch any of the people in this room.  At the same time, we can note
exceptions.  If Robin had consented to
box me, then punching him would be
OK.  In fact, it would probably be wrong not to try to punch him, because I’d be
cheating you, the audience.

I’m awfully pleased, then, that Robin now writes:

Humans overwhelmed by the social complexities of helping a bum nearby
think they know enough about societies far away, so that ethics becomes
the main concern there.  I see the same thing in discussions of future
biotech or nanotech – ethics becomes the main frame, even though we
only have the faintest ideas of how future societies might integrate
those techs.  Beware the easy confidence of advising worlds far from
your knowledge or consequence.

Does this mean that Robin is giving up on dogmatic efficiency maximization?  I severely doubt it.  He’s tentative about knowledge and consequencesGiven knowledge and consequences, however, I bet that he still favors maximizing efficiency no matter what. 

My question: Why is Robin so humble about his factual knowledge, but so confident in his One Moral Principle?