The questions is what you should care about.
Is it rational to care more about being able to predict accurately than care about inadvertantly doing evil?
Hah, looks like someone went through and upvoted all your posts in the conversation while downvoting mine. Relativism has at least one anti-fan :P
I didn't understand your last reply, but I'd still like to ask you a favor: imagine what the universe would look like if there weren't any particular best morality, only moralities that were best by some individual's standard, which nobody else was under any particular cognitive necessity to accept. All the electrons would stay in their orbitals, things would look the same, but inside agents would just do what they did for their own reasons and not for others.
Okay, thanks.
Derek Parfit has published his second book, "On What Matters". Here are reviews by Tyler Cowen and Peter Singer.