I certainly agree with most of Stefan's philosophical arguments, but i am struggling to agree with the concept of Universally Preferable Behavior (UPB). To make the statement, "There is no UPB," does not seem to violate UPB because it does not make a claim of behavior, but a claim of preference which is in itself not behavior. To know if there is in fact an instance of UPB, we would have to check every instance of the behavior and see that everyone prefers the same thing. I think George Boole's denial of existential import of universals is based on fairly good reasoning (we cannot know universals because we cannot check every instance of something). Of course, by definition some things are universals. For example, a fish is something that lives in water.
My second concern is with the presentation of the non-aggression principle. The NAP is by any account a good rule for any society to follow, but without the assumption in which to base it, it is a prescription without a foundation. Maybe it has foundation, but i am not familiar with the foundation of the argument in the philosophical form. What i mean by its foundation is that philosophers have to site their assumption for proposing an ought statement. Take for example Thomas Hobbes, his philosophy is based on the state of nature (life without government). What is the assumption when we use the NAP?