"First, that implies there's some sort of authority - legal or otherwise - that determines "socially valuable."" There is. The opinions of other people in your

"First, that implies there's some sort of authority - legal or otherwise - that determines "socially valuable."" There is. The opinions of other people in your society - generally expressed via the ballot box in a democracy. All authority is, or should, derive directly from that source of truth. That's sort of what society is - everybody else. Hence why we have social judgments on what is appropriate - like banning guns and the death penalty - and why we have different countries to encapsulate different views on those social judgments (my country bans the former, yours likely doesn't - but we both take a dim view of marrying off 12 year olds, something other societies are quite relaxed about). There is no objective truth here. It's all a social creation by a set of people who have chosen to co-operate with each other and call themselves a country.