We can argue about rights and justice forever, but we are bound together by two more basic things. First, we are bound together by the ups and downs of the human experience. We all want to be happy. None of us wants to suffer. Second, we all understand the Golden Rule and the ideal of impartiality behind it. Put these two ideas together and we have a common currency, a system for making principled compromises. We can agree, over the objections of our tribal instincts, to do whatever works best, whatever makes us happiest overall.
