your argument equates being good to the social contract. as seen in the republic the ring of gyges (probably spelling it wrong) would make a man under the social contract immune to others and therefore it would be better for him if he was not good. thereby, goodness by this model is COMPLETELY relative. your reference to human nature to attempt to fix this would not be accepted as a fix in the public square because human nature to the public can mean any number of things. (and it is not clear how this is to fix it anyway)