phrontist did an admirable job of providing a specific answer, but the answer to your question could be comprised of literally millions of works on philosophy, sociology and law throughout the ages. Can you narrow this down a bit? posted by I EAT TAPAS at 9:32 AM on May 12, 2012 [1 favorite]
This is a question in the philosophical subject called "Meta-ethics". One of the main questions of meta-ethics is: if there are moral truths, what makes them true? Is a morally wrong action wrong because God says so, or because of something intrinsic to the act, or because it causes suffering, or just because we have social conventions describing it as wrong?
It sounds like you're describing a view according to which moral truths are just true by convention - this kind of view is called "conventionalism". (Note that you could believe that convention is the whole story about all of morality, or you could believe that *some* moral truths are true for a deeper reason and *some* are only true by convention. I'm thinking that you are interested in the former.)
In that encyclopedia entry, you can read a little about the character Glaucon's account of morality in Plato's Republic, which is one version of the kind of view you describe. The article has a number of other points that might be of interest, and a link at the bottom to an extensive metaethics bibliography. posted by LobsterMitten at 12:49 PM on May 12, 2012
posted by phrontist at 9:17 AM on May 12, 2012 [1 favorite]