You are confusing common sense with common knowledge.
This is a very interesting discussion, hope it doesnt turn into a flame war.
I'll preface this by saying I really am not trying to bait anybody here.
If right and wrong is a matter of common sense, as determined by the individual, and as Enahs said may change as the person changes, why is it that certain things are always held right and others wrong? As an example, its a pretty much universal belief that murder is wrong.
I believe the stock answer (correct me if I'm wrong though) is that we developed the instinct not to kill our neighbour through a long process of social evolution.
One thing that has always nagged at me about that though: if it was simply a matter of social evolution, why havent we found any society, anywhere, (or even for that matter records of any society) that believed that killing the guy next to you is ok?This comment was edited on Sep 14, 19:38.