This is a great question!!
I was just thinking of this the other day. I used to think everyone had sort of an "in-born" sense of right or wrong, that co-incided with Bible principles. But lately, I've been noticing that alot of people don't. I don't know if it's just a lack of common sense or common courtesy, or what.
But, yes, bible principles would work for me. But I think there are some people who need them to be written down and applied for them, with consequences for not following, or they just don't get how to behave, how to treat others or what is fair.