Ooof, I have some trouble following this type of philosophical discussion. My mind tries to wrap itself around an answer and I just can't get it out properly.

I think we know what is right or wrong when we realize that we would or wouldn't want to happen to us. For example, when a child gets a toy taken away from him, he feels upset. He then know that taking a toy away from somebody else will make them feel upset. We tell the child it is wrong to take a toy away and he associates making a person feel bad as being wrong.