A former classmate of mine who took a philosophy class told me that some people in his class, including himself, didn’t think there are objective moral values and duties. Why? Because different cultures have different opinions on what is right and wrong. The diversity between cultures and individuals seems to be a strike against an objective standard.
The problem is that this fact doesn’t lead to that conclusion. With any objective reality, people apprehend it differently and some people have a closer grasp of it than others do. If there is an objective or factual quality to moral values and obligations, then it wouldn’t be surprising that people apprehend it differently or have differing grasps of its content. It doesn’t show that it isn’t there.
This doesn’t solve all the problems of course. How do we know this reality? What form does it take? I can’t really answer these things right now, but I don’t find the above argument against objective moral values and duties convincing.