What we’re talking about is a conclusion by the 18th century Scottish philosopher David Hume that it’s impossible to derive an “ought” (how we should act) from an “is” (a fact about the world). He believed that what we should do in response to anything real depends on our values, which are an entirely personal and subjective matter. For example, if you’re a vegetarian and I’m not, given the objective fact of an omnivorous buffet we will make different decisions about what we should eat.
Unfortunately, this philosophical edict from two centuries ago has had the effect of reducing all morality to simple chocolate/vanilla choices, even in the modern world. No one in the western tradition today dares to use their personal moral intuition to judge members of other cultures lest they seem imperialist.
On one hand it’s good to be “enlightened” about the possible value of other cultures. On the other hand are we out of line for condemning so-called “female circumcision”? What about a social system that requires women to hide themselves? Is there any way that we can call that wrong without being arbitrary.
I think these are important questions and I hope that the larger discussion results in some good ways to approach them. It’s my curse as an enlightenment idealist to believe that hard problems can be solved by talking.