Full Idea
The fact that people can and must react when confronted with another culture, and do so by applying existing notions, seems to show that ethical thought of a given culture can always stretch beyond its boundaries.
Gist of Idea
Our ability to react to an alien culture shows that ethical thought extends beyond cultural boundaries
Source
Bernard Williams (Ethics and the Limits of Philosophy [1985], Ch. 9)
Book Reference
Williams,Bernard: 'Ethics and the Limits of Philosophy' [Fontana 1985], p.159
A Reaction
Hardly conclusive, but it does seem to show that there is an element of universalising in values, no matter how local you may consider them to be.