Diplomacy

For thousands of years, diplomats have managed the relationship between tribes, cities, societies and countries.  Done well, diplomacy can prevent war, instil trust and spur prosperity.  But it can come at a cost, too.  When should diplomats lie, or conceal the truth?  How do the responsibilities of diplomats change as political authority moves from nations to other entities – like corporations and international bodies?  And what is ethical diplomacy?