The question of nationhood

I really enjoy travelling to other countries and meeting people of different cultures. To date, I have managed to visit 46 countries of very different historical backgrounds and current circumstances. The more I travel, the more I feel that one of the key questions of our age is: what is the nature of the nation state?
It seems to me that, in every nation state, there are minority groups that feel less allegiance to that state than the majority of citizens, either because they are not treated equally or more fundamentally because they do not really wish to be citizens of that state but instead of either another state or even of a state which does not yet exist.
This analysis begs several difficult questions: How do we define a nation state? Who decides whether a territory is to constitute a state? How do we deal with those who do not identify with the state?
This is how I open the latest essay on my web page.