[Gil]

Extremely good thread mate.
I voted Ernest Gellner, mostly because of the silogism he uses to express the identification of "nationality":

1. "Two men are of the same nation if and only if they share the same culture, where culture in turn means a system of ideas and signs and associations and ways of behaving and communicating.
2. "Two men are of the same nation if and only if they recognize each other as belonging to the same nation. In other words, nations maketh man; nations are the artefacts of men's convictions and loyalties and solidarities. A mere category of persons (say, occupants of a given territory, or speakers of a given language, for example) becomes a nation if and when the members of the category firmly recognize certain mutual rights and duties to each other in virtue of their shared membership of it. It is their recognition of each other as fellows of this kind which turns them into a nation, and not the other shared attributes, whatever they might be, which separate that category from non- members.