Which of the following (if any) determine being Polish:
-- blood (genetics, DNA)
-- place of birth and/or habitaiton
-- culture, religion and/or language
-- personal preference/declaration
-- all of the above
-- some of the above (which?)
-- none of the above
-- something else?
Blood?I doubt it, as someone who is half Greek and half Polish I can tell you the nationalism is high in these countries but the blood isn't strong, nor is there an origin. Both were lands inhabited by tribes and overtime saw vast emigration and immigration, along with their borders disappearing and blending under countless empires. (Byzantium, Prussia, Russia, Austria, Roman, Ottoman- just to name a few). The blood is mixed, even though there are some genes which most Poles do hold in common which can be used as an identity. But don't expect to be homogeneous like Iceland, or Britain.
Place of birth?While the place you are born DOES play a factor, with the culture you're taught into, the society you're brought up in, your first nurtured/learned language indeed would play a big implement into being brought up Polish, along with getting a Polish education. While it would be wrong to deny Polish-American their ethnicity, more and more of Polish Americans are speaking the language less and knowing the culture and history less as they blend into the corporatist monoculture of the American melting pot...which I think is sad...
Culture, religion, language?Culture and language of course. Someone who speaks Polish clearly has a strong interest in the country and is most likely Polish since Polish isn't so much a universal language like French or English, and of course culture plays a big role. But again anyone can pick these things up and not have any heritage, but in terms of Poland (which isn't like Japan or France) most people who speak the language and celebrate the culture are Polish. After all 98% of Poland considers themselves ethnic Poles. As for religion, Catholicism exists everywhere and in terms of culture I think it belongs more to Italy...
Personal reference?Well if someone truly doesn't want to be Polish to the point where they deny their own heritage, then why would you want them on the train? Better to have a foreigner who loves Poland. But yes if someone does have heritage I think that is enough to make the declaration that they are Polish, regardless is they don't speak the language or culture (in my opinion that would make them less Polish, but that is debatable). However, for a foreigner to just wake up and say it? No. Maybe if they were citizens, had family, lived there for a long time and spoke the language.
Something else?Yes, they MUST drink wódka. ;-) jking....lol