How should it be phrased then?
If he wants to talk about the difference between white people and everything else, he's referring to skin color, which is obviously not something you can choose unless you live in New Jersey. That's what it seems like he's talking about, although he's very unclear. The alternative is to assume he's referring to the categories his employer's human-resources department uses to classify people, which is unrelated to any meaningful definition of "ethnicity". Such primordialist confusions of sociological concepts (like ethnicity) and biological concepts (like "race") are better fit for Himmler and Mengele.
Simply put, "ethnicity" means "membership of a people". What a "people" is is, of course, up for debate, but the element of membership
necessarily involves choice. And, as it turns out, the cumulative result of studies on the nature of ethnicity since the 1960s (see, for instance, the useful overview by Eriksen) has given us the conclusion that the
only commonality between all "ethnicities"
is, in fact, the element of choice in membership. These people self-identify as Pathans, so they are Pathans. These other people self-identify as Kohistanis, so they are Kohistanis. The fact that making the choice to identify as a given ethnicity might involve other choices as well (acquiring
Romanitas would have involved, for instance, learning Latin) does not make it any less an artifact of choice.
This does not mean that ethnicity encompasses all modes of social identification; age is not an ethnic identifier, for instance, and while gender and class have at times made up elements of some ethnic identifiers, they do not constitute ethnic identifiers on their own. And, of course, ethnicity is layered: Thiudahad, king of the Italian Goths, saw himself as a Goth, a Roman noble, and a Tuscan landowner all at the same time in a noncontradictory fashion. A more simplistic version would be noting that a Chinese-American immigrant in Brooklyn might think of herself as being Chinese, American, a New Yorker, and a Brooklynite, all at the same time and with varying levels of importance.
EDIT: Apparently galdre
does think that human-resources departments have a better definition and understanding of the concept of ethnicity than do sociologists and anthropologists. That's rather cute.
)
