This study raises that difficult and complicated question on a broad front, taking into account the expressions and attitudes of a wide variety of Greek, Roman, Jewish, and early Christian sources, including Herodotus, Polybius, Cicero, Philo, and Paul. It approaches the topic of ethnicity through the lenses of the ancients themselves rather than through the imposition of modern categories, labels, and frameworks. A central issue guides the course of the work: did ancient writers reflect upon collective identity as determined by common origins and lineage or by shared traditions and culture?