At the present time there are in Britain, in harmony with the five books of the divine law, five languages and four nations — English, British, Irish and Picts. Each of these have their own language; but all are united in their study of God’s truth by the fifth — Latin — which has become a common medium through the study of the scriptures.
— Bede, Ecclesiastical History, Book I Ch. 1
To the Romans, ethnicity was almost a sort of human dimension of the landscape, as immutable as a river or a mountain range. They delighted in crowding their maps with the names of more and more tribes and assigning each one with specific traits. Those traits, of course, could never change. No people ever went extinct or changed. Notably, ethnicity for the Romans had to do with where you came from, not necessarily your genealogy.
Of course, as the Roman Empire ended, many peoples changed, and sometimes changed drastically. Ethnicity was a mutable thing in late antiquity, a complex of law, language, traditions, and religion. The Romans were effectively blind to the processes of ethnogenesis and ethnocide going on around them, but they were happening, nonetheless. As the empire crumbled, the conflicts involved created (and destroyed) many ethnicities.
Some ethnicities arose from the military success of individuals or dynasties; dependent on continued military success, they could disintegrate as soon as that warlord met defeat. This sometimes operated on a truly massive scale, like the Hun confederation under Attila. Some rulers tried to create multiethnic societies, like Theodosius, who tried to turn Italy into a state with two ethnicities: one civilian, Roman, Catholic, and bound by Roman law, the other military, Gothic, Arian, and bound by Gothic law. Ultimately, however, that society fell to Justinian’s attempted reconquest of the West.
In Britain, there are four ethnicities, each defined by others while struggling to define itself:
- The Britons: The Britons imagine themselves both as Roman citizens and as the descendants of the island’s original Celtic tribes.
- The Saxons: The Saxons are divided between those who imagine themselves as Britons and defenders of Rome, and those who imagine themselves as part of a new warrior aristocracy.
- The Picts: The Picts imagine themselves as the inheritors of the island’s original Celtic tribes, unconquered and unbroken.
- The Irish: The Irish imagine themselves as a people united by the High King of Tara.
Geary, P. Barbarians and ethnicity. In Bowersock, G., Brown, P. & Grabar, O. (1999) Late Antiquity: A Guide to the Post-Classical World, The Belknap Press of Harvard University Press, Cambridge, MA.