If we search for an example of an empire which consisted of numerous different cultural, religious and language groups, and which nevertheless survived for a considerable length of time, we are invariably brought to the Roman Empire. This heterogeneous imperial formation apparently solved some of the major issues confronting the imperial form, and may therefore provide some insight for future developments of a larger than simply national societal grouping.
Sri Aurobindo observes: “But the imperial Roman had to face essentially the same problems as the moderns minus one or two very important complications and he solved them up to a certain point with a masterly success. His empire endured through several centuries and, though often threatened with disruption, yet by its inner principle of unity and by its overpowering centripetal attraction triumphed over all disruptive tendencies. Its one failure was the bisection into the Eastern and Western Empires which hastened its final ending. Still when that end came it was not by a disruption from within but simply by the decaying of its centre of life. And it was not till this central life faded that the pressure of the barbarian world without, to which its ruin is wrongly attributed, could prevail over its magnificent solidarity.”
The secret of the success of the Roman Empire lay in the fact that, although it conquered provinces and nations militarily and fused them together through military, economic and political force, it nevertheless took steps to encourage the internal unity of the empire and make of it a real, not simply a political, union. “It was this sense of separate nationality which the Roman rule succeeded in blotting out wherever it established its own dominant influence. And this was done not by the stupid expedient of a brutal force after the Teutonic fashion, but by a peaceful pressure. Rome first compounded with the one rival culture that was superior in certain respects to her own and accepted it as part of her own cultural existence and even as its most valuable part; she created a Graeco-Roman civilisation, left the Greek tongue to spread and secure it in the East, but introduced it everywhere else by the medium of the Latin language and a Latin education and succeeded in peacefully overcoming the decadent or inchoate cultures of Gaul and her other conquered provinces…. she not only admitted her Latinised subjects to the highest military and civil offices and even to the imperial purple, so that within less than a century after Augustus, first an Italian Gaul and then an Iberian Spaniard held the name and power of the Caesars, but she proceeded rapidly enough to deprive of all vitality and then even nominally to abolish all the grades of civil privilege with which she had started and extended full Roman citizenship to all her subjects, Asiatic, European and African, without distinction.”
Sri Aurobindo, The Ideal of Human Unity, Part I, Chapter 6, Ancient and Modern Methods of Empire, pp. 44-46