An excellent article, and I ultimately agree with the concluding premise. However, if I may (and because I know you so well and just cant resist), I would like to play devil’s advocate on your historical examples.
You at one point say “The most dynamic societies in history — the ones which invented machines, wrote classic books, prevented war — were relatively multicultural.” I believe that, in many respects, to be true. Rome’s strength was, indeed, that at some point it successfully incorporated the subjugated/allied nations into the “idea of Rome”, and particularly the Military, was an event which helped it to last so long, especially as the later Roman Emperors were no longer Italian. However, at the same time, it is interesting that Rome was very reluctant to do so. Augustus denied his wife’s request to extend citizenship to a handful of Guals who had provided worthy service to Rome on the grounds that it would debase the value of Roman Citizenship. Every new cult that diverging from Roman ideals of society, from Isis to Magna Matar, was initially mocked and resisted by the Roman Aristocracy (who frequently complained of the abandonment of traditional value. That is, after all the entire opening of Livy’s great history). Indeed we might say then that Rome became multicultural only over multiple generations and, in many respects, despite its best intentions to the contrary. Even then, multiculturalism was always on Rome’s terms. One could worship whichever deity they wanted and practice whichever ethnic traditions they wanted, so long as they did not diminish the uniting idea of “Rome”. The classic example of this is the Christian Persecutions, where the largest complaints by the Pagan Romans was that the Christians (unlike everyone else) were not willing to compromise their belief to worship the Emperor and the traditional gods who maintained the health of the Empire and its society.
We can make a similar argument about the Athenians, who despite their vaunted accomplishments strictly limited the rights of citizenship to only those males born of 2 Athenian Citizens. For the Greeks, the Barbarians (anyone who was not Greek or, ultimately Greekish) were always viewed as the “other,” and by extension weak, effeminate, unmanly (to the Greek idea of manhood). Indeed, one of their finest artistic representations, the Elgin Marbles of the Parthenon, depicted the triumph of the Greeks over these foreign “Barbaric” forces of “disorder” (Troy, the Amazons, Centaurus Giants) (although, ironically, the Greeks also had a healthy fascination/obsession with the different Amazons too, entirely because of this otherness). Then of course, we come to Alexander, who began to have problems with his Greek soldiers when he began to adopt Persian trappings of government and to encourage a hybrid Peso-Greek society. The same can be said of the Early Calphate, who welcomed Christians and Jews, but still placed strictures over their roles in society and made it abundantly clear what the national ideal/identity was. What then are we to make of these multicultural societies that, on closer observation, have some very mono-cultural views of society and their interaction with the world?
Of course, we can turn to your counter examples too. The Crusades, initially a response to the Muslim destruction of the Church of the Holy Sepulcher by a very monocultural Muslim Caliph, are hailed for introducing different ideas and foods to Europe, both through the experience of the Crusaders as well as the reopening of trade with the East, thereby helping to make it more multucultural. The Mongol Conquerors (although not without their own clash of cultures), e nevertheless adopt many of the elements of local culture into their ruling societies. After all, the great Kublai Khan (the grandson of Ghengis, of Marco Polo and Coleridge fame) and the entire Mongol Yuan Dynasty he founded adopted many Chinese cultural trappings and is considered one of the great Golden Ages of Chinese culture. The same can be said of the subsequently Muslim Illkhanate (founded by another Grandson of Ghengis), which continued to build upon the intellectual legacy of Persia, as well as the Khanates of Central Asia, which also became Muslim and engaged in similar multicultural practices. What then are we to make of the fact that these supposed monocultural civilizations were, in some ways, more open to multiculturalism in adopting their local traditions and ideas than multicultural Rome and Greece?
As to your statements about cities, I think that they generally do serve as melting pots that facilitate a multicultural exchange. That said, I also think that they provide their own impediments to multiculturalism in some ways as well. Rome was engine of the empire, at least for a few centuries. However, the great mixing bowl of the Roman empire was less cosmopolitan Rome than it was the multicultural army composed of Roman citizens and allies from the various provinces of the Empire and from different backgrounds. It is interesting that some of Rome’s most famous Emperors (Tragan Hadrian both from Spain and Septimus Severus from Syria, being some of the stand outs, especially as Septimus granted universal citizenship) ultimately had few cultural connections with the Capital and rose almost entierly through their military service. Indeed one, a soldier of Balkan descent declared Emperor in Britain by the name of Constantine, ultimately abandoned Rome for his own venue in Constantinople. In light of this development, is tempting to say that, had it been left to the Roman Aristocracy, we would never have moved far beyond Augustus’s aversion to foreigners.
It is also interesting that the epicenters of the American Revolution you cite (at least in the case of NYC and Philly) were actually some of the most Royalist cities there were, and therefore some of the most resistant to its ideals (not that such a stance has anything to do with multiculturalism either way). Indeed, in the case of the American Revolution (as opposed to the French), it is interesting how much support the Revolution (and the subsequent constitution) got from the landed aristocracy (Washington, Jefferson, Adams, Henry, and Hamilton’s father in law were all landowners, though Adams was a bit more cosmopolitanism). Likewise we can also observe that the hot bed of revolutionary activity was really the small New England towns, rather than the great cities. There is a reason Jefferson believed that the future of Republic lay in small towns and citizens of Yoman Farmers (something we forget in taking him as the villain in the recent musical about the Founder who had a more urban view of the future of America).
This example, of course, are very different from, say the French Reign of Terror during their Revolution, where the cosmopolitan Enlightenment elite strove for their own form of monoculture based on an exclusion of any idea contrary reason and dedication to the ideals of the Republic. Nor should we forget that it is cosmopolitan San Francisco that ultimately facilitated the Chinese Diaspora (I highly recommend the documentary in Search of General Tsao) by excluding them from holding property because of its aversion to their perceived otherness (and a false rumor about poisoning the water, but that is another aside). What then are we to make of the fact that, at least in these instances, the country and towns were better at facilitating cultural exchanges or openness to new ideas than the cities?
Anyway, just a few thoughts. Well done on the article ;o)