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First, it will destroy, or at least severely weaken the middle class, since the society will be less and less able to create the surplus it needs to sustain itself. Second it will cause states to radically decentralize as they become less and less able to keep a complex bureaucracy. Eventually, the society will revert to a far more local and far less integrated organization.
This is likely to have complex consequences. To begin with, less established revivalist movements are likely to wither away as their social basis disappear. This will obviously be the case for such projects as Old Prussian revivalism which are basically intellectuals' hobbies, but movements with far more credentials are quite likely to go the same way. The Occitan movement comes to mind. It is particularly telling that my girlfriend, who came from an area where this language is spoken doesn't relate at all to it and associate “unfrenchness” not with her own most certainly Occitan speaking ancestors, but with the Basques. Having failed to create a strong local identity, the Occitan movement is probably doomed to become a footnote in history.
Things may go differently, however, in areas where this local identity has been established or maintained. As the nation-state become less and less adapted to a world of increasingly scarce resources, it will be replaced by more local forms of governance. These structures, whatever they may call themselves will need some kind of legitimacy, however. Americans look very fond of talking about secession despite being quite homogeneous culturally speaking. European, on the other hand, are very wary of it. A Free Vermont movement, for instance, would be unthinkable in France, and even in areas where independence could have some legitimacy, it is rarely claimed. The party I belong to, for instance, is adamantly against secession and demands only a large internal autonomy, similar to the one American states enjoy, within a federal Europe, and we are quite typical in that matter. Only extremists, or the very successful, fight for outright independence.
Yet some kind of independence is bound to come. The French state, as it exists today, simply cannot survive peak energy. At some point in the future local authority will take over even if they still pay lip service to a rump central authority. The problem is that without some kind of shared identity, those successor polities will be weak and likely to fight among themselves. This is probably what doomed, culturally speaking the lowlands sub-roman britons : their tribal identity still living but weakened by romanization they were subverted by Germanic speaking who converted them to their language and culture. Where some kind of ethnic identity has become mainstream – even in a non-nationalist way – as in Brittany, whoever inherits the power after the ultimate failure of the nation-state, is likely to emphasize it and to push forward the symbols and narratives developed by the revivalist movement. Contrary to the common opinion, this kind of polity is less likely to be authoritarian and warlike. As it will be able to rely upon a shared identity to mobilize its population and legitimate its rule, it won't have to use brute force. Besides, it will far less likely to engage in botched unification wars, even if , of course it will try and reconquer what it thinks to be its historical territory – which promises for interesting times around my own town.
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http://www.energybulletin.net/49837