Patrick Porter writes about two contending visions of the Afghan insurgency:Burke is playing down the economic angle. But there is a certain tension, or tradeoff, between ‘power’/'politics’ and ‘tribal vendettas’/'ethnicity.’Identity can define allegiance, but not exhaustively. Calculations about power balances can wreck the whole day of cultural ties.In Afghanistan, it is more prudent, given the impermanence with which different power brokers...