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American policy toward China is defined by a debate between the ‘functionalists’ and the ‘strategists.’ This time last year, ‘strategists’ were being sidelined as impractical trouble-makers and the functionalists were ascendant. But China’s increased assertiveness over the past few months has changed the Barack Obama administration’s approach.  In the competitive and sometimes nasty world of international politics, strategists now hold sway and functionalists are increasingly on the defensive.

First things first: what do these two sides believe? Strongly supported by many Democrats, the functionalists are mostly economists, or those who focus on the benefits of the economic relationship. Usually...