The idea that everything changed on September 11, 2001, was always a conceit. It was a conceit not because it exaggerated the importance of the event, but, curiously, because it underestimated it. The attacks on New York and Washington, for all their terrible human cost, did not change much by themselves. They did, however, change the horizon of political possibility. The shock of that morning, followed by the endlessly repeated images of the collapsing towers and New York’s blasted downtown, shook the country from nearly a decade of complacency and gave politics a fresh urgency.