Moreover, even if we could agree that we had perfect information for why the attacks happened — based upon the perpetrators’ words, and corroborated with official investigations — we won’t engage in honest self-reflection or change public policy in response.

First, no state wants to acknowledge that their policies, institutions, or culture might contain any flaws that could serve as primary motivations for terrorism. Politicians cannot accept any correlation between domestic or foreign policies and terror attacks. To do so would — the argument goes — assign some moral equivalence to “our” behavior and “their” behavior, and thus legitimize the goals and means of terrorism. Even on a societal level, the phrase “this is why the terrorists hate us” has become shorthand for especially glaring examples of America’s conspicuous consumption, gluttony, or sloth. But behind the jokes is pride that our founding fathers wanted us to have the freedom and opportunity to buy and consume and do whatever we like, without concerns as to how others might perceive this.

Second, even if we know the Tsarnaevs’ motivations drew primarily from American domestic or foreign policies, the United States will not subsequently alter them, since that would be perceived as making concessions to terrorists. The theory is that if a state reveals that it is vulnerable to coercion, terrorists will pocket that appeasement, sense weakness, and escalate their demands with additional attacks. …