This tribute is part of a series of reflections from HLS faculty, staff and alumni on the 15th anniversary of 9/11. View all tributes.

Contributor: Adrian Vermeule ’93

Adrian Vermeule ’93 is the Ralph S. Tyler, Jr. Professor of Constitutional Law. He is the author or co-author of eight books, including most recently “The Constitution of Risk” (2014) and “The System of the Constitution” (2012).

“Thanks largely to initiatives by Presidents of both parties, American law and policy has adapted flexibly to the new environment, trading off some liberty for greater gains in security.”


9/11 and its aftermath brought to the surface two distinct conceptions of what rationality requires in law and public policy. On one conception, the antonym of rationality is emotionalism, and the great evil to be avoided was formulating new counterterrorism policies under the influence of “fear” or “hate.” The mantra was that “if we change X because we are afraid of terrorism, then the terrorists win.” On a different conception, the antonym of rationality is failure to take account of new evidence. Fear may spur the adaptation of policy to changing circumstances, and may in that sense be beneficial. By and large, the second conception has prevailed. Thanks largely to initiatives by Presidents of both parties, American law and policy has adapted flexibly to the new environment, trading off some liberty for greater gains in security. This isn’t to say that all post-9/11 policy changes have been optimal, by any means. But at least we have avoided the trap of adopting a paralytic posture out of an excessive fear of acting fearfully — the fundamental error of phobophobia.