AMERICANS BELIEVE that for every problem there is a solution. If we think and work hard enough, we believe we can solve every problem. Of course, we also live with the obdurate presence of contingency and uncertainty. We know that too, for we believe in Murphy's Law. But the media assume that this tragedy was avoidable and start blaming: the administrators were negligent despite the fact that their hands were tied. The gun store should never have sold firearms to Seung-Hui Cho. All relevant information concerning mentally ill persons should be known to the police and to gun store operators,...