&gt; but what are we supposed to do?<p>One rational response is that we know plenty of terrorist plots are foiled by intelligence agencies and police, so giving them more resources to act could be a logical thing to do. Similarly, improving communication between agencies and between countries might be helpful.<p>Most of that would not be publicly noticeable, so to the general public it might seem like &quot;nothing is being done.&quot; But that wouldn&#x27;t be the case.<p>What might <i>not</i> be rational is to change public policies, like foreign policy or domestic policy or immigration policy. Those might serve the role of theater, making the public feel that something is being done. But you also run the risk of being led along by the terrorists - the attacks might have been a provocation intended to elicit that response (do they want France to stop attacking them in Syria? Or to attack them more so they can more easily radicalize their followers? who knows). Instead, if we react rationally, it doesn&#x27;t matter what they intended.