Every time there is a terrorist incident (or an attempted terrorist incident) in the United States, supporters and critics of more intrusive security measures engage in a form of intellectual dishonesty. Those who advocate greater security measures argue that they can carry out those measures without harming innocents. Those who criticize those measures argue that reducing surveillance carries no cost in reduced security. There are indeed some aspects of security that are, in effect, a free lunch. No one argues about the utility of putting in place security measures that carry zero risk of harming innocents. And eliminating ineffective security measures similarly requires no discussion.
The debate gets tricky — and this is where the intellectual dishonesty starts — when you have to make trade-offs between security and civil liberties. During the 2008 election campaign, candidate Barack Obama repeatedly argued that choosing between our values and our security is a false choice. In this, he was being unscientific. Whenever you are dealing with a foe that is hard to spot — whether it be a case of a rare but deadly flu or a would-be terrorist — there is always an inverse relationship between the number of false positives and the number of false negatives. Decreasing false positives tends to increase false negatives, and decreasing false negatives tends to increase false positives.
False positives are the innocent people we target during anti-terrorism measures, or patients who do not have a disease who get scanned, treated and exposed to side effects. False negatives are the terrorists who slip through, or the patients with real disease who go undetected. False negatives can have catastrophic consequences, but there are invariably many more false positives than false negatives, so the adverse consequences of false positives can sometimes be greater than the cost of false negatives. The recent call to scale back on screening for certain kinds of cancer is one example of how the toll of false positives can sometimes exceed the toll of false negatives.
When it comes to terrorism, a truly honest conversation would ask how many terrorist incidents a nation is willing to tolerate in order to maintain its highest values regarding civil liberties, or how many civil liberties it is willing to forsake in favor of security. The dishonesty lies in suggesting we can always reduce false positives and false negatives simultaneously: That is sometimes possible (when you develop a perfectly accurate and risk-free screening tool for terrrorism or disease) but more commonly you have to trade one off against the other.
Given the human penchant for wanting our cake and eating it, too, it isn’t surprising our national debate over terrorism falls into predictable and polarized camps, where each side demonizes the other’s views. Wouldn’t it be better to have an honest conversation about the costs of security, and the costs of civil liberties?
