To Profile or Not to Profile? A Debate between Sam Harris and Bruce Schneier

I recently wrote two articles in defense of “profiling” in the context of airline security (1 & 2), arguing that the TSA should stop doing secondary screenings of people who stand no reasonable chance of being Muslim jihadists. I knew this proposal would be controversial, but I seriously underestimated how inflamed the response would be. Had I worked for a newspaper or a university, I could well have lost my job over it.

One thing that united many of my critics was their admiration for Bruce Schneier. Bruce is an expert on security who has written for The New York Times, The Economist, The Guardian, Forbes, Wired, Nature, The Bulletin of the Atomic Scientists, The Boston Globe, The San Francisco Chronicle, The Washington Post, and other major publications. His most recent book is Liars and Outliers: Enabling the Trust that Society Needs to Thrive. Bruce very generously agreed to write a response to my first essay. He also agreed to participate in a follow-up discussion that has now occupied us, off and on, for two weeks. The resulting exchange runs over 13,000 words.

This debate was conducted entirely by email, without a moderator. While the gloves came off early, Bruce and I permitted one another to modify previous statements and to insert comments into each other’s text. This occasionally complicated matters—requiring further work from the freshly injured party—but the resulting exchange is more temperate than it would have otherwise been, as well as more complete. Of course, there is only so much ripping and mending that a linear conversation can accommodate. And, as readers will see, Bruce and I still occasionally talk past one another, grow a little prickly, and leave important issues unresolved. Despite its imperfections, I think the following debate is a good example of how two people with very different perspectives on a controversial topic can engage in a rational conversation.

SH: First, let me say how much I appreciate your willingness to engage on this issue, Bruce. Whether or not our views fully converge in the end, I suspect that readers will find this discussion useful.

There are many things in your essay that I’d like to respond to, but I don’t want us to just hurl op-eds at each other. My hope is that this will be a proper conversation. So rather than attempt to hit every point in each round, I think we should assume that we will keep turning the problem of terrorism over and over until we are both satisfied (or have killed our readers with boredom).

In the essay that got me into so much trouble with my fellow secular liberals, and in response to which you have now attempted an exorcism, I was addressing the problem of airline security. In fact, I was talking about only one aspect of airline security—the most visible part, where passengers and their luggage get screened for bombs and weapons by the TSA.

It is important to acknowledge the narrowness of this focus, and I hope you will agree that your bringing up Timothy McVeigh and the Unabomber in this context was misleading. Everyone passing through security at an airport is getting on an airplane. Consequently, when it comes to airline security, we are not merely faced with a generic threat of “terrorism.” When searching the bodies of passengers (either with back-scatter X-ray scanners, magnetometers, or pat downs), we are worried about the threat of suicidal terrorism.

In fact, the profile for airline security is even more specific—we are worried about suicide bombers who want to kill hundreds of people selected at random (i.e., the people who just happen to be on a particular airplane). Therefore, the terrorist knows that his intended victims are not directly responsible for whatever grievance he might have. We are not talking about anti-tax maniacs bombing a federal building, animal rights activists targeting laboratories, or unhinged Christians killing abortion doctors. We are talking about people who have a cause for which they are eager to die (and perhaps have their families die), and who believe this cause can be advanced by hideous acts of instrumental violence, in which truly innocent and uninvolved people are murdered.

So, to begin, I just want us to agree about this initial focus. I’m happy to explore related issues of terrorism and to even talk about security in general, but let’s stay on point for the moment and discuss the unique circumstance of screening passengers and their luggage at the airport.

Before I discuss what I think is wrong with your analysis, I want to see if we share the same background assumption about the reality of suicidal terrorism in the year 2012:

Imagine that a terrorist is attempting to board an airplane bound for a major city in Europe or the United States with a bomb strapped to the body of his four-year-old daughter. Let’s also assume that he is not some lone lunatic engaged in an inexplicable crime. Rather, he has a community of supporters behind him who have helped bring this terrible plot to fruition. A trained engineer made the bomb and showed him how to detonate it; another accomplice drove him and his daughter to the airport; even his wife gave her blessing and vowed to perform a similar act of terrorism with their son in the near future. The man has dozens of confederates who would have been willing, even eager, to take his place with a child of their own—and each of these people knows a score of others who fully support his aims. In fact, there are hundreds of thousands of people, in dozens of countries, who would actively support this man’s actions, if given the chance, and perhaps millions who would do nothing to dissuade him, even if they could. What are the chances, in your view, that this terrorist is Muslim.

BS: High.

But so what? You’ve proposed a correlation between being Muslim and being a terrorist. I could propose other correlations with terrorism: wearing a gun, carrying a certain kind of reading material, having a certain micro-facial expression, appearing on a particular government list, buying a one-way ticket, holding a passport from a particular set of countries. There’s no shortage of correlations.

You’ve gone further, though. You’ve advocating a nationwide security system with two tiers of security based on your correlation. What you’re missing is that your correlation is just a small piece of that complex system and, as such, you’ve skipped a lot of steps along the way.

Security is a trade-off, and requires some sort of cost-benefit analysis. What is the cost of your security system? What are the benefits? What, exactly, is your correlation? (TSA screeners can’t sort based on religion; they have to sort based on something they can detect. And since there’s no such thing as “looking Muslim”—it’s a belief system, not an ethnic group—they’re going to sort on something like “looking Arab,” whatever that ends up meaning.) Then, you’re going to have to analyze the resulting security system. How does it work, and how does it fail? What’s the false-positive and false-negative rate? (You’ll have to do some theoretical analysis, at the very least refuting current research.) Can your system be gamed? (You’ll need some experimental data with real-world TSA agents in real-world conditions. The last thing we want is a security system that can be defeated with a bottle of blonde hair dye.) You will need it to relate to other security systems. We only have a limited security budget. Is your security system better than other airport security options? How does it affect the other security systems already in place at airports? Would we be better off spending that money on some other aspect of airport security? Or something more general than airports? In my book Beyond Fear, I proposed a five-step process to think through some of these questions. There are other, more rigorous models. But security engineering requires something more than intuition.

Here’s another correlation, perhaps easier to understand. Pilots have long complained about being subjected to the same security as everyone else. They can crash the planes, for heaven’s sake. It’s just common sense. But you can’t actually sort on “being a pilot” at a security checkpoint; you have to sort on “wearing a pilot’s uniform” or “carrying a valid pilot ID.” So now the question becomes whether it makes sense to develop an unforgeable pilot ID, train TSA screeners in how to recognize that ID, and develop a separate set of screening procedures for people with that ID—or simply screen pilots like everyone else and ignore their whining. And this is where the analysis starts.

Your intuition on the efficacy of an airport profiling system is wrong. The psychology of security is complex, and there is a great deal of of research about how our brains systematically get security decisions wrong. This is an example of that. Profiling at airports gives us less security at greater cost.

SH: You have delivered a litany of concerns about profiling that are (in my view) easily answered. I do not think that the problem we are discussing—how to keep people from blowing up airplanes—is as recondite or as complicated as you make it out to be. It seems to me that there are many things you are pretending not to know—or pretending that other people can’t easily know—that make the problem of preventing terrorism reasonably straightforward.

And I am not proposing a mere correlation between extremist Islam and suicidal terrorism. I am claiming that the relationship is causal. There are many ways to see this, and not too many ways to credibly deny it (though Robert Pape keeps at it by skewing his data with the Tamil Tigers).

The first sign of a religious cause comes from what the terrorists say of themselves: al Qaeda and its sympathizers have not been shy about discussing their motives in public. The second indication is what they say when they think no one is listening. As you know, we now have a trove of private communications among jihadists. The fine points of theology are never far from their thoughts and regularly constrain their actions. The 19 hijackers were under surveillance by German police for months before September 11, 2001 (read Perfect Soldiers). Islam was all that these men appeared to care about.

And we should recall how other people behave when subjected to military occupation or political abuse. Where are the Tibetan Buddhist suicide bombers? They have the suicide part down, because they are now practicing a campaign of self-immolation—which, being the incendiary equivalent of a hunger strike, is about as far from suicide bombing as can be conceived. And where is that long list of Palestinian Christian suicide bombers you’ve been keeping in your desk? Now would be a good time to produce it. As you know, Palestinian Christians suffer the same Israeli occupation. How many have blown themselves up on a bus in Tel Aviv? One? Two? Where, for that matter, are the Pakistani, Iraqi, or Egyptian suicide bombers killing for the glory of Christ? These Christian communities are regularly attacked by suicidal jihadists—why don’t they respond with the same sort of violence? This is practically a science experiment: We’ve got the same people, speaking the same language, living in the same places, eating the same food—and one group forms a death cult of aspiring martyrs and the other does not.

As I’ve written elsewhere, it isn’t impossible to conceive of Tibetan Buddhists practicing suicide bombing or of Middle Eastern Christians practicing terrorism at the same rate as their Muslim neighbors, but Islam offers a doctrine of jihad and martyrdom that makes such behavior perfectly understandable. And, again, it is the reason that jihadists themselves give for their actions.

To read more:
http://www.samharris.org/blog/item/to-profile-or-not-to-profile