I’ve never seen a survey, but casual empiricism makes me think that economists are hawks. Arnold Kling calls himself a Jacksonian – “the patriotic fighters for whom the worst sin is not going to war, it’s losing one.” But even liberal Democratic economists strike me as pretty eager to settle international disputes by bombing enemies back into the Stone Age.

The use of force is easy to rationalize in terms of basic economics. “We should make them PAY for what they’ve done!” It’s just the law of demand: raise the price of crossing us, and fewer people will cross us. Make the price another Hiroshima, and perhaps the quantity demanded will fall to zero.

There is something to this line of argument, but it is too simple by far. Consider the following example. Suppose you go up to everyone you work with and tell them: “If you even think about getting in my way, you will be in a world of pain!” (Or as Marv puts it in Sin City: “And when his eyes go dead, the hell I send him to will seem like heaven after what I’ve done to him.”) You’re raising the price of getting in your way, right? So the predicted effect of this threat should be to make people treat you better.

That’s a crazy prediction. Making dire threats might scare some enemies off, but its primary effect would be to create new enemies. People who didn’t care for you before will now be out to getcha.

So why doesn’t the law of demand work in this situation? Threats and bullying don’t just move along the “demand for crossing you” curve. If your targets perceive your behavior as inappropriate, mean, or downright evil, it shifts their “demand for crossing you” out. Call it psychology, or just common sense: People who previously bore you no ill will now start looking for a chance to give you a taste of your own medicine.

The upshot for foreign policy is that people who warn about “sowing the seeds of hate” are not the simpletons they often seem to be. Military reprisals against, for example, nations that harbor terrorists reduce the quantity of terrorism holding anti-U.S. hatred fixed. But if people in target countries and those who sympathize with them feel the reprisals are unjustified, we are making them angrier and thereby increasing the demand for terrorism. Net effect: Ambiguous.

Not convinced? One story I heard soon after 9/11 is that Osama bin Laden was hoping that the American public would “Vote Yes for Lake Afghanistan.” (A popular t-shirt when I was a kid was “Vote Yes for Lake Iran.”) Anger at the decision to kill millions of Afghans in revenge for 3000 American deaths would galvanize the Muslim world (at minimum) and make recruiting more terrorists easy as pie. Was that bin Laden’s plan? I don’t know, but it could easily have worked.

Still not convinced? Try this thought experiment. Suppose the Israelis started executing the families of suicide bombers – men, women, and children. How sure are you that the quantity of suicide bombing would fall? It is more than plausible that this heinous policy would enrage the Muslim world, sparking more terrorism rather than less.

Economics is a great tool for solving social problems. After one semester of economics, for example, any decent student knows the solution to rush hour congestion: Raise the price of using the road! Unfortunately, achieving lasting peace is a lot harder than speeding up traffic.