Reading Kevin Drum's review of Tom Friedman, along with Matt Yglesias' follow-up, made me wonder: Why don't democracies go to war with each other? Will this always be the case? And, the other big question, why should we expect that countries with deep economic ties won't go to war with each other? (Friedman's cutely-named "Dell Theory of Conflict Prevention.") My brain's a bit sluggish today, but it's not obvious to me why Friedman's two peace theories should be true.

Uh, okay, let's take a whack at democracies first. I'm not sure it's entirely true that no two democracies have ever fought each other, but I'll agree with Jack Levy that saying democracies rarely do battle is "as close as anything we have to an empirical law in international politics."

So why is this? You could say, if you were a fluffy constructivist, that democracies refrain from clubbing each other's brains out because they share some "common identity". But this seems wrong, obviously "common identities" aren't even stable within democracies, as when, for example, the United States had its little civil war. Moreover, in the future, if every country in the world becomes a democracy, it's hard to think that they'll all share one stable "democratic" identity, as one might think the U.S. and Europe do now, for instance.

Alternatively, one could say that democracies represent people who no longer believe in crude and barbaric things like nationalism or honor, and the people in a working democratic society become the sort of people who believe in liberal law and order. Now that too seems wrong; certainly nationalism is on the rise in good voting countries like Japan, and as Frank Foer pointed out in How Soccer Explains the World, globalization is actually inflaming nationalist sentiment in many parts of the world. I don't think a world of democracies would be at all free from nationalism and war-mongering. Certainly the United States is not.

There are also various structural explanations. Democracies move at a torpid pace, with lots and lots of veto points, so there are all sorts of obstacles in the path to war. That depends, of course, on what kind of democracy you have; here in the United States the president has usurped the right to declare war over the years. And as Matt Y. points out, Bush saw no reason to listen to business interests who were against the war in Iraq. Certainly this political structure hasn't stopped democracies from going to war with non-democracies, so then there's no reason to think it would stop two democracies from fighting each other.

Perhaps you could say that since democracies are open and transparent, they are more likely to make rational estimates on how best to keep the peace and avoid conflict with each other. (Assuming that war is likely when one or both sides misestimate its chances for success.) Now true, the U.S. has shown in Iraq that miscalculation is hardly exclusive to non-democracies. On the other hand, the Iraq war shows that democracies have a hard time bluffing about war. Everyone could see the invasion of Iraq coming from a mile away; one could say it happened in part because Saddam Hussein did not respond rationally to it, as a democratic leader might have. This is the best explanation—that is, a weaker democracy, threatened by a stronger, would a) know it was weaker and b) do everything to avoid war because it would be constrained by public opinion—but hardly certain.

Meanwhile, there are a few factors, theoretically, that make it more likely that democracies would go to war with each other. Democracies often have inexperienced leaders. Elected politicians must think in the very short-term. Popular opinion can often be very wrong about the best course of action. (From all the polls I've seen, people think and care less about foreign policy, so it stands to reason that democratic foreign policy could often be worse than autocratic foreign policy, though in practice I don't know.) All these things could very well create miscalculation and conflict.

At any rate, I can't see any real reasons why democracies wouldn't go to war with each other. Presumably I've missed something. But if not, that means the question of why, historically, democracies haven't bloodied each other up is mostly due to the fact that democracies are a recent phenomenon, the bipolar structure of the Cold War made everything weird, and the ironclad law's just an aberration. Of course, I'm merely nitpicking the ludicrously strong claim about democratic peace theory: that democracies would never go to war with each other. Obviously anything is possible. The more pressing question is whether two democracies would simply fight each other less than other alternatives. On that, I have no clue, though it seems plausible. And oh yes, I was supposed to talk about economic interdependence. Well, this post is getting long, so I'll have to get back to that later...