which Jack Levy called “as close as anything we have to an empirical law in international relations.”I've written before about my skepticism about the whole notion that democracies will never fight each other. And that's what liberals are saying with this - if Jack Levy is correct, and it is close to an empirical law, then democracies should almost never fight each other, for the rest of time.
The law in question is not that democracies are more peaceful (by any measure, they most certainly are not), but rather that democracies do not fight each other.
I should concede that, in the 20th century, the evidence does suggest a fact of a democratic peace: There isn't an example of two democracies going to war in the 20th century. However...
There's a number of problems with this theory, but first I'd like to break it down a bit. The modern DP theory says that liberal and democractic states will not attack each other because a) a separation of political powers will prevent one ruler from making all foreign policy, b) "the marketplace of ideas" will prevent false of misleading information from being used as propaganda, and c) liberal states can implicitly trust one another's decision-making, thus making misperceptions less frightening.
All of these rules were disproven by the Iraq War, despite the fact that the victim country in this case was not itself a democracy. We can see that A is not true. The President of the United States, despite a nominal separation of powers, publicly stated that he would go to war without an explicit endorsement from Congress. Instead, Bush preferred to use the post-9/11 resolution. This was never tested, but it is difficult to see how the Congress would have seriously opposed Bush if he had chosen to go down that road. More broadly, we can see that in most democracies the head of government has immense power to direct foreign policy. Kosovo showed that the President, even with an opposition Congress, could mount a foreign military expedition.
B is also false. The "marketplace of ideas" failed, and badly. Every single claim used to justify this war was disproven before the war began. Period. Often, claims were disproven only hours after they were made. For the best summary of how badly the press failed in this regard, read Chaim Kaufmann's "Threat Inflation and the Failure of the Marketplace of Ideas." (warning-PDF)
Finally, C was shown to be questionable at best. There is little evidence to show that France or Germany were reassured by the Bush decision-making process. Again, parts of James Risen's State of War make this very clear. Democracies are just as prone to misperception as autocracies. For further evidence of this fact, see Vietnam War, 1964-72.
There are more fundamental problems with DP as a theory. They go deeper than the parts. The first problem is that it deals exclusively with war. This makes the theory nearly useless, because modern democratic states have numerous hostile options they can use in foreign policy short of war. Assassination, coups, embargoes, etc. For example, where do we put US actions against democratically elected leaders in Latin America? Allende was removed and US interests were served well short of a war, but it doesn't exactly reinforce any democratic peace.
The other problem is what I call the "War of 1812" problem. That is, how do we classify a democracy? The United Kingdom and United States of the era were hardly democracies by modern standards, but they still had all the elements that should have kept the peace (separation of powers, free press, similar decision making process.) It failed. We can either say a) that one or both countries was undemocratic, or b) the DP hypothesis is not, in fact, an empirical law. There are other examples of democracies going to war, notably from the Peloponnesian War. (Don't believe your crappy history books - Sparta had just as much democratic credibility as Athens, if not more so.)
We can only overcome this weakness to the theory is we say that countries need to be both liberal and democratic, but all this means is that countries who agree on the basic operating principles of the world are likely to get along. We could just as easily note that countries that are Communist and totalitarian (Mao and Stalin) get along, but not simply Communist (Mao and Khruschev.)
Finally, one other accepted rule to the democratic peace hypothesis is that a new or fragile democracy is actually more likely to be attacked. Ironically, this is meant to support the DP hypothesis, but it's actually the straw that breaks the academic's back. Where do we find new and fragile democracies, historically speaking? Generally in post-colonial or post-autocratic states. In post-colonial situations especially, there are powerful reasons for the old colonial power to try to intervene and reassert control. In post-autocratic states, a fragile government can be seen as an invitation by other states to intervene to either protect their own interests or expand their territory. We can see that the UK, the US, France, and Belgium have all intervened in post-colonial conflicts against democratic or popularly-supported governments. See Iran, Vietnam, Guatemala, Chile, Congo, etc.
So basically the "new democracy" exception really just justifies imperialism and colonialism. That is to say, rather than reinforcing the DP hypothesis, we've simply brought it back to realpolitik - the powerful will do what they want, and the weak endure the consequences.
I don't like the "realist" school of though, mainly because it's what has led to so much blood and pain in the post-WWII period. But blind liberalism in the Internation Relations sphere is dangerous too. We can't be reassured by blindly accepting that democratic states will agree with us, just because all the states that already agreed with us before happened to be democratic.