Bryan Caplan's pacifism

Bryan Caplan and several of his colleagues at GMU are engaged in a debate over Dr. Caplan's espousal of pacifism. If you want to follow it in detail, head on over to EconLog and Marginal Revolution. In his latest post on the subject, Dr. Caplan challenges his interlocutors to attack his premises, which he helpfully spells out here:

1. The immediate costs of war are clearly awful.  Most wars lead to massive loss of life and wealth on at least one side.  If you use a standard value of life of $5M, every 200,000 deaths is equivalent to a trillion dollars of damage.

2. The long-run benefits of war are highly uncertain.  Some wars - most obviously the Napoleonic Wars and World War II - at least arguably deserve credit for decades of subsequent peace.  But many other wars - like the French Revolution and World War I - just sowed the seeds for new and greater horrors.  You could say, "Fine, let's only fight wars with big long-run benefits."  In practice, however, it's very difficult to predict a war's long-run consequences.  One of the great lessons of Tetlock's Expert Political Judgment is that foreign policy experts are much more certain of their predictions than they have any right to be.

3. For a war to be morally justified, its long-run benefits have to be substantially larger than its short-run costs.  I call this "the principle of mild deontology."  Almost everyone thinks it's wrong to murder a random person and use his organs to save the lives of five other people.  For a war to be morally justified, then, its (innocent lives saved/innocent lives lost) ratio would have to exceed 5:1.  (I personally think that a much higher ratio is morally required, but I don't need that assumption to make my case).

My fifteen months in Baghdad were more than enough to convince me of 1), but I think 2) is suspect and my attack on it will call the usefulness of 3) into question.

Dr. Caplan is right that the long-run benefits of war are highly uncertain, but he does not go far enough. 2) is a specific case of a general principle: the long-run consequences of any act are uncertain, with the uncertainty increasing as the complexity of the system rises. As Yogi Berra put it, predictions are hard, especially about the future.

Let's reduce it to a system of two: a man and his wife. If he's mean to his wife, she will probably leave him, and if he is kind to her, she probably won't. But even here, uncertainty exists- perhaps his cruelty will trigger a perverse reaction in her and compel her to stay, or perhaps she will interpret his kindness as weakness and feel contempt for him, leading her to leave him. We can certainly adopt "be kind to your wife" as a general principle, because we know that most people prefer kindness to cruelty, but even in a system with two people and two possible outcomes, uncertainty exists.

When we scale up, the uncertainty gets much, much worse. The truth is that we have essentially no idea what consequences our actions may have a hundred or more years hence. The Srebrenica massacre can be plausibly traced back to King Philip V of Macedon's involvement in the Second Punic War- without Macedonian involvement the Romans wouldn't have come; had the Romans not come the region wouldn't have been Christianizied; had the region not been Christianized there wouldn't have been any religious divide between the Muslims and the Christians in 1995. And of course on the road to that massacre we have many, many other pieces that had to fall into place- Constantine's conversion, Muhammed's victories over the Meccans, the defeat of Heraclius at Yarmouk, the defeat of Romanos IV Diogenes at Manzikert, the Turkish victory over the Serbs at Kosovo, and so on, and so on.

History is replete with examples of wars that have had known, positive consequences. Had Pilsudski rolled over on the Vistula, the Red Army might easily have marched all the way to the Rhine, if not the English Channel. I am sure Dr. Caplan, curator of a Museum of Communism, needs no further details on what horrors would have followed in its wake. Had The Hammer fallen in defeat at Tours, "perhaps the interpretation of the Koran would now be taught in the schools of Oxford, and her pulpits might demonstrate to a circumcised people the sanctity and truth of the revelation of Mahomet." Choosing between 8th Century Islam and 8th Century Christendom, I would of course have chosen Islam, but today I much prefer what remains of Christendom to what has become of Islam. Had Themistocles not fought at Salamis and Leonidas at Thermopylae, the fires just starting to burn at Athens might have been snuffed out, and we could all be far, far worse off today.

Or we could be much better off. Perhaps the Persian state, with its cosmopolitanism, would have endured and sheltered the light of science and reason starting to glow around the Ionian Sea from the buffets of war, religion and conquest, and we'd all be teleporting to work by now. Who knows? Not me, and not Dr. Caplan. So when we are weighing a war (or any action), we will be paralyzed by doubt if we make the long-run consequences the standard by which we judge our choices. Perhaps in invading Iraq we inadvertently killed the child who would have grown up and cured cancer. Or, perhaps, we killed ten future Hitlers. Perhaps the historical dominos will fall in such a way that our intervention in Libya will be seen by future historians as a great turning point in human history, leading to an age in which tyrants are not tolerated and the civilized nations of the world extirpate any governments that terrorize their people. Or, perhaps, we are sowing the first seeds of an instability that will later lead us to World War III. Who knows?


We cannot know the long-run impact of our decisions, but we can make a pretty solid stab at the short-run impact. Forgive me if I am bragging, but I was pretty much on the money in my predictions of the short-run consequences of invading Iraq. The long-run jury is still out, but the violent resistance and ethnic/religious conflict I foretold in LiveJournal posts of yore all played out as I predicted. (Go me!) What's more, I was hardly a lone voice in the wilderness; many, many people were making the same arguments. Our leaders at the time were, unfortunately, acting out of a fatal combination of ignorance and arrogance. Their ignorance of the history of Iraq led them to make bad estimates of the short-run impact, and their arrogance led them to lend too much weight to their long-run predictions. With a combination of knowledge and humility, we can, I believe, make better decisions regarding war and peace, not lending undue credence to our long-run fantasies (or nightmares) while simultaneously making respectable guesses at what the short-run future will bring.

I think Dr. Caplan's first premise is enough to create a very strong presumption against war, and simultaneously serves as a good reason for us to govern our actions in such a way as to avoid making war likely. But sometimes the Mongols do come swarming off the steppe, and when they do the only decent thing to do is to man the ramparts and drive them off.