Everything Is Obvious_ _Once You Know the Answer - Duncan J. Watts [51]
HISTORY IS ONLY RUN ONCE
Given how well this quasi-experimental approach to learning works in everyday situations and professional training, it’s perhaps not surprising that our commonsense explanations implicitly apply the same reasoning to explain economic, political, and cultural events as well. By now, however, you probably suspect where this is heading. For problems of economics, politics, and culture—problems that involve many people interacting over time—the combination of the frame problem and the micro-macro problem means that every situation is in some important respect different from the situations we have seen before. Thus, we never really get to run the same experiment more than once. At some level, we understand this problem. Nobody really thinks that the war in Iraq is directly comparable to the Vietnam War or even the war in Afghanistan, and one must therefore be cautious in applying the lessons from one to another. Likewise, nobody thinks that by studying the success of the Mona Lisa we can realistically expect to understand much about the success and failure of contemporary artists. Nevertheless, we do still expect to learn some lessons from history, and it is all too easy to persuade ourselves that we have learned more than we really have.
For example, did the so-called surge in Iraq in the fall of 2007 cause the subsequent drop in violence in the summer of 2008? Intuitively the answer seems to be yes—not only did the drop in violence take place reasonably soon after the surge was implemented, but the surge was specifically intended to have that effect. The combination of intentionality and timing strongly suggests causality, as did the often-repeated claims of an administration looking for something good to take credit for. But many other things happened between the fall of 2007 and the summer of 2008 as well. Sunni resistance fighters, seeing an even greater menace from hard-core terrorist organizations like Al Qaeda than from American soldiers, began to cooperate with their erstwhile occupiers. The Shiite militia—most importantly Moktada Sadr’s Mahdi Army—also began to experience a backlash from their grassroots, possibly leading them to moderate their behavior. And the Iraqi Army and police forces, finally displaying sufficient competence to take on the militias, began to assert themselves, as did the Iraqi government. Any one of these other factors might have been at least as responsible for the drop in violence as the surge. Or perhaps it was some combination. Or perhaps it was something else entirely. How are we to know?
One way to be sure would be to “rerun” history many times, much as we did in the Music Lab experiment, and see what would have happened both in the presence and also the absence of the surge. If across all of these alternate versions of history, violence drops whenever there is a surge and doesn’t drop whenever there isn’t, then we can say with some confidence that the surge is causing the drop. And if instead we find that most of the time we have a surge, nothing happens to the level of violence, or alternatively we find that violence drops whether we have a surge or not, then whatever it is that is causing the drop, clearly it isn’t the surge. In reality, of course, this experiment got run only once, and so we never got to see all the other versions of it that may or may not have turned out differently. As a result, we can’t ever really be sure what caused the drop in violence. But rather than producing doubt, the absence of “counterfactual” versions of history tends