Imagine that a U.S. president is considering his options vis-à-vis a rapidly developing Iranian nuclear-weapons program. First, a science adviser comes into the room and predicts that if the Iranians take the following quantity of fissile material and compress it into a sphere of the following size under the following conditions, then it will cause an explosion large enough to destroy a major city. Next, a historian comes into the room and predicts that if external attempts are made to thwart Iranian nuclear ambitions, then a popular uprising will sooner or later ensue and force changes in government until Iran has achieved nuclear capability.
The president would be unwise to begin debating the findings of nuclear physics with his science adviser. Conversely, the president would be unwise not to begin a debate with the historian. This would likely include having several historians present different perspectives, querying them on their logic and evidence, consulting with non-historians who might have useful perspectives, engaging in introspection about human motivations, considering prior life experience, and so on.
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