Nassim Taleb's The Black Swan doesn't say much about academic history, since it focuses mainly on economics and finance. But what it does say intrigued me.
Taleb thinks that much historical change happens through the kind of events he calls "black swans," that is, events that are in practice completely unpredictable but have very important effects. After such events, he says, we have a habit of going back and explaining why they were inevitable, but these "explanations" are really just stories we tell ourselves to make our world seem more predictable and controllable. As examples of historical black swans Taleb offers the outbreak of the Lebanese Civil War in 1975, which made him into a refugee, and the rapid rise and spread of Islam and the Arab empire. The thing that still bothers Taleb about the Lebanese war is that all the adults he knew -- he was from an elite Christian family, and one of his grandfathers was Interior Minister when the war broke out -- said it was impossible. Lebanon, they said, was a merchant society with an ancient tradition of tolerance where people would rather get rich than fight. They were wrong, and it seemed to him that the higher up people were in politics, the less they knew about what was going on. His grandfather kept saying the war would end in a few days (it went on for 15 years), whereas his grandfather's driver was much more pessimistic. Taleb has not trusted anyone in authority since. Nor does he ever seem to have felt that his new homes in London and New York were really any safer from spasmodic violence than Beirut was in 1975.
I don't know much about Lebanon, but I think the Arab conquests of the 7th and 8th centuries are a great example of a black swan. They were not predictable, and I do not think they are explainable in any detailed way. And they were important.
Likewise the establishment of the Mongol empire in the 13th century. Such events depend on the particular genius of leaders, the outcomes of chancy battles, or the loss of nails from certain horseshoes, and people who try to explain them in terms of shifting weather patterns or some other rational "cause" are pseudo-scientific charlatans.
But even if those events were random and ultimately inexplicable, that does not mean historians can't explain anything. One has to step back from the events themselves to the conditions that made them possible. Throughout ancient and medieval times, settled empires were at constant risk of being conquered by nomadic peoples. China, Persia, India and Rome had huge populations and great wealth, but they remained vulnerable to being overrun by bands of horsemen with only a tiny fraction of their resources. To defend themselves they collected brutal taxes, raised huge armies, and placed them in vast networks of fortifications, where thousands of heavily armed soldiers gazed across the emptiness where the nomads pastured their horses and camels. What was it about the organization of these two kinds of societies that made the settled people so vulnerable? Then, in the 1700s and 1800s, the situation so reversed itself that all the world's nomads were brought under the rule of people from cities. What changed in the 17th and 18th centuries to make any further conquests by nomads all but inconceivable?
These are the questions with which history, as an explanatory science, is concerned. The outcomes of battles and the rise and fall of particular empires are great material for stories, but only rarely do they illustrate the kind of long-term economic and social forces that a modern social scientist can hope to understand and predict. The best historical storytellers work at both levels, showing how the actions of men and women and the weird chances of fate shape events, and how people and events are constrained by the physical, economic, and social facts of their worlds.