Superforecasting: The Art and Science of Prediction

by Philip E. Tetlock

The cure for this plague of certainty came tantalizingly close to discovery in 1747, when a British ship’s doctor named James Lind took twelve sailors suffering from scurvy, divided them into pairs, and gave each pair a different treatment: vinegar, cider, sulfuric acid, seawater, a bark paste, and citrus fruit. It was an experiment born of desperation. Scurvy was a mortal threat to sailors on long-distance voyages and not even the confidence of physicians could hide the futility of their treatments. So Lind took six shots in the dark—and one hit. The two sailors given the citrus recovered quickly. But contrary to popular belief, this was not a eureka moment that ushered in the modern era of experimentation. “Lind was behaving in what sounds a modern way, but had no full understanding of what he was doing,” noted Druin Burch. “He failed so completely to make sense of his own experiment that even he was left unconvinced of the exceptional benefits of lemons and limes.”8 For years thereafter, sailors kept getting scurvy and doctors kept prescribing worthless medicine.