Superforecasting: The Art and Science of Prediction

by Philip E. Tetlock

To demonstrate the limits of learning from lectures, the great philosopher and teacher Michael Polanyi wrote a detailed explanation of the physics of riding a bicycle: “The rule observed by the cyclist is this. When he starts falling to the right he turns the handlebars to the right, so that the course of the bicycle is deflected along a curve towards the right. This results in a centrifugal force pushing the cyclist to the left and offsets the gravitational force dragging him down to the right.” It continues in that vein and closes: “A simple analysis shows that for a given angle of unbalance the curvature of each winding is inversely proportional to the square of the speed at which the cyclist is proceeding.” It is hard to imagine a more precise description. “But does this tell us exactly how to ride a bicycle?” Polanyi asked. “No. You obviously cannot adjust the curvature of your bicycle’s path in proportion to the ratio of your unbalance over the square of your speed; and if you could you would fall off the machine, for there are a number of other factors to be taken into account in practice which are left out in the formulation of this rule.”8