Gregory Clark thinks that most economic historians, and virtually all economists, have been pretty hopeless at solving the really big puzzles of the modern world. He aims, he says, at producing a big history, in the tradition of Adam Smith’s Wealth of Nations or Karl Marx’s Das Kapital, whose purpose is to lay out a universal interpretation of the course of economic development that is both simple and compelling.

The central question around which Clark’s ambition rotates is this: Why, about two centuries ago, did some countries break out of a relatively low- or no-growth environment and begin to experience very fast rates of economic growth? This phenomenon, often referred to as modern economic growth, can more easily be described and quantified than actually explained. A related puzzle that occupies Clark is why, when this dramatic growth was taking place, did more countries not try to imitate it, and thus themselves experience continually advancing prosperity? What particular policies or institutions separated countries experiencing “modern economic growth” from those that did not or could not?