Milton Friedman had a message for China: To get rich, it must be free. It was 1988. The Soviet Union was tottering. Across Eastern Europe, the communist order was on the verge of collapsing. Trying to avoid its own demise, the Chinese Communist Party had taken small steps toward unshackling its economy from the state. But prices for food and other necessities were surging as a result, and the party’s reformers wanted advice. They invited Mr. Friedman — the Nobel laureate and champion of economic freedom — to Zhongnanhai, the walled compound in Beijing where the ...