1.

The history of economic thought in the twentieth century is a bit like the history of Christianity in the sixteenth century. Until John Maynard Keynes published The General Theory of Employment, Interest, and Money in 1936, economics—at least in the English-speaking world—was completely dominated by free-market orthodoxy. Heresies would occasionally pop up, but they were always suppressed. Classical economics, wrote Keynes in 1936, “conquered England as completely as the Holy Inquisition conquered Spain.” And classical economics said that the answer to almost all problems was to let the forces of supply and demand do their job.

But classical economics offered neither explanations nor solutions for the Great Depression. By the middle of the 1930s, the challenges to orthodoxy could no longer be contained. Keynes played the role of Martin Luther, providing the intellectual rigor needed to make heresy respectable. Although Keynes was by no means a leftist—he came to save capitalism, not to bury it—his theory said that free markets could not be counted on to provide full employment, creating a new rationale for large-scale government intervention in the economy.

Keynesianism was a great reformation of economic thought. It was followed, inevitably, by a counter-reformation. A number of economists played important roles in the great revival of classical economics between 1950 and 2000, but none was as influential as Milton Friedman. If Keynes was Luther, Friedman was Ignatius of Loyola, founder of the Jesuits. And like the Jesuits, Friedman’s followers have acted as a sort of disciplined army of the faithful, spearheading a broad, but incomplete, rollback of Keynesian heresy. By the century’s end, classical economics had regained much though by no means all of its former dominion, and Friedman deserves much of the credit.

I don’t want to push the religious analogy too far. Economic theory at least aspires to be science, not theology; it is concerned with earth, not heaven. Keynesian theory initially prevailed because it did a far better job than classical orthodoxy of making sense of the world around us, and Friedman’s critique of Keynes became so influential largely because he correctly identified Keynesianism’s weak points. And just to be clear: although this essay argues that Friedman was wrong on some issues, and sometimes seemed less than honest with his readers, I regard him as a great economist and a great man.

2.

Milton Friedman played three roles in the intellectual life of the twentieth century. There was Friedman the economist’s economist, who wrote technical, more or less apolitical analyses of consumer behavior and inflation. There was Friedman the policy entrepreneur, who spent decades campaigning on behalf of the policy known as monetarism—finally seeing the Federal Reserve and the Bank of England adopt his doctrine at the end of the 1970s, only to abandon it as unworkable a few years later. Finally, there was Friedman the ideologue, the great popularizer of free-market doctrine.

Did the same man play all these roles? Yes and no. All three roles were informed by Friedman’s faith in the classical…