The Keynesian economist Nicholas Kaldor called Milton Friedman one of the two most evil men of the 20th century. (Friedman was in distinguished company.) The ‘scourge’ he inflicted on the world was monetarism, a product of what Kaldor called Friedman’s Big Lie – of which more later. Moral judgments aside, how does Friedman rank in the world of 20th-century economists? By common consent, he stands with Friedrich Hayek and John Maynard Keynes at the apex of his profession. All wrestled with the defining problem of their age: the radical economic and political instability of the 1920s and 1930s.

Their responses reflected their national situations. Keynes, economically secure and confident in Britain’s political aristocracy, turned to the state to provide the stability lacking in markets. Hayek, fleeing the hyperinflation of central Europe, saw the state as the cause, not healer, of economic disasters. Friedman, the aspiring son of Jewish immigrants, put his faith in the ‘land of opportunity, in which anything is possible’. Keynes, I think, was the greatest of the three because he invented a new branch of economics – macroeconomics – to explain how markets might fail spontaneously, whereas Friedman and Hayek simply added refinements to the story of how government interference could wreck spontaneously perfect markets.

It was natural enough for Friedman, a brilliant young scholar in search of an identity, to join battle with Keynes

Friedman’s genius was to repackage classical economics for conservative political use. His was a ‘creative conservatism’, writes Jennifer Burns, in the ‘first full-length biography of Friedman based upon archival research’. His 1956 essay ‘The Quantity Theory of Money – A Restatement’ is a good example of this. His economic work consisted of a series of fertile restatements of the core ideas of classical economics assembled as artillery against the assault of Keynesians and planners.

He conducted the war with such panache that monetarism has defined the economic policy of the past 40 years, just as Keynesian economics defined that of the previous 40.