Milton Friedman, the great economist, was one of a handful of intellectuals whose work forms the foundation for the modern conservative movement. He has been dead since 2006, but this week would be his centennial. He lived a long and prodigious life. In his lifetime, he was viewed as an odious figure by the Liberal brethren, a close advisor to dictators, an advocate of child labor, a favorite of fat cats.

Yet with the passage of time his repute as the prophet of an age of unsurpassed prosperity for just about everyone has only spread. Thus the Liberals have adopted a different tack. They adduce certain of his ideas to prove how dangerously cranky contemporary conservatives are. Even Milton Friedman did not go as far as Mitt Romney and the Tea Partiers, we are told.

“How Conservatives Misread and Misuse Milton Friedman,” reads a recent headline in the Washington Post above a piece by Nicholas Wapshott, which seems to argue that in Friedman’s great work “A Monetary History of the United States, 1867-1960,” written with Anna Schwartz, Friedman was arguing for inflating the American economy out of the Depression and presumably out of lesser recessions.

Needless to say it is a simplification, but it will serve a purpose with some Liberals. It helps to make Mitt Romney out as a harebrained radical for saying things like, “Milton Friedman understood what, frankly, our president, President Obama, I don’t think has learned even after three years and hundreds of billion of dollars in federal spending. And that is: Government does not create prosperity. Free markets and free people create prosperity.”

Mr. Wapshott, a sedulously reportorial former foreign editor of The New York Sun, appears in the unlikely role of what we increasingly see in this era of conservative recrudescence, a Liberal Body Snatcher. The Liberal Body Snatchers ghoulishly wait for a conservative leader to die and then they alight upon the speechless corpse and attribute to him sensible, prudent, and of course Liberal ideas. Sam Tanenhaus did it with the lifeless body of Bill Buckley. Mr. Wapshott apparently does it with Milton Friedman.

A whole gang of Body Snatchers has done it with President Reagan, arguing that he really was not that hawkish after all and never meant to challenge the USSR with force. He was all the while outmaneuvering such warmongers as Caspar Weinberger and Bill Casey and keeping things civilized for the likes of the editorial board of the New York Times and other Liberals who were so responsible for the peaceful conclusion of the Cold War. The Liberal Body Snatcher disfigures history.

Stephen Moore in the Wall Street Journal writes that Friedman “was the economist who saved capitalism by dismembering the ideas of central planning when most of academia was mesmerized by the creed of government as savior.” He was a tireless opponent of the state. In books and columns — most notably Newsweek in its heyday — he argued against state planning and for free markets.

I recall a longstanding debate between Milton and John Kenneth Galbraith, who at the time was billed as an economist but now is usually recognized as an elegant journalist. Galbraith mouthed the current wisdom. There was no free market, Galbraith claimed. He could not see it. He could not touch it. Today only an illiterate believes this. Free markets are observed allocating resources all over the world, even in India (until recently socialist), even in China (until recently communist). Only in places like the Obama White House is the state seen as a worthy replacement for markets.

Friedman argued abstruse economic questions and more general questions, for instance, the role of the state and the rule of law. He also had policies that he had worked out: low taxes, alternatives to Social Security, school vouchers, the volunteer military, and legalization of drugs. Taking him on was always hazardous. He was a cheerful and courteous advocate but deadly in debate. On the voluntary military his rejoinder to those who claimed he favored “mercenaries” was that they apparently favored “slaves.” I disagreed with him on the voluntary military and legalized drugs. Of course, history has proved him right on the military. Might it prove him right on drugs?

Mr. Moore ends his piece in the Journal by quoting Harvard’s Andrei Shleifer as describing the period from 1980 to 2005 as “The Age of Milton Friedman.” During it we “witnessed remarkable progress of mankind. As the world embraced free-market policies, living standards rose sharply while life expectancy, educational attainment, and democracy improved and absolute poverty declined.” I suppose a question worth asking in this election year is, are we finished with such progress or shall we begin “The Age of Milton Friedman” anew?

Mr. Tyrrell is editor in chief of the American Spectator. He is the author most recently of “The Death of Liberalism, published by Thomas Nelson, Inc.