Nobel laureate and professor Milton Friedman, at age 94, succumbed to heart failure on Nov. 16. While the man is gone, those of us who hold personal liberty as society’s highest end will always remember his steadfast support of the principles of personal liberty.

Friedman, above all, was an economist’s economist. During his professional life, his research on statistical techniques, consumption behavior and monetary theory became part and parcel of today’s accepted wisdom among economists. His research on monetary theory and the role of money in an economy has provided central banks worldwide with the knowledge, whether they use it or not, for monetary stability.

Friedman will surely be remembered for these intellectual contributions, but what he’ll be remembered for the most is his steadfast support for personal liberty. In 1947, he joined with Friedrich Hayek and 40 other free-market academics, mostly economists of international distinction, to form the Mont Pelerin Society. The Society’s founding purpose was to reduce the academic isolation among liberty-oriented scholars at a time when socialism was seen as the wave of the future.

The Mont Pelerin Society now boasts more than 500 members worldwide, eight of whom have been Nobel laureates. I’m proud to be a member.

Friedman’s first big step into public policy issues, as an indefatigable defender of personal liberty, came in his 1962 book “Capitalism and Freedom.” In it he argued that educational vouchers were the solution to poor education; free markets make racial discrimination more costly; government regulations are the primary sources for harmful monopolies; and Social Security is an unfair and unsustainable system. At the time these weren’t popular ideas, even seen as heresy, but today they are much more widely accepted.

In 1980, Friedman co-authored “Free to Choose” with his wife, Rose Friedman, which was written as a follow-up to his 10-part PBS series with the same name. Among the topics discussed: The Great Depression was not a failure of capitalism, as so often claimed, but a failure of government, mainly the Federal Reserve Bank and the U.S. Congress; our welfare system creates permanent wards of the state; and we should decriminalize drugs by treating abuse as a medical problem.

Friedman made a major intellectual contribution to the formation of a voluntary army. In testimony before President Richard Nixon’s commission on eliminating the draft, Gen. William Westmoreland said he did not want to command an army of mercenaries. Friedman interrupted, “General, would you rather command an army of slaves?” Westmoreland replied, “I don’t like to hear our patriotic draftees referred to as slaves.” Friedman then retorted, “I don’t like to hear our patriotic volunteers referred to as mercenaries. If they are mercenaries, then I, sir, am a mercenary professor, and you, sir, are a mercenary general; we are served by mercenary physicians, we use a mercenary lawyer, and we get our meat from a mercenary butcher.”

Whether one agreed or disagreed with Friedman, they found him to be a friendly, witty and tolerant person. My first encounter with him occurred during the mid-1960s while I was a graduate student at UCLA and he was a visiting lecturer. I’ve since forgotten my statement to him during a lecture, but I recall he had patiently replied, “Walter, you don’t really mean that,” and proceeded to show me why.

During my guest-hosting stints on the Rush Limbaugh show, Friedman was a guest on several occasions. His responses to caller questions demonstrated the real teacher in him — the ability to explain complex phenomena in a way that ordinary people can readily understand.

In terms of his scholarly output and worldwide contributions to ideas on liberty, Friedman was the 20th century’s greatest economist.

Walter E. Williams is a professor of economics at George Mason University.