Milton Friedman, who died last Thursday at the age of 94, was the greatest economist of the 20th century. This is a bold claim, especially to the many who would award this palm to John Maynard Keynes. But there can be no question that, “in the long run,” Friedman's accomplishments will be seen to have far exceeded those of his British co-practitioner of the dismal science.

I knew Friedman quite well. I have worked on his biography for the last six years and also had the opportunity to be in contact with him on other works I wrote, in particular on the Austrian free market economist Friedrich Hayek.

Friedman was the most brilliant man I have ever known. He was incredibly fast in his mental processes, and his verbal fluidity was incredible. He had a great sense of humor. Almost everyone who knew him personally loved him, whatever may have been their political or policy differences with him.

Friedman could be forthright in criticism. I once sent him an article I had written on the economist Paul Samuelson, and he let me know in no uncertain terms that he did not agree with it. Similarly, on another occasion, I sent him a draft of a chapter on the disposition of Hayek's work, and he also did not agree with it.

Friedman believed that complete frankness and honesty is the best way to help people, particularly students. The time I spent with him and the correspondence that he sent me are among my most treasured memories and possessions.

Friedman's political philosophy was libertarian – he considered maximization of human freedom to be the ultimate social objective. He was typically opposed to expansion of government at all times and in all places. He believed that government has an essential role to play, but he recognized that, far too often, government oversteps its appropriate bounds – human freedom, he believed, is maximized when government is minimized.

Friedman was a teacher at the University of Chicago for 30 years, and hundreds of students benefited from him there. He found his greatest influence as a societal wise man and scholar. As with so many others, I read his columns in Newsweek as a teen and young man and remember watching his “Free to Choose” television series in 1980. I remember after watching the series that I had a much better understanding of inflation – when the government prints more money at a faster rate than the economy grows.

Friedman was liberal on social issues. He favored the legalization of drugs and thought that abortion should be legal.

The most significant issue on which he worked on in recent years was school vouchers. He believed that a system of educational vouchers would lead to a renaissance in education and would particularly benefit African American and lower socioeconomic students generally, because vouchers would give them more choices in the schools they could attend.

Friedman opposed most welfare programs. He did so not primarily for reasons of cost, though he opposed them for this reason, but because contemporary welfare programs have the “negative effect of creating a different kind of culture and a different kind of human being,” he once said.

“If people are born into a world in which there are very few welfare supports, in which the culture is one that requires people to be responsible for themselves,” he told me in June of 2005, “there will be many fewer such people than if they are born into a society in which it is taken for granted that the government will come in and help them out.”

Friedman was a close adviser to presidents Nixon and Reagan. He served on the commission Nixon established to create an all-volunteer army. In the best tradition of libertarianism, Friedman opposed a draft except in times of war.

Friedman was even closer to Reagan than he was to Nixon. Indeed, Reagan's policies of a stable monetary policy, reduced tax rates, less regulation and less domestic government spending were straight from the economist’s playbook. What Friedman said of Reagan on Reagan's passing could equally well be said of him: “Few people in human history have contributed more to the achievement of human freedom.”