LONDON — American philosopher and constitutional law expert Ronald Dworkin, a liberal scholar who argued that the law should be founded on moral integrity, has died at 81.

Mr. Dworkin died of leukemia in London early Thursday.

Mr. Dworkin was a professor of law at New York University and emeritus professor at University College London.

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He was one of the best known and most quoted legal scholars in the United States and an expert on British law.

NYU Law School dean Richard Revesz said he was ‘‘not only an intellectual giant, but also a masterful teacher, admired colleague, and beloved friend.’’

Mr. Dworkin was best known for the idea that the most important virtue the law can display is integrity, understood as the moral idea that the state should act on principle so each member of the community is treated as an equal.

Mr. Dworkin’s works included “A Matter of Principle” and “Justice for Hedgehogs.”

He argued that acting with dignity and moral clarity could make life worthwhile.

‘‘If we manage to live a good life well, we create something more,’’ he wrote. ‘‘We write a subscript to our mortality. We make our lives tiny diamonds in the cosmic sands.’’

Mr. Dworkin graduated from Harvard Law School in 1957 and was a Rhodes Scholar at Oxford University.

He told the Guardian newspaper two years ago that he did not know how to judge his life’s work.

“When I was a Wall Street lawyer, I realized I didn’t want that life. So I went and did what I found most fulfilling,” he said. “I can’t say if I’ve succeeded.”