LONDON (AP) ― 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 the age of 81.

His family said Dworkin died of leukemia in London early Thursday.

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

He was one of the best known and most quoted legal scholars in the U.S. and also an expert on British law.

NYU Law School Dean Richard Revesz said Dworkin was “not only an intellectual giant, but also a masterful teacher, admired colleague and beloved friend.” He called Dworkin the most important legal philosopher of his generation.

“He will be dearly missed by those of us who were lucky enough to know him and by the countless people who followed and admired his work,” Revesz said.

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.

A frequent contributor to the New York Review of Books, Dworkin’s own works included “A Matter of Principle,” ‘’Law’s Empire,” and “Justice for Hedgehogs.”

He argued in his writings 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.”

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

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

“I’ve tried to be responsible for my decisions and to make an authentic life,” he said. “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, thinking about, arguing for the things that are hard, important and rewarding. I’ve tried to do it well. I can’t say if I’ve succeeded.”

Professor Stephen Guest at University College London said Dworkin was “a cosmopolitan American who regarded London as his main home, and who knew how to enjoy things, especially music and art.”

He is survived by his wife, Irene Brendel Dworkin, his children, Anthony and Jennifer Dworkin, and two grandchildren.