Ronald Dworkin, a legal philosopher and public intellectual of bracingly liberal views who insisted that morality is the touchstone of constitutional interpretation, died Thursday in London. He was 81.
The cause was leukemia, said Richard Revesz, the dean of the New York University School of Law, who announced the death. Professor Dworkin had been a member of the school's faculty for many years and also taught at University College, London.
Professor Dworkin was "the primary legal philosopher of his generation," said Judge Guido Calabresi, a former dean of Yale Law School who now sits on the federal appeals court in New York. He was also one of the most closely read as a mainstay of The New York Review of Books, to which he contributed articles for decades.
Professor Dworkin's central argument started with the premise that the crucial phrases in the Constitution -- "the freedom of speech," "due process of law," "equal protection of the laws" -- were, as he put it, "drafted in exceedingly abstract moral language."
"These clauses," he continued, "must be understood in the way their language most naturally suggests: they refer to abstract moral principles and incorporate these by reference, as limits on the government's power."
It is not hard to hear echoes of Professor Dworkin's approach in the writings of Justice Anthony M. Kennedy, who often holds the crucial vote in morally charged debates before the United States Supreme Court and is quite likely to play a decisive role in two pending cases on same-sex marriage.
Professor Dworkin, in a 2005 interview, discussed Justice Kennedy's majority opinion in Lawrence v. Texas, a 2003 decision that struck down laws making gay sex a crime.
"The dominant voice you hear," Professor Dworkin said, "is about justice and injustice and what a decent society will tolerate and what it won't."
Thomas Nagel, a philosopher and Professor Dworkin's partner in a colloquium in legal, political and social philosophy offered for many years at New York University, said in a 2007 tribute that his friend's analytic power was amplified by the vigor and verve of his writing. Professor Dworkin, he said, could "explain difficult moral issues about law, politics and society in lucid terms to a general nonacademic audience -- without in any way watering them down or simplifying them."
His critics said Professor Dworkin's approach was a smoke screen. "Dworkin writes with great complexity but, in the end, always discovers that the moral philosophy appropriate to the Constitution produces the results that a liberal moral relativist prefers," Robert H. Bork, the onetime Supreme Court nominee, who died in December, wrote in 1997 in "The Tempting of America."
Judge Richard A. Posner, who sits on the federal appeals court in Chicago, wrote in a 2001 study of public intellectuals that Professor Dworkin's popular writings were slippery, partisan and predictable. "Dworkin's dominant bent as a public intellectual," Judge Posner wrote, "is to polemicize in favor of a standard menu of left-liberal policies."
Ronald Myles Dworkin was born in Providence, R.I., on Dec. 11, 1931. His parents divorced when he was young, and he said his memories of his father were hazy, though he believed his father had emigrated from Lithuania as a child. His mother, Madeline, raised three children on her own by teaching piano. He went to Harvard on a scholarship reserved for graduates of Providence's public schools. "There were rarely any takers," Professor Dworkin recalled.
After graduating from Harvard, he attended Oxford as a Rhodes scholar and obtained law degrees from both places. He spent much of his life with one foot in the United States and the other in Britain, living part of the year in each place.
Professor Dworkin was dashing, witty, well connected and open to earthly delight. "Dworkin is probably the least ascetic person I know, and one of the most worldly," Professor Nagel said in 2005.
After graduating from Harvard Law School, Mr. Dworkin served as a law clerk to Judge Learned Hand, a federal appeals court judge in New York and a towering figure in the law. In a letter to Justice Felix Frankfurter of the United States Supreme Court, Judge Hand called the young man "the law clerk to beat all law clerks," a compliment he undermined only slightly by calling him "Roland Dworkin."
Mr. Dworkin turned down an opportunity to serve as a clerk to Justice Frankfurter, a decision he later called "a very serious mistake." Instead he joined a prominent New York law firm, Sullivan & Cromwell, where he working as an associate from 1958 to 1962, specializing in international transactions.
In 1962, Professor Dworkin joined Yale Law School and began a glittering academic career. He returned to Oxford seven years later and soon put down roots in London.
In 1975, he turned down an offer from Harvard for a joint appointment in favor of New York University, whose law school is now among the best in the nation but had not yet achieved that status at the time. Enticing Professor Dworkin to join the faculty helped start the transformation. In later years he switched his primary British academic affiliation to University College, London, but the connection with N.Y.U. endured.
Professor Dworkin's first wife, the former Betsy Ross, died in 2000. He is survived by his wife, Irene Brendel Dworkin; his twin children, Anthony, a writer and expert on war crimes, and Jennifer Dworkin, a philosopher and filmmaker; and two grandchildren.
Professor Dworkin's academic work was in many ways a reaction to that of H. L. A. Hart, the British legal philosopher whose 1961 masterwork "The Concept of Law" set out his theory of positivism, which held that law is a system of rules similar in structure to those of games like chess. Legal reasoning, positivism says, is merely descriptive and need not take account of morality.
The two men first met when Professor Hart was by happenstance assigned to evaluate Mr. Dworkin's final examination at Oxford. The American student excited and scared Professor Hart, his biographer, Nicola Lacey, wrote in 2004, referring to Professor Hart by his first name.
"Herbert went on to express considerable anxiety about this student's views for the arguments of 'The Concept of Law,' " she wrote. Professor Dworkin's later work, she added, amounted to "a devastating critical onslaught" on Professor Hart's "overschematic account of adjudication."
Years later, when Professor Dworkin succeeded Professor Hart in the Oxford chair of jurisprudence, the older man gave an after-dinner speech quoting from the student paper, which he had saved.
Professor Dworkin's most influential book was "Law's Empire," on the nature and role of adjudication. It was among the most-cited books on law of the last century. He also wrote "Life's Dominion," on abortion, euthanasia and the questions they raise; "Sovereign Virtue," on equality; and three collections of essays, "Taking Rights Seriously," "A Matter of Principle" and "Freedom's Law."
In 2011, he published "Justice for Hedgehogs," an overview and summation. "I am trying," he said in 2005, as he was working on the book, "to bring together my work in law and my work in political philosophy and moral philosophy and the theory of interpretation and the kitchen sink."
That ability to synthesize and improvise served Professor Dworkin well, Professor Nagel said, recalling seeing his friend give a "beautifully constructed 50-minute lecture" at Stanford, having been introduced by the university's president.
"After it was over," Professor Nagel said, "the president got up again and explained that he had inadvertently picked up Dworkin's detailed lecture notes from the lectern after introducing him but discovered this only after Dworkin was launched."
This article originally appeared in The New York Times.