Ronald Dworkin, a legal philosopher and public intellectual of bracingly liberal views who insisted that morality is the touchstone of constitutional interpretation, died on 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.”