Justice Potter Stewart sometimes wrote prose that seemed almost profane in the land of legalese but was sacred in the land of clarity.

In 1964, for example, five years after coming to the Supreme Court he is now leaving, he admitted in a separate opinion that he might never succeed in defining the reach of "hard-core pornography."

"But I know it when I see it, and the motion picture involved in this case is not that," he wrote.

In 1972, he wrote why death penalties, when imposed with no rhyme or reason, are in their capriciousness violations of the English Amendment, which bars cruel and unusual punishment:

"These death sentences are cruel and unusual in the same way that being struck by lightning is cruel and unusual."

In 1978, the court faced an obviously sensitive issue raised by an Indiana state judge who approved the sterilization of a 15-year-old girl without her knowledge or consent.

By a vote of 5 to 3, the justices voted that their distant brother could not be sued for damages because he was clothed in absolute judicial immunity.

Under the leadership of Chief Justice Warren E. Burger, dissents, like children, were usually supposed to be seen, not heard. Stewart chose to be heard, reading his dissent aloud with electrifying effect:

"A judge is not free, like a loose cannon, to inflict indiscriminate damage whenever he acts in his judicial capacity."

There is less dispute about Stewart's pithy eloquence than there is about his record of judicial achievement.

First, a critic: Arthur S. Miller, a retired constitutional law professor at George Washington University who is completing a book on the court. "Stewart has been a major disappointment. He has never lived up to his potential. He never had a discernible, consistent philosophy, except on freedom of the press matters and on protection of the existing economic system."

Next, praise from Robert H. Bork, Alexander M. Bickel Professor of Public Law at Yale Law School, Stewart's alma mater: "He had a very distinguished career."

Now, for a mixed but favorable appraisal by Harvard constitutional scholar Laurence H. Tribe:

Stewart has "probably not" fulfilled his potential. But he was "often underestimated and did make a distinguished contribution."

"He is a jurist of greater gifts than the opinions he has had an opportunity to write tend to demonstrate," Tribe said.

"His most consistent philisophy has been skpeticism about the virtues of apparently consistent philosophies," he said. "He has believed it was the essence of judging to decide, under the Constitution, without the potential distortion of a philosophical ax to grind."

Some judges and lawyers question the need for oral agruments before the court, contending that they are mostly a time-wasting overlay on printed briefs. But many who have heard Stewart at the top of his form -- Tribe among them -- disagree. Stewart, Tribe, said, used oral argument effectively to fulfill its purpose, "as a way of sharpening issues and focusing his own understanding."

In 1974, Stewart, who in the mid-1930s was a cub reporter in Cincinnati, returned to Yale Law School to give a memorable talk about what he saw as the special protection afforded the press by the First Amendment.

"The press is free to do battle against secrecy and deception in government," he said. "But the press cannot expect from the Constitution any guarantee that it will succeed."

This speech helped to win Stewart a reputation for being what Bruce Fein, a specialist on the court for the American Enterprise Institute, calls a "staunch defender" of the first Amendment.

In 1978, confirming that he and Chief Justice Burger are poles apart on the issue, Stewart said he would admit television cameras to oral arguments. The issue is nearly certain to be one that will be raised with the person nominated to succeed him.

In recent years, Fein believes, Stewart became increasingly disenchanted with judicial activism -- with courtled rather than legislated changes in society -- even when Stewart may have personally regarded a particular legislative policy as misguided.

One of Fein's examples involved capital punishment. Stewart, in his 1972 opinion, said the Constitution would not let a state impose it in a "freakish" way. But in 1976, Fein pointed out, Stewart made clear that he was unwilling to second-guess legislatures when he wrote that the death penalty, in and of itself, is not unconstitutional cruel and unusual punishment.

Stewart's mentor when he came to the court was John Marshall Harlan, a justice revered by many as an exemplar of thoughtful, principled conservatism. In "The Brethren," the 1980 book on the court's inner workings, authors Bob Woodward and Scott Armstrong said that Harlan, who died in 1971, imbued Stewart with the belief that the court should interpret the law with an intellectual consistency that would be a beacon of guidance to the lower courts, rather than deciding cases on a pragmatic, ad hoc basis.

Stweart, himself a former judge of the 6th U.S. Circuit Court of Appeals, "feared that the lower courts would lose faith in the Supreme Court if it came out with some abstract announcement," the book said.

The author said that more than any of the eight other justices, Stewart was a coalition builder, even if this was sometimes hidden from the public by opinions that other wrote in speaking for the court.

According to Woodward and Armstrong, it was in such contexts that the optimism Stewart had at the outset of the Burger era, in 1969, began to erode. An early school desegregation case provided Stewart with "a demonstration of the new chief's inability to lead them through a crisis." Later, the court had to deal with the explosive case in which the Nixon White House refused to supply crucial tape recordings to the Watergate special prosecutor.

Burger's preliminary actions dismayed Stewart, the authors said. "On ocean liners," they said he told his clerks, "they used to have two captains. One for show, to take the women to dinner. The other to pilot the ship safely. All we need now is a real captian."

Two years ago, in a talk to the Cincinnati Bar Association, Stewart said, "A justice does not forget how much may depend on his decision. He knows that it may affect the course of important social, economic and political currents."

That same course will be affected, no one possibly could know how, by the decision he disclosed yesterday. "I leave with the hope that the Supreme Court will be in good and wise hands," he wrote to the president who will nominate his successor.