Judge Robert H. Bork forcefully expounded his conservative legal philosophy yesterday to the Senate Judiciary Committee during four hours of sometimes sharp but generally polite questioning over his fitness to serve on the Supreme Court.

Bork, pressed by committee liberals on whether he would attempt to overturn prior court rulings on civil rights and civil liberties, said "a judge must give great respect to precedent." Bork said his controversial writings on those issues and others did not mean that he would necessarily overturn those rulings.

The questioning at times focused on esoteric legal theories, but Bork's opponents and supporters on the committee carefully staked out their essential political strategies in a battle that could shape the future of the high court for years to come.

Bork's supporters want to emphasize that the federal appeals court judge and former Yale Law School professor appointed by President Reagan to fill the seat of retired justice Lewis F. Powell Jr. is not the right-wing activist liberals have accused him of being, but rather in the mainstream of accepted legal reasoning.

But Sen. Edward M. Kennedy (D-Mass.), Bork's most outspoken critic on the Judiciary Committee, said he "has harshly opposed -- and is publicly itching to overrule -- many of the great decisions of the Supreme Court that seek to fulfill the promise of justice for all Americans."

Bork, in his opening statement and in response to questioning from committee members, said his "philosophy of judging is neither liberal nor conservative," and that his view of judicial restraint meant that unelected judges should not "deprive the people of their liberty . . . to set their own social agenda."

He said his controversial criticism of numerous Supreme Court decisions was often not based on the outcomes of those cases but on the legal reasoning the court used in reaching its decisions.

For example, Bork said he opposed laws requiring sterilization of certain criminals and enforcing racially restrictive housing covenants even though he criticized Supreme Court decisions striking down those laws.

But Bork, under questioning by committee Chairman Joseph R. Biden Jr. (D-Del.) and Kennedy, did not back away from his controversial positions against Supreme Court rulings involving abortion, affirmative action or one-man, one vote or the right to privacy in general.

"I still think I was right," Bork said of his criticism of the Supreme Court's "one-man, one-vote" ruling that forced legislative bodies to redraw their districts based on population.

Asked about the court's landmark 1973 ruling legalizing abortion, Bork said the decision "contains almost no legal reasoning." But he said he did not know how he would rule if an abortion case came before him.

He said the only position he has taken was in criticizing the court's legal reasoning in concluding there is a constitutional right to abortion.

This and other exchanges during the hearing were generally polite and often couched in technical legal terms. But Bork's opponents were cheered that Bork, while an affable witness, stuck to some of his more controversial views.

"To the extent that the White House thought Bork would portray himself as a flexible moderate, those hopes were dashed," said a senior political aide to Biden, a candidate for the 1988 Democratic presidential nomination. "Bork betrayed himself as Bork today."

Committee Republicans, however, heaped praise on Bork, who sat impassively through the lengthy opening statements of committee members that took up the morning session and spilled into the afternoon and answered questions in a relaxed, conversational tone.

"I don't see how anyone watching this can doubt that you are an eminent scholar, with a great mind, in the judicial mainstream of the country," Sen. Orrin G. Hatch (R-Utah) told Bork.

Biden went out of his way to assure Bork that the hearings would be fair but did not attempt to conceal his announced opposition to the nomination. Following Bork's opening statement, Biden, the first questioner, attempted to pin him down on the issue of privacy.

Bork has repeatedly criticized a 1965 ruling, Griswold v. Connecticut, in which the Supreme Court struck down a state law prohibiting married couples from using contraceptives. The court said the law violated a constitutional right to privacy.

Bork, who has described the Connecticut law as "nutty," said there might be some legal grounds on which to strike down the law but that there was no general right to privacy contained in the Constitution.

Biden countered by citing a 1971 article and a 1982 speech in Washington by Bork in which he said the result in the Griswold case could not be justified under any legal reasoning.

Under questioning by Kennedy, Bork acknowledged, as he had in his 1973 confirmation hearing for the post of solicitor general at the Justice Department, that he was wrong in opposing passage of the public accommodations section of the 1964 civil rights law. But he defended his criticism of a Supreme Court decision striking down a Virginia poll tax and his stand on the "one-man, one-vote" case.

Bork also defended his assertion that the court had improperly extended the equal-protection clause of the 14th Amendment to cover sex-discrimination claims.

"Your views would take us back to the days when women were second-class citizens," Kennedy said.

Asked about his opposition to the Equal Rights Amendment, Bork said:

"I never said anything about the ERA except it seemed to me odd to put all the decisions dealing with women in the hands of judges. I didn't campaign against it; I just dropped a footnote some place."

In their questioning, Bork's supporters gave the Supreme Court nominee a chance to expound his philosophy and respond to questions that have been raised about his record.

In response to Sen. Strom Thurmond (R-S.C.), Bork dismissed as "preposterous" an allegation by a federal judge charging that while on an appeals court panel he had improperly attempted to substitute his own views for the reasoning agreed on by the two other judges. The charge was made in a letter to the Judiciary Committee from U.S. District Court Judge James F. Gordon of Kentucky.

"There's nothing to the charge," Bork said. "The memories of the people involved, the documentation, and the practicalities of the circumstances indicate it's just -- I don't know what it is, but it's certainly a misunderstanding."

As the Judicary Committee hearings began, The Cleveland Plain Dealer reported that a confidential Federal Bureau of Investigation background investigation had discovered two incidents, on Dec. 21 and Dec. 23, 1983, when Bork was rushed to Sibley Memorial Hospital in Northwest Washington after falling down.

The paper said that during the second visit to the hospital's emergency room a test showed the level of alcohol in Bork's blood was .09, considered enough to impair driving ability. Bork was taken to the hospital by ambulance, the report said.

The Plain Dealer said Bork's account of the incidents was that on Dec. 21 he slipped on an icy walkway and broke his arm. Two days later at a Christmas party at his house, with his arm in a sling, Bork said he tripped on a stairway, the paper said.

Democratic sources on the Judiciary Committee said Biden "does not feel there is substance" to the reports of the incidents "and does not intend to pursue it."

In their opening statements before Bork's testimony, the committee's eight Democrats and six Republicans laid out the cases for and against Bork that have been building over the summer. Every committee Republican except Sen. Arlen Specter (Pa.) strongly defended Bork and attacked what Hatch called "the impending ideological inquisition" the judge faces.

Sens. Specter, Dennis DeConcini (D-Ariz.) and Howell T. Heflin (D-Ala.) are considered the swing votes who will decide whether the committee endorses the nomination. Each voiced concern about Bork's approach to several issues centering on questions of whether he would deal with court cases with an "open mind."

"I must be satisfied that in the guise of what you represent and what Attorney General {Edwin} Meese calls 'judicial restraint,' you are not a conservative judicial activist bent on imposing his own political philosophy on the court and the nation," DeConcini said.

Heflin said Bork will improve his chances of confirmation if he can show that he "will balance society's need for law and order with individual rights and personal freedoms" and that "you do not have a proclivity for activism.

"However," Heflin continued, "if the evidence shows that you are intelligent but an ideologue, a zealot, that you are principled but prejudiced, that you are competent but closed-minded, then there is considerable doubt as to whether you will be confirmed by the Senate."

Bork was accompanied to the hearings by his wife and three children, who sat behind him as he testified, and by a group of Republican supporters headed by former president Gerald R. Ford and Senate Minority Leader Robert J. Dole (R-Kan.).

Formally introducing Bork to the committee, Ford said he "may well be the most qualified nominee to the Supreme Court in more than half a century."