WASHINGTON – The nominee to be chief justice of the Supreme Court, Judge John Roberts Jr., sat quietly for the first three and half hours of his confirmation hearing yesterday, then stood, took an oath, and told members of the Senate Judiciary Committee that justices have a critical but limited role to play in service of the law and that, if confirmed, he will vigilantly defend the integrity and independence of the court.

“I have no agenda, but I do have a commitment,” Judge Roberts said in a seven-minute statement. “If I am confirmed, I will confront every case with an open mind. I will fully and fairly analyze the legal arguments that are presented. I will be open to the considered views of my colleagues on the bench. And I will decide every case based on the record, according to the rule of law, without fear or favor, to the best of my ability.”

The statement by the 50-year-old U.S. Circuit Court judge concluded a day of speeches in which nine Republican and eight Democratic senators expressed sharply divergent views on the Supreme Court’s role and that of nominees to it. Democrats argued for candor from the nominee. Republicans defended his right to remain silent on issues that could come before him in the future.

“Don’t take the bait,” Senator Cornyn, a Republican of Texas, advised the nominee. “Do exactly the same thing every nominee – Republican and Democrat alike – has done. Decline to answer any question that you feel would compromise your ability to do your job.”

The committee’s longest-serving member, Senator Kennedy of Massachusetts, cited Hurricane Katrina’s effects on poor residents of New Orleans as a reason for seeking to establish the nominee’s views on civil rights. Mr. Kennedy voted against Judge Roberts in committee following his nomination as a federal judge three years ago.

“I think America is about inclusion. We knocked down the walls of discrimination on race, on gender, on disability. Is this nominee an ally toward the continued march toward progress? Or is his view of the Constitution so constricted, so stingy, that he will move us in another direction?” Mr. Kennedy asked.

Describing the hearing as Judge Roberts’s “interview with the American people,” Mr. Kennedy joined his fellow Democrats in casting the event as a forum on the Supreme Court’s role in American society. He said strict readings of the U.S. Constitution threaten to impede “the great unfinished business of making America the land of opportunity for all” and said that Judge Roberts’s early writings raise questions about his commitment to that task.

Senator Biden, a Democrat of Delaware who chaired the last two Supreme Court hearings more than a decade ago, was more direct in critiquing so-called strict constructionists against those who, like himself, view the Constitution as a “living” document.

“Those elected officials on the far right, such as Mr. DeLay and others, have been unsuccessful at implementing their radical agenda in the elected branches – so they pour their energy and resources into trying to change the court’s view of the Constitution. And now they have a once-in-a-lifetime opportunity – the filling of two Supreme Court vacancies,” Mr. Biden said.

Senator Hatch initiated the counterattack for the Republicans, making an unsubtle jab at Senator Schumer of New York for publicly contradicting Republican claims that Justice Ruth Bader Ginsburg refused to answer questions put to her by the Judiciary Committee at her hearing in 1993. Like several of his Republican colleagues, Mr. Hatch, of Utah, urged members of the committee to treat Judge Roberts as a nominee for judicial, not political, office.

Judge Roberts’s age emerged as a central issue on the first day. The youngest nominee for chief justice in 204 years, Judge Roberts could potentially lead the court for decades. A number of senators cited this possibility as a reason to press Judge Roberts closely on his views. Senator Specter, the Pennsylvania Republican who chairs the committee, went so far as to suggest term limits for justices. Judge Roberts himself mentioned the possibility of term limits for justices while a young lawyer in the Reagan administration.

The intense scrutiny of Judge Roberts – senators have reviewed more than 70,000 pages of his writings – here underscored the sense, expressed by several senators, that the Supreme Court has become a crucial battleground in which some of America’s most divisive issues are, for better or worse, now played out.

Senator Coburn, a Republican of Oklahoma, drove the point home when he choked back tears in his opening remarks.

“When I think about the greatness, the possibilities of this country,” Mr. Coburn said, “my heart aches for less divisiveness, less polarization, less finger pointing, less bitterness, less mindless partisanship, which at times sounds hateful to the ear of Americans.”

Following statements by senators, Judge Roberts was introduced by two Republicans and Senator Bayh, a Democrat of Indiana who is eyeing a run for his party’s nomination for president in 2008. Mr. Bayh did not indicate how he plans to vote on the nominee: No Democratic senator has yet said how he or she will vote on the nomination.

The difficult part of the hearing begins today for Judge Roberts, who will face the first of what is likely be three days of questions from senators looking to learn more about his views on privacy rights, civil rights, and the overall role of the Supreme Court.