John G. Roberts Jr. assured senators considering his Supreme Court nomination today that he would not be "an ideologue" if confirmed as chief justice, and he defended a legal career that he said may lead some critics to call him a "hired gun."

Appearing for a fourth and final day before the Senate Judiciary Committee, Roberts said his arguments as an attorney on both sides of some key issues, including affirmative action, show his deep respect for the rule of law, a value that he said would guide him on the high court.

After answering questions for about two hours this morning, Roberts went into a closed session with the committee to address an FBI report and any other investigative matters. The committee chairman, Sen. Arlen Specter (R-Pa.), emerged about half an hour later to say there were "no disqualifying factors" in Roberts's background. Sen. Patrick Leahy (D-Vt.), the top Democrat on the committee, concurred, calling the closed session a "housekeeping chore."

A committee of the American Bar Association, whose representatives testified after the closed session, unanimously found Roberts "well qualified" to be chief justice. Steve Tober, the chairman of the committee, said it had interviewed more than 80 judges, lawyers and community members, reviewed previous reporting and interviewed Roberts personally.

"He has the admiration and respect of his colleagues on and off the bench," Tober said. "And he is, as we have found, the very definition of collegial."

In an afternoon session, civil rights advocates debated Roberts's record, arguing for and against the nominee. Rep. John Lewis (D-Ga.) told the committee that Roberts's memos as a lawyer for the Reagan administration showed him to be "hostile to civil rights and to the Voting Rights Act." Peter Kirsanow, a member of the U.S. Commission on Civil Rights, said Roberts was "exemplary" in his approach to civil rights and has "a deep appreciation for the civil rights cause."

Roberts, nominated by President Bush to replace the late Chief Justice William H. Rehnquist, faced questioning this morning mainly from Democratic senators, some of whom said they were still wrestling with the question of whether to vote to confirm him.

"I don't really know what I'm going to do," said Sen. Dianne Feinstein (D-Calif.). She previously had said that she would not vote for a nominee whom she knew would act to overturn Roe v. Wade, the landmark 1973 Supreme Court decision legalizing abortion.

Sen Charles E. Schumer (D-N.Y.) said he has woken up in the middle of the night thinking about which way to vote on the confirmation. Given that Roberts would become chief justice at a relatively young age and make decisions that could affect all Americans for generations, Schumer said, referring to a Democratic colleague's statement, "This isn't just rolling the dice. It's betting the whole house."

Schumer listed pros and cons, saying that one major factor in favor of Roberts is his "brilliance" and "amazing knowledge of the law." Said Schumer, "You may very well possess the most powerful intellect of any person to come before the Senate for this position." He also cited the nominee's love of the law and his professed judicial philosophy of "modesty and stability."

But Schumer said he had questions about "the fullness of your heart." He mentioned Roberts's refusal to concede that his reference in a memo two decades ago to "illegal amigos," a term that Hispanic groups have criticized, was "unfortunate," or that other past positions were misguided. Schumer also complained that Roberts had refused to answer many questions, adding that transcripts he read later of Roberts's testimony before the panel showed that "there was less than met the ear."

Schumer asked whether Roberts would be "a truly modest judge," a "very conservative judge" like Rehnquist who would nevertheless "not use the bench to remake society," or a judge who would use his talents "to turn back a near-century of progress and create the majority that Justices [Antonin] Scalia and [Clarence] Thomas could not achieve."

Roberts replied that in reaching a judgment on that question, the senators should examine "what kind of a judge I've been" and look at his 50 opinions on the federal bench.

"I don't think you can read those opinions and say that these are the opinions of an ideologue," Roberts told Schumer. "You may think they're not enough. You may think you need more of a sample. That's your judgment. But I think if you've looked at what I've done since I took the judicial oath, that should convince you that I'm not an ideologue. And you and I agree that that's not the sort of person we want on the Supreme Court."

Sen. Lindsey O. Graham (R-S.C.), a strong supporter of Roberts, said later, "Nobody can question your intellect. . . . So we're down to the heart."

He cautioned, "Well, there are all kind of hearts. There are bleeding hearts and there are hard hearts. . . . And I want this committee to understand that if we go down this road of putting people's hearts in play, and the only way you can have a good heart is adopt my value system, we're doing a great disservice to the judiciary."

Feinstein questioned Roberts about a memo he wrote that she said suggested opposition to a Supreme Court ruling in Plyler v. Doe that said states must educate children who are illegal immigrants. Roberts said, "I have no quarrel with the court's decision. . . . I certainly believe every child should be educated."

"Regardless of immigration status?" Feinstein asked.

"My own view is that if you have a child, he or she should be educated. We'll worry about status later. . . . It's a separate issue as a legal question, as you know."

Roberts disputed a study by a Duke University Law School professor, who examined nine cases he had heard as a judge on the U.S. Court of Appeals for the District of Columbia Circuit and concluded that, as Feinstein put it, "you ruled in favor of a corporation each time." She asked him to respond to the professor's conclusion that "you're going to be a fairly reliable vote against workers' rights across the board."

Said Roberts, "I think the conclusion is wrong. I would suggest that any examination of nine cases is too small of a statistical sample to draw any conclusions of that sort." He said he has "ruled against corporations on a regular basis on the D.C. Circuit," and cited another study showing that he tended to do so "more than the average judge." He also said he has ruled for and against federal regulatory agencies in different cases.

Roberts was pressed by Sen. Richard J. Durbin (D-Ill.) about his "core values" and whether he would ever "draw the line" in his legal advocacy or would "play for any team that asks you to play." Durbin asked, "As a lawyer, do you have standards and values as to the causes and beliefs that are so important to you where you would draw a line?"

Roberts said people become lawyers for different reasons, such as protecting the environment, advancing civil rights or promoting other causes.

"I became a lawyer -- or at least developed as a lawyer -- because I believe in the rule of law," Roberts said. "Now, that means that that's at issue and play regardless of what the cause is." He said he has worked on cases promoting environmental causes and argued on both sides of affirmative action and antitrust issues.

"In each case, I appreciated that what I was doing as a lawyer, particularly as a lawyer before the Supreme Court, was promoting the rule of law in our adversary system. . . . I appreciate that some may say, 'Well, that sounds like you're a hired gun. . . . You're going to take the side of whomever comes in the door first.' I think that's a disparaging way to capture what is, in fact, an ennobling truth about the legal system: that lawyers serve the rule of law, above and beyond representing particular clients."