SOUTH BEND, Ind. — Amid a scattering of angry protests over his support for abortion rights, President Obama addressed the issue head-on yesterday at the University of Notre Dame, calling for "open hearts, open minds, fair-minded words" in the pursuit of "common ground."

Since becoming president, and before that for nearly two years on the campaign trail, Obama has sought to skirt the emotional anger that surrounds the debate over abortion. But his decision to speak to graduating Notre Dame students made that approach impossible yesterday.

The invitation from one of America's best-known Catholic universities ignited a firestorm of discussion over whether an institution that adheres to the Roman Catholic Church's condemnation of abortion should award an honorary law degree to a president who is committed to safeguarding abortion rights.

Obama appeared energized by the controversy over his appearance, and he addressed the debate over abortion with relish. He pleaded for courtesy in the dialogue even as he acknowledged that "at some level, the views of the two camps are irreconcilable."

"Is it possible for us to join hands in common effort?" he said. "As citizens of a vibrant and varied democracy, how do we engage in vigorous debate? How does each of us remain firm in our principles, and fight for what we consider right, without demonizing those with just as strongly held convictions on the other side?"

LOUD OVATIONS

The vast majority of the 12,000 in attendance at the Joyce Center basketball arena gave the president several loud, sustained ovations, and the crowd rallied to his defense when people attempted to interrupt him at the start. One protester yelled "Abortion is murder!" "Baby killer!" and "You have blood on your hands." Another shouted, "Stop killing our children." The crowd responded with boos and then chants of "Yes, we can" and "We are N.D."

A handful of graduates engaged in a silent protest, having taped a yellow cross and yellow images of baby feet to the top of their mortarboards.

Meanwhile, hundreds of anti-abortion protesters gathered yesterday outside the front gate of the university, beyond the view of the presidential motorcade; police arrested more than three dozen for trespassing, including Norma McCorvey, the woman at the center of the landmark Supreme Court abortion case Roe v. Wade, who is now an anti-abortion activist. Billboards on the nearby Indiana Toll Road read: "Notre Dame: Obama is pro abortion choice. How dare you honor him."

Obama did not engage in the debate over when life begins, nor did he attempt to justify his beliefs about abortion or embryonic stem cell research, positions that some said should have disqualified him from Notre Dame's honorary degree. Instead, the president took aim at the loud and angry rhetoric that he said too often dominates the discussion.

The failure of both sides to use "fair-minded words," he said, overly inflames an important debate. As an example, he described his own 2004 campaign Web site, which at one point referred to "right-wing ideologues who want to take away a woman's right to choose."

It was not until a doctor e-mailed him about the phrase that Obama ordered it taken down, he said.

"I didn't change my underlying position, but I did tell my staff to change the words on my Web site," he told the crowd. "And I said a prayer that night that I might extend the same presumption of good faith to others that the doctor had extended to me. Because when we do that ... that's when we discover at least the possibility of common ground."

Obama's call was echoed by the university's president, the Rev. John Jenkins, who chided those who had spoken angrily about Obama's visit. He urged the Notre Dame community to appeal to both "faith and reason."

The university seeks "to foster dialogue with all people of good will, regardless of faith, background or perspective," Jenkins said. He praised Obama for accepting the invitation to speak despite the controversy.

"President Obama has come to Notre Dame, though he knows full well that we are fully supportive of the church's teaching on the sanctity of life," Jenkins said. "Others might have avoided this venue for that reason."

BISHOPS CRITICAL

More than 70 Catholic bishops criticized Jenkins for inviting Obama, and more than 360,000 people signed a petition calling for the invitation to be rescinded.

Obama's upcoming nomination of a new Supreme Court justice is likely to spark an even more heated abortion debate. Anti-abortion activists have vowed to loudly oppose any nominee for the court who supports abortion rights.

It was the second time in a week that he had used a commencement address to recast a discussion about him into a broader context.

At Arizona State University's graduation Wednesday, Obama talked directly about the school's decision to deny him an honorary degree on the basis that he lacks the accomplishments to justify the accolade. "His body of work is yet to come," university officials had said.

"Your own body of work is also yet to come," he told 60,000 people at the stadium. "Building a body of work is all about ... the daily labor, the many individual acts, the choices large and small that add up over time, over a lifetime, to a lasting legacy. That's what you want on your tombstone. It's about not being satisfied with the latest achievement, latest gold star — because one thing I know about a body of work is that it's never finished."

Obama did not shy away from the abortion controversy yesterday. He stressed the need for cooperation and good will even among those who disagree about the most morally weighted issues.