UNIVERSITY PARK, Texas — President Barack Obama joined all of his living predecessors Thursday to pay tribute to George W. Bush as the arguments of the past decade gave way, at least for a day, to a more generous appraisal of a leader who responded to great challenges with determination and grit.

The current and former presidents gathered to dedicate the George W. Bush Presidential Library and Museum here on the campus of Southern Methodist University. Joining them was a collection of current and former foreign leaders and lawmakers as well as hundreds of former Bush administration officials and thousands of his admirers.

Obama praised Bush for his resolve after the attacks of Sept. 11, 2001, his compassion in fighting AIDS in Africa and his commitment to overhauling the immigration system. Treading lightly over their disagreements over Iraq and other issues, the president said his predecessor had fought for what he thought was best for his country.

“We know President Bush the man,” Obama told the crowd in front of the brick-and-limestone center on a bright, sunny Texas day. “To know the man is to like the man. Because he’s comfortable in his own skin. He knows who he is. He doesn’t put on any pretenses. He takes his job seriously but he doesn’t take himself too seriously. He is a good man.”

It was an emotional moment for Bush, coming four years after leaving office with historic low poll numbers. Bathed in the admiration of his former team and his presidential peers, he recalled the goals that guided his time in office and choked up as he finished his speech. Sitting down to applause, he smiled and wiped tears from his eyes.

“In democracy, the purpose of public office is not to fulfill personal ambition,” he said. “Elected officials must serve a cause greater than themselves. The political winds blow left and right, polls rise and fall, supporters come and go. But in the end leaders are defined by the convictions that they hold.”

Bush, 66, acknowledged the controversies of his time, noting that freedom means the freedom to disagree. “It’s fair to say I created plenty of opportunities to exercise that right,” he said with a smile.

But he added that visitors to his library will see how he saw it. “They’re going to find out that we stayed true to our convictions,” he said, “that we expanded freedom at home by raising standards in schools and lowering taxes for everybody, that we liberated nations from dictatorship and freed people from AIDS. And that when freedom came under attack, we made the tough decisions required to keep the American people safe.”

Laura Bush opened the ceremony by honoring her husband as a caring man who comforted a nation during times of terrorism and war as president and has continued to help the afflicted by rehabilitating a health clinic in Africa as a former president. “I remember how steadfast and steady he was for eight years,” she said, adding, “My George is a man who when someone needs a hand offers them their arms.”

In addition to Obama, former Presidents Jimmy Carter, Bill Clinton and George H.W. Bush spoke at the program.

The event was a public re-emergence of sorts for the elder Bush, 88, who spent weeks in a hospital last winter and at one point appeared close to death. Now in a wheelchair because of a form of Parkinson’s disease in his legs, Bush, the 41st president, has recovered considerably and remains lively and engaged, according to people who have seen him lately.

Bush said only a few words thanking the crowd and those who had made the library. “It’s very special for Barbara and me,” he said, wrapping up by saying, “God bless America, and thank you very much.”

Clinton, who has become so close to the Bushes that he is often described as a virtual member of the family, offered warm praise for Bush as a president and quasi-brother, mentioning as Obama did, the AIDS program and immigration fight.