The 83-year-old pope presided over an anniversary Mass in St. Peter's Square that started at 6 p.m. (noon EDT) — about the same time that white smoke from a Vatican chimney alerted the world a quarter-century ago that a Polish cardinal named Karol Wojtyla had been elected the first non-Italian pontiff in 455 years.
The crowd broke into applause when a weary-looking John Paul was wheeled out to the altar in his throne-like chair, dressed in golden vestments and a bejeweled miter, or bishop's hat, while a choir sang hymns.
The 83-year-old pope, who suffers from Parkinson's disease, read only portions of his prepared remarks, including a prayer, and appeared pained at times. He spoke in a strong voice during his homily, but began slurring his words later in the two-hour service.
"I renew, in the hands of Mary, beloved Mother, the gift of myself, of the present and the future: everything will be done according to Your will. Supreme Pastor, stay among us so that we can proceed with You securely to the house of the Father."
And in a portion read by an aide, John Paul said, "Help the pope and all those who want to serve Christ."
In an opening greeting, Cardinal Joseph Ratzinger, a close papal aide, praised the pope for his tireless work over 25 years.
"You turned to young and old, rich and poor, powerful and humble, and always showed, according to the example of Jesus Christ, a particular love for the poor and the defenseless," Ratzinger said.
CBS News Correspondent Charles D'Agata reports thousands of pilgrims of all nationalities surrounded St. Peter's Square for the celebration mass hours before it was to start, with more of the feeling of an international carnival than a religious gathering.
"There are pilgrims here from all over the world and they are just full of faith and full of joy and celebration," agreed CBS News Early Show co-anchor Harry Smith.
That includes lots of people from Poland, at the Vatican in full force to honor their hometown boy, and representatives from the 301 Roman parishes John Paul has visited. Millions more were expected to watch on television.
Residents of Pope John Paul II's hometown of Wadowice, Poland, gathered in cold, wet weather Thursday for an outdoor Mass in the central square that bears his name, praying for his health as they celebrated a quarter-century of his papacy.
An altar bedecked with white and yellow flowers and Polish flags was set up in front of the St. Mary's Church, the centerpiece of the John Paul Square at the heart of Wadowice, a town of 20,000.
In Krakow, the Wawel Cathedral's historic Zygmunt bell chimed at 6:18 p.m. — the time that John Paul's election was announced 25 years ago. Special anniversary services also were held across the country.
The atmosphere in Rome was festive, but also bittersweet, because the pope, who suffers from Parkinson's disease, is so clearly ailing.
"He's frail, of course," Washington D.C. Archbishop Theodore McCarrick, who spoke with a pope a week ago, told Smith. "We know he's not this giant that strolled across the pages of history 25 years ago that we all were so fascinated by, but I think his mind is still fine."
Nevertheless, John Paul has continued to defy skeptics by insisting on keeping up with his taxing schedule though he is unable to walk or even stand. He also continues to hold public audiences despite his increasing difficulty speaking, and he has made clear he has no plans to step down.
On church doctrine, John Paul has toed a conservative line: abortion, contraception and euthanasia are all banned in the church under John Paul. He ruled out letting priests marry or allowing women to be ordained, and recently endorsed a worldwide campaign to keep same-sex unions from receiving legal recognition.
Such hard-line positions alienated some Catholics and sparked criticism that the Vatican was out of touch with 21st century society. In particular, the church's opposition to condoms has been blamed by some for hurting the fight against AIDS.
"We're living in a world that doesn't accept absolutes...and this man is saying love has to be absolute. You'll have to put your life on the line. You have to decide. You can't bargain with the Lord. You have to be 100 percent," McCarrick said on The Early Show.
A recent poll found that 90 percent of American Catholics approved of the way John Paul had set a moral example, argued for human rights and encouraged democracy. But two-thirds of respondents in the ABC-Washington Post poll said they opposed the church's ban on contraception and married priests, saying the church was out of step with their own lives.
John Paul is the most-traveled pope ever, visiting 129 different countries in 102 foreign trips. He made more saints than any of his predecessors over the past 500 years combined — a total of 476 — part of his aim to give his sometimes flagging flock more role models.
John Paul also ushered the Vatican into the media age, becoming something of a superstar and drawing cheering crowds wherever he went, particularly among the young. Over the course of his pontificate, more than 16.7 million people by Vatican statistics attended his weekly Wednesday general audiences alone.
"He is truly the global pope," said Cardinal Christoph Schoenborn, the archbishop of Vienna, Austria and a man mentioned as a possible successor to John Paul.