VATICAN CITY -- Pope Benedict XVI, outlining an agenda for his pontificate less than 24 hours after it began, pledged his openness yesterday to communicate with young people and with adherents of other faiths and praised the late John Paul II for leaving behind a Catholic Church ''that is more courageous, freer, younger."
Speaking in Latin during a Mass at the Sistine Chapel, before an image of Jesus pointing menacingly toward the damned in Michelangelo's fresco ''The Last Judgment," the new pope vowed to continue the work of his predecessor. But he also appeared to respond to some of his critics by declaring himself open to advice from bishops and intent on improving relations with non-Catholic Christians.
In his first extended public remarks since he was named pope Tuesday evening, the 78-year-old Benedict said his election surprised ''every pre-vision I had" and that he felt ''a sense of inadequacy and human turmoil for the responsibility entrusted to me."
He also said that ''the weight of the responsibility that now lies on my poor shoulders is enormous," but that ''the divine power on which I can count is surely immeasurable."
Benedict said he found comfort by thinking about his predecessor and friend, John Paul, who died April 2 after a 26-year pontificate.
''It seems I can feel his strong hand squeezing mine; I seem to see his smiling eyes and listen to his words, addressed to me especially at this moment, 'Do not be afraid!' " Benedict said.
Benedict's openness to dialogue, his emphasis on ecumenism, his admission of feelings of inadequacy, and his warm overture to young people all run counter to his public image. In the past, he has been seen as a brilliant but stern and even chastising figure, for example, when he wrote in 2000 that ''the followers of other religions . . . are in a gravely deficient situation" and in 1986 that homosexuality is an ''intrinsic moral evil."
The new pope, until his election Cardinal Joseph Ratzinger, is a German theologian who for more than two decades had been John Paul II's chief enforcer of doctrinal orthodoxy as prefect of the Congregation for the Doctrine of the Faith. He made his remarks yesterday at the close of a Mass for cardinals that was broadcast by Vatican television.
The Vatican also released footage of Benedict yesterday entering the papal apartment in the apostolic palace, which has been vacant since John Paul's death. Benedict was shown walking through the halls of the palace, smiling and waving at the staff, sitting at a desk in the apartment, and signing his new name on a piece of paper.
Later, he briefly mingled with a cheering crowd outside his longtime apartment in Rome, where he will continue to live until a renovation of the papal apartment is complete. Accompanied by bodyguards, he stopped to bless several children, then ducked into a black Mercedes limousine, Reuters reported.
But the main event of the day was his message. Vested in golden robes and speaking while seated on a white throne, Benedict said that forging unity between Christians of different denominations and churches is his ''primary commitment." He also pledged to listen to the ''expectations" of young people, an emphasis of John Paul II, and to attend the next World Youth Day, in August in Cologne, Germany.
He said he would pursue reforms set into motion by the Second Vatican Council, although scholars said that there is considerable division between conservatives such as Benedict and liberals over what changes were intended by that gathering from 1962-65.
His remarks on ecumenism, or relations between Christians -- as well as on interfaith relations, those between Christians and non-Christians -- were particularly striking. Some advocates of such dialogue have criticized Benedict because of several documents he wrote, including, in 2000, ''Dominus Iesus." in which he declared that ''the church of Christ, despite the divisions which exist among Christians, continues to exist fully only in the Catholic Church."
''His interpretations of the ecumenical vision of Vatican II have been narrow and constrained, and he has persisted in describing the ecclesial status of non-Catholic churches in ways that have been insensitive and demeaning," said a statement released by the Rev. John H. Thomas, general minister and president of the United Church of Christ.
But in his remarks yesterday, Benedict declared himself ''fully determined to cultivate any initiative that may seem appropriate to promote contact and agreement with representatives from the various churches and ecclesial communities."
''Benedict XVI clearly wants to dispel the myth that he is opposed to ecumenism," said Mark Brumley, president of Ignatius Press, which is the US publisher of Benedict's many works, including books on theology and a memoir.
Benedict's comments drew praise from the Rev. Diane C. Kessler, executive director of the Massachusetts Council of Churches, who is a longtime leader in ecumenical relations. Kessler called the pope's remarks ''very encouraging."
''He reflected on John Paul II smiling at him and saying from beyond the grave, 'Do not be afraid,' and I thought, as I was reading his remarks, that nor should we, his ecumenical colleagues, be afraid," Kessler said by telephone.
Benedict also spoke of the importance of evangelization and of caring for the poor, saying Christian faith requires ''the ardor of charity towards all, especially towards the poor and the smallest."
Cardinal Theodore E. McCarrick of Washington, D.C., described Benedict's remarks as akin to a State of the Union address for the church, and scholars said the message offered early clues about Benedict's papacy.
''It's not going to be a brief and transitional papacy, in the sense of a holding action, but it's going to be a very consequential picking up of the baton passed on by John Paul II and a very determined effort to change the world through renewal of the church," said the Rev. Richard John Neuhaus, editor of First Things, a New York-based journal of religion and culture. ''He's a very determined person with very definite views, and I think we'll see a lot of things very quickly."
Another scholar in Rome said the tone of Benedict's remarks was warm, in keeping with his homily at John Paul II's funeral.
''It confirms that he's going to be a kind shepherd, respectful of everyone and ready to dialogue," said the Rev. Robert A. Gahl Jr., a professor of ethics at the Pontifical University of the Holy Cross. ''And, as a priest, I was very struck by his words directed towards priests, because many of us, following the difficulties of the sexual abuse crisis and the death of John Paul II, felt ourselves as orphans."
Benedict plans to hold a press conference Saturday, and on Sunday his pontificate will be formally inaugurated with a Mass in St. Peter's Square.
Stephen Heuser of the Globe staff contributed to this report. Michael Paulson can be reached at firstname.lastname@example.org.