"To protect Jesus with Mary, to protect the whole of creation, to protect each person, especially the poorest, to protect ourselves: This is a service that the Bishop of Rome is called to carry out," Francis said during his homily, "yet one to which all of us are called, so that the star of hope will shine brightly. Let us protect with love all that God has given us."
In Joseph, a carpenter whose life is celebrated Tuesday, "we learn how to respond to God's call, readily and willingly, but we also see the core of the Christian vocation, which is Christ," Francis said. "Let us protect Christ in our lives, so that we can protect others, so that we can protect creation!"
Thousands of people assembled in St. Peter's square to watch as Francis began the ceremonial mass inside the basilica to install him as the 266th pope of the Catholic church. The pope arrived standing in the rear of a white convertible rather than a covered version of the traditional "popemobile" that is protected by bulletproof glass, The New York Times reported.
As he passed through the piazza, the pope, stopped occasionally to kiss a baby or other onlookers, even giving a thumb's up sign, which drew laughter, the Times said.
Dignitaries from around the world attended the two-hour ceremony, including a delegation from Argentina, Francis' native country. The Vatican said Monday representatives of 132 countries and international organizations were expected to attend the installation mass.
As the mass began, Francis received two symbolic emblems of his office: The fisherman's ring, which recalls how St. Peter, the first pope, fished for food and later for souls, and the pallium, a white woolen vestment symbolizing the role of the pope as a good shepherd for the 1.2 billion Catholics worldwide.
During his sermon, Francis also asked those in "positions of responsibility in economic, political and social life, and all men and women of good will: Let us be 'protectors' of creation, protectors of God's plan inscribed in nature, protectors of one another and of the environment."
Recognizing a pope has power, Francis said authentic power is service, and a pontiff must be dedicated to a life service.
"He must be inspired by the lowly, concrete and faithful service which marked St. Joseph and, like him, he must open his arms to protect all of God's people and embrace with tender affection the whole of humanity, especially the poorest, the weakest, the least important," Francis said. "Only those who serve with love are able to protect!"
Before Francis' inaugural mass, the pontiff indicated heads may roll at the Vatican's fractious governing bureaucracy, the Curia, Cardinal Peter Turkson of Ghana told The Toronto Star.
Vatican officials received letters reappointing them to the jobs they held under Benedict XVI, who retired Feb. 28, but the officials were told their appointments were only "until further notice," Turkson said.
"If he wants to have certain people in certain places, he needs to have the freedom to do it," said Turkson, a Benedict appointee who received the letter. "All of us understand that."
Turkson told the Star one Curia member he hopes Francis lets go is Secretary of State Cardinal Tarcisio Bertone, who acts as the Vatican's prime minister.
Bertone, 78, was in charge of the Holy See's political and diplomatic activities during a scandal known as VatiLeaks that engulfed the Vatican last year.
Separate scandals under Bertone's watch include reported corruption in the awarding of Vatican contracts that allegedly cost the Holy See millions of dollars due to higher contract prices, as well as alleged money laundering at the privately held Vatican Bank inside Vatican City.