Pope Benedict XVI urged Christians to make their voices heard in France and other countries that have strong traditions of secularism, saying Friday that politics and religion must be open to each other.
The pope embarked Friday on a four-day trip — his first to France as pontiff — that will take him from the presidential Elysée Palace to the Roman Catholic shrine in Lourdes.
Benedict was greeted by President Nicolas Sarkozy and his wife, Carla Bruni-Sarkozy, at a Paris airport, where a military band in plumed hats played a fanfare.
Later in Paris, the pope was to address a gathering, including Muslim leaders, on the second anniversary of a speech that heightened tensions with much of the Islamic world.
Traditionally Roman Catholic France is wrestling with its changing religious landscape, and how to reconcile it with the secularism that underpins the modern French Republic.
The country has a growing number of Muslims whose visible customs, such as wearing headscarves in public schools, have raised the hackles of officials determined to preserve the boundaries between church and state.
On the plane, Benedict expressed understanding for secular traditions, but added that, nonetheless, "religion and politics must be open" to each other.
"The presence of Christian values is fundamental for the survival of our nations and our societies," he said.
Sarkozy pushes "positive secularism"
In a speech after talks with the pontiff at the Elysée Palace, Sarkozy promoted his idea of "positive secularism" — upholding the separation of church and state, while considering religions as beneficial for society and not a danger.
The French president said positive secularism could allow for a dialogue "on the meaning we want to give to our existences."
Similar comments have raised the hackles of Sarkozy's critics in the past.
Secularism is so firmly entrenched here that one prominent politician, centrist Francois Bayrou, even questioned Sarkozy's decision to invite the pope to the Elysée Palace, saying that government and religion don't mix.
In a speech following Sarkozy's, the pontiff said he was convinced of the need for "new reflection on the true meaning and importance" of separation of church and state.
The pontiff said it was "fundamental on the one hand, to insist on the distinction between the political realm and that of religion in order to preserve both the religious freedom of citizens and the responsibility of the state towards them."
But he added that societies must also be "more aware of the irreplaceable role of religion for the formation of consciences and the contribution which it can bring to — among other things — the creation of a basic ethical consensus within society."
2nd anniversary of controversial speech
The pope's agenda for later Friday included a vespers service at Notre Dame Cathedral, meetings with representatives of France's Jewish community and a speech before cultural figures and Muslim leaders.
His stay in the French capital coincides with the second anniversary of his speech about Islam that offended many Muslims.
In the pope's 2006 Regensburg lecture to theologians in Germany, he quoted a 14tm-century Byzantine emperor who was explaining why spreading faith through violence is unreasonable.
The pope has said he is sorry for any offence his Regensburg remarks caused, and the rector of the Paris Mosque, Dalil Boubakeur, said he considers the incident closed.
"Through his speeches we know that he is a man of peace and dialogue," Boubakeur said.
France has Western Europe's largest population of both Jews and Muslims. Despite its Catholic roots, fewer than five per cent of the nation's 62 million people attend mass every week, according to a 2006 poll, and some of its centuries-old cathedrals are crumbling in towns that lack money or the motivation to fix them.
Pope not looking for miracles at Lourdes
The pope's trip to France grew out of his desire to visit the Lourdes shrine in southern France near the Pyrenees while the sanctuary celebrates the 150th anniversary of apparitions of the Virgin Mary to a local 14-year-old, Bernadette Soubirous.
The shrine draws six million people annually, some of them disabled or desperately sick, many of them hoping for a miracle.
The Catholic church has recognized as miraculous 67 healings linked to Lourdes from 1858 to the present.
Benedict told reporters on the plane: "We don't go to Lourdes looking for miracles. The love of the mother (Mary) is the true healing."
Lourdes was the last trip abroad for Benedict's predecessor, John Paul II. When John Paul visited in 2004, he was 84 and suffering the final ravages of Parkinson's disease. He needed to be helped by aides. He died in 2005.