The world knows Joseph Ratzinger of Germany as Pope Benedict XVI, but Marcello Pera of Italy also knows him as a friend and literary collaborator.

"He's a very decent man, a very bright man, a very profound man - someone who asks a lot of questions, and also listens carefully," Mr. Pera, president of the Italian senate, said yesterday. "We are both deeply concerned with the question, 'Can a civilization exist without any sense of the sacred?'"

That question is examined in their new work, "Without Roots: The West, Relativism, Christianity, Islam." Published by Basic Books, the 160-page volume is less a narrative than a geo-theological exchange on spiritual, cultural, and political crisis in the West.

The protagonists are two learned men - one a former prefect of the Congregation for the Doctrine of the Faith under the late Pope John Paul II, and the other a former professor of philosophy of science at the University of Pisa. Their exchange deals with issues such as European identity; violence and terrorism in Europe; the continent's uncertain relations with America, and the rejection by France and the Netherlands of the E.U. constitution.

The literary collaboration grew out of an invitation Mr. Pera extended to then Cardinal Ratzinger address the 315-member senate on May 13, 2004.

"As far as I know, it was the first time that a cardinal came to speak before the senate," Mr. Pera said.

Cardinal Ratzinger's talk followed by a day a speech Mr. Pera gave at the Pontificia Universita Lateranense in Vatican City.

"Although neither of us knew what the other would be saying, we both wound up with significantly the same conclusions - that Europe's moral and cultural malaise needed to be addressed at a time when much of the continent seemed to have abandoned its spiritual roots," Mr. Pera said.

"So we decided to collaborate on a book that could be presented as a dialogue," he said. "We had numerous discussions in person, and we also exchanged letters."

The cardinal found himself increasingly mentioned as a potential successor to the ailing John Paul II. After his death, Cardinal Ratzinger was elected the 265th pontiff of the Roman Catholic Church, presiding over its 1.1 billion members around the world.

Mr. Pera was born into the church, as the son of Luigi, a railway worker, and his wife Milena. They lived in Lucca, a town in Tuscany.

"My parents were very poor," Mr. Pera said. "But they were determined that I would get a good education."

He attended technical schools, and eventually the University of Pisa, where he obtained his graduate degree. After that, he became an academia.

"I love to write as well as teach," he said. "I held discourses on the philosophy of science, and explored questions about scientific disputes. I found that it was relatively easy to be regarded as an intellectual if nobody understands you - then they think that you're very deep. I preferred clarity, however."

His pursuit of clarity took him to the Universita di Catania in Sicily, then back to the University of Pisa. He was a fellow at the Massachusetts Institute of Technology, and later spent a year at the London School of Economics.

All the while, Mr. Pera's reputation as a philosopher grew. He would frequently bemoan the future of a civilization - Europe - that, in his words, "has abandoned its history for relativist secularism."

It was an intellectual position Cardinal Ratzinger shared. The German had emerged as John Paul II's most influential adviser on theological issues. At the same time, he'd established a reputation as a conservative thinker who often called on the West to embrace a spiritual rather than political renewal, according to Mr. Pera.

"He urged us to accept the moral beliefs that alone can help us to make sense of changes in technology, economics, and society," Mr. Pera said.

But on the matter of personal faith, he diverged with Cardinal Ratzinger, who's been held by many as an exemplar of the church. To this day, Mr. Pera describes himself as a secularist and a nonpracticing Catholic.

Another difference lay in the fact that while the cardinal stayed within the Church, Mr. Pera ventured into electoral politics. As an academia, he'd organized 20 colleagues into forming a reformist movement. Prime Minister Berlusconi's Forza Italia Party persuaded him to run for the senate in 1996.

At the completion of his five-year term, Mr. Pera decided that he could practice politics while continuing as an author and lecturer. He won a second term in 2001, and was then elected as senate president. The position makes him first in the line of accession to the Italian presidency.

"As senate president, I must deal with politics in a nonpartisan manner - because I preside over a senate that has nine parties and groupings," Mr. Pera said. "I set the weekly agenda for a senate that is in session most of the year, with very few breaks."

In those sessions he focuses on issues such as judicial and constitutional restructuring. Assisted by four vice presidents, Mr. Pera has a packed schedule most weekdays.

"My schedule on weekends is also packed," he said.

That's because every Friday evening he boards a train to his native Lucca. At the end of a three-hour ride he faces 300,000 constituents who demand his attention.

His perorations before his constituents are mostly about local and national issues. But Mr. Pera also increasingly talks about anti-Semitism in Europe.

"I hate discrimination - I really hate anti-Semitism," he said yesterday. "And Europe should be doing a lot more to counter the growing anti-Semitism. Today's anti-Semitism is somewhat different from the old hatred of Jews - it concerns the State of Israel. Europe hasn't done enough to guarantee the safety and survival of Israel."

His views will appear in books that Mr. Pera plans to write.

But one book that's already appeared in Italy since his friend Cardinal Ratzinger became pope is titled, "The Europe of St. Benedict."

It consists of essays, and its title points to the Catholic saint who was the founder of Western monasticism.

It's no coincidence a namesake of the saint is now the prelate. It's also noteworthy that Marcello Pera's co-author of "The Europe of St. Benedict" is Pope Benedict XVI.