"Marxist ideology as it was conceived no longer responds to the truth today, we can no longer respond this way to construct a society," the pope said.
But the pope said that the "path of collaboration and constructive dialogue," which his predecessor Blessed John Paul II initiated with the communist regime, "is long and demands patience."
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"We want to help in the spirit of dialogue to avoid the trauma and to help move toward a fraternal and just society" in Cuba, he said.
In answer to a question about dramatic inequalities of wealth in Latin America, Pope Benedict lamented what he called a widespread moral "schizophrenia" that stresses personal morality while ignoring social conscience.
"We see in Latin America and elsewhere that not a few Catholics have a certain schizophrenia with regard to individual and public morality," he said. "In their private lives they are Catholics, believers, but in public life they follow other paths that don't respond to the great values necessary for the foundation of a just society."
While that assessment might have seemed to echo left-wing critiques of the oligarchies that dominate the politics and economies of many countries in the region, the pope declined a reporter's invitation to endorse even a non-Marxist, nonviolent version of liberation theology, a movement which he severely criticized as head of the Vatican's doctrinal office in the 1980s and '90s.
"The church is not a political power, it is not a party," the pope said. "It is a moral reality, a moral power."
Accordingly, the pope said, "the first job of the church is to educate consciences ... both in individual ethics and public ethics."
He called for promoting Catholic social teaching even to nonbelievers by an appeal to a "common rationality" which he said could overcome social divisions.
To a reporter from Mexico, who said the fighting among traffickers has killed an estimated 50,000 people over the past five years, Pope Benedict said that the church has a responsibility to "unmask evil, unmask the idolatry of money that enslaves man" as well as the "false promises, the lie, the swindle that lie behind drugs."
"We must see that man has need of the infinite," the pope said. "To make present the goodness of God, make present his truth, the true infinite for which we thirst, is the great duty of the church."
The meeting with reporters, which lasted slightly over 20 minutes, ended on a light note with the presentation of gifts to the pope.
One local journalist gave the pope a silver medal struck to commemorate his visit to the central Mexican state of Guanajuato, a silver mining center. Another journalist, noting the pope's recent encounters with modern information technology in the form of tablet computers and Twitter, gave him an iPod loaded with Mexican and classical music to entertain him on the flight.
After a 14-hour flight from Rome to Mexico, the pope was scheduled to visit the Archdiocese of Leon March 23-26. The flight will have taken him across seven time zones, to a city 6,000 feet above sea level. From Mexico, he will fly to Cuba, to visit Santiago de Cuba and Havana March 26-28. He will arrive back in Rome March 29 after a 10-hour flight.
It will be his third visit to the Americas, after the United States in 2008 and Brazil in 2007.