The Pope said Castro, who was raised a Catholic, asked about the reasons for the changes in the liturgy after the Second Vatican Council, about the role of the Pope and about the pope's thinking about the larger philosophical questions weighing on the minds of people today.
The meeting lasted about 30 minutes, Father Lombardi said, and the questions were an indication that "now his life is one dedicated to reflection and writing."
On the liturgy, the Pope said Castro told him, "It's not the Mass I knew in my youth."
The more philosophical topics included Castro's curiosity about how the church is handling the ethical challenges posed by scientific and technological developments and the relationship between faith and reason, as well as the pope's concerns about a growing number of people who don't believe in God or act as if God does not exist, Father Lombardi said.
"In the end, Commandante Fidel asked the Pope to send him a few books" dealing with the questions he had, the spokesman said.
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Father Lombardi also said Castro had told Pope Benedict that he had followed the pope's entire visit on television, and Castro had remarked that he and the Pope were about the same age. The Pope will celebrate his 85th birthday in April, and Castro will turn 86 in August.
The Pope said he told Castro, "Yes, I'm old, but I can still carry out my duties," Father Lombardi said.
In a statement published on the government's papal visit website, the former president had said he would be "very pleased" to meet Pope Benedict.
"I decided to ask for a few minutes of his time," although he said he realized the pope's schedule in Cuba March 26-28 was rather full.
Castro had met Blessed John Paul II twice: first in 1996 at the Vatican and then in 1998, when the late Pope visited Cuba.
When Castro arrived at the nunciature to meet Pope Benedict, Father Lombardi said, he was greeted by Cardinal Tarcisio Bertone, Vatican secretary of state. The spokesman said Castro told the cardinal "he was so happy" about the beatifications of Blessed John Paul and of Blessed Mother Teresa of Kolkata, whose order has done much for Cuba.
Father Lombardi said Castro was accompanied by his wife, Dalia, and two of his daughters.