"The message of Fatima invites us to trust" in Christ's promise that the final victory is his, the cardinal wrote in a commentary on the secret, which was released Monday at the Vatican.
In a 43-page booklet, the Vatican published photocopies of Carmelite Sister Lucia dos Santos' handwritten texts of the secrets she said was revealed to her and her two small cousins when the Blessed Virgin Mary appeared to them in Fatima, Portugal, in 1917.
The booklet also included Cardinal Ratzinger's commentary on the text and an explanation of why some church officials believe a key part of the secret refers to the 1981 attempt to assassinate Pope John Paul II.
In the third part of the secret, which has been kept at the Vatican since 1957, Sister Lucia wrote of "a bishop dressed in white, we had the impression it was the Holy Father," going up a steep mountain toward "a big cross of rough-hewn trunks" with other bishops, priests, and religious.
"Before reaching there, the Holy Father passed through a big city half in ruins and prayed for the souls of the corpses he met on his way," Lucia wrote."Having reached the top of the mountain, on his knees at the foot of the big cross he was killed by a group of soldiers who fired bullets and arrows at him."
The others walking with the pope are also killed and angels standing beneath the cross gather the blood of the martyrs, put it in "a crystal aspersorium," as if it were holy water, "and with it sprinkled the souls that were making their way to God," she said.
At a Vatican press conference Monday, Ratzinger said, "There does not exist an official definition or official interpretation of this vision on the part of the church."
Like any private revelation approved by the church, the cardinal said, the Fatima message "is a help which is offered" to Catholics for living their faith, "but which one is not obliged to use."
In the commentary he wrote that the vision described the path of the church through the 20th century as a Way of the Cross, "a journey through a time of violence, destruction, and persecution."
The cardinal said he believed the particular period of struggle described by the vision, culminating in the attempt to assassinate Pope John Paul II, has ended, therefore making it appropriate to reveal the secret's contents.
Lucia, the cardinal wrote, said the Vatican's "interpretation corresponded to what she had experienced and that, on her part, she thought the interpretation correct."
According to the booklet, Pope John Paul sent Archbishop Tarcisio Bertone, secretary of the doctrinal congregation, to Portugal to review the Vatican interpretation with Sister Lucia.
In a letter to the cloistered nun, the pope said, the archbishop "will come in my name to ask certain questions about the interpretation of the third part of the secret. You may speak openly and candidly to Archbishop Bertone, who will report your answers directly to me," the pope wrote.
Bertone said the letter was read to Lucia April 27, then she read it again herself.
The archbishop also gave Lucia an envelope containing what she confirmed as the message she had written in her own handwriting.
Lucia "repeated her conviction that the vision of Fatima concerns, above all, the struggle of atheistic communism against the church and against Christians and describes the terrible sufferings of the victims of the faith in the 20th century," Bertone said.
The archbishop said he felt he had to ask Lucia why she had given instructions that the secret should be revealed only after 1960, an instruction many people claimed was an order that it be published then.
Bertone asked Lucia if Mary had fixed the date.
"Sister Lucia replied: 'It was not Our Lady. I fixed the date because I had the intuition that before 1960 it would not be understood," the archbishop wrote.
Lucia also told the archbishop that while she was given the vision, it was up to the pope to interpret it.
The Carmelite continued having visions of the Virgin Mary and hearing messages from her as late as the 1980s and perhaps beyond, the archbishop said.
The Vatican's booklet containing the text of the secret included the May 13 announcement by Cardinal Angelo Sodano, the Vatican secretary of state, that the pope had ordered the publication of the secret and that he believed the vision referred specifically to the 1981 attempt on his life.