The Catholic Church has launched the official process which may culminate in a sainthood for the late Pope John Paul II with a service in Rome.
John Paul II did much to speed up the canonisation process
The mass to nominate John Paul for beatification marks the penultimate step on the path to becoming a saint.
Members of a special commission - including a latter-day "Devil's Advocate" whose job is to challenge any claim - swore secrecy and probity.
The commission will sift possible evidence of a miracle by the late Pope.
During the mass at the cathedral of St John Lateran, the words of Cardinal Camillo Ruini were interrupted by applause and chants from the gathered worshippers.
"Any words that I can now add [...] seem superfluous, so great and universal is the knowledge of him and so profound and unanimous the conviction of his saintliness," Cardinal Ruini said.
His case is being fast-tracked after Pope Benedict made a special ruling.
Normally, the procedure does not start until five years after death. Pope John Paul died less than three months ago.
John Paul himself had made an exception for Mother Teresa, two years after she died.
In the past, the BBC's Jeremy Bowen says, the process could take centuries.
Emails pour in
To canonise the late pontiff, the Vatican must find evidence of at least two miracles since his death - miraculous acts proven to have happened after a direct appeal to John Paul through prayer.
Popular title for official formally known as the Promoter of the Faith
Required to prepare in writing all possible arguments against canonisation
The post dates back to the early 16th Century
John Paul abolished the post in a 1983 review of canonisation procedure
Hundreds of letters and e-mails in praise of John Paul's holiness have already arrived, the Vatican said.
The Rev Giuseppe D'Alonzo, promoter of justice for the Diocese of Rome, will have the task of questioning such evidence.
Although he performs the duties of the Devil's Advocate, that actual post was done away with by John Paul in 1983 when he moved to simplify the process of canonisation.
Asked what he thought about making John Paul II a saint, the Rev D'Alonzo replied that it was not for him to decide, only to "verify the truth".
Monsignor Slawomir Oder, the main advocate for the late Pope's case, said last week he had received statements from across the world, with about 100 e-mails filling his inbox every day.
If a miracle is established, John Paul may be beatified, while a second miracle must then be proved for full canonisation.
As well as reading statements from believers, the commission will investigate John Paul's words and deeds to establish that he led a holy life.