By Philip Pullella
VATICAN CITY (Reuters) - Pope Benedict urged lapsed and lukewarm Roman Catholics on Thursday to rediscover their faith but acknowledged there are "bad fish" in the Church itself.
The pope made his comments at two large events before thousands of people in St. Peter's Square on the 50th anniversary of the opening of the Second Vatican Council, a far-reaching event in the Church's 2,000-year history.
"Recent decades have seen the advance of a spiritual desertification," he said in his sermon of a morning Mass, opening a worldwide "Year of Faith".
"We see it all around us ... the void has spread," he said.
The mass was attended by hundreds of Roman Catholic bishops as well as representatives of other Christian churches, such as Archbishop of Canterbury Rowan Williams. The bishops are in Rome for a synod, or conference, at the Vatican aimed at building a strategy to bring lapsed Catholics back to the faith.
Later, on Thursday evening, the pope made an impromptu address from the window of his apartment overlooking the square and made references to the sexual abuse scandal and conflict within the 1.2-billion-member Church.
"In these years, we have seen that there is discord in the vineyard of the Lord, we have seen that in the net of Peter (St Peter, the first apostle) there are bad fish, that human fragility exists even in the Church," he said.
"The ship of the Church is navigating in strong headwinds, in storms that threaten the ship and sometimes we have gone as far as thinking that God is sleeping and he has forgotten us," he said.
Pope John XXIII convened the Second Vatican Council 50 years ago to bring the Church up to date with the modern world.
During the Council, which ended in 1965, nearly 3,000 bishops from more than 100 countries wrote 16 documents on various aspects of Church life and mission and urged more "collegiality," or sharing of responsibility, between the pope and bishops.
Among its innovations was the introduction of the Mass in local languages after centuries of it being said in Latin.
The Council also encouraged dialogue with, and respect for, other religions and repudiated the concept of collective Jewish guilt for Jesus' death, revolutionizing Catholic-Jewish relations after 2,000 years of mistrust.
But 50 years on, the Council is divisive. Liberals in the Church say Benedict, who attended the Council as a young priest, has turned back the clock on some Council reforms and moved to centralize power in the Vatican again.
Conservatives praise him for correcting what they regard as errors in applying its ideas. For example, conservatives assert that the Council's push for dialogue with other religions went too far and weakened the traditional teaching that Catholicism is the one true faith.
(Reporting by Philip Pullella; Editing by Michael Roddy)