The election of a new Pope is a time for the Church to take stock and look to the future.
After the lengthy papacy of John Paul II, many will see this as an opportunity for the new leader of the world's one billion Catholics to reconsider some of the spiritual and moral issues that caused so much controversy in the latter part of the 20th Century.
Changing times for the Catholic Church
Beyond matters of doctrine, the rapid growth of the Church in the developing world means that many of the faithful are now to be found in countries where poverty is common and where human rights may be lacking. Is the role of the Church purely spiritual? To what extent should it have a social agenda and engage in politics?
There is also pressure from the grassroots for radical changes in the internal organisation of the Church. The key question is where power should lie. Should the Vatican bureaucracy retain centralised control? Or should power be devolved to the bishops around the world?
At this crucial moment in the history of the Church, even the role of the papacy is now up for discussion. The cardinals will have much to contemplate as they make their choice.
The Catholic Church has never been short of critics, and there are those both within and without who see this as an institution in crisis.
They accuse it of failing to recognise the changing attitudes in modern society which have led many, especially the young, to question its traditional views on morality. Marriage is no longer seen by many people as a prerequisite for family life.
The continued opposition of the Church to artificial birth control falls on many deaf ears. And the impact of the women's movement on gender politics has made the Vatican look like the last bastion of inequality.
Many faithful are now found in the developing world
Critics point to a decline in the number of people going to Mass in many Western nations as evidence of a Church out of touch with a large section of its congregation.
A fall in the number of young men entering the priesthood is another cause for concern. In the United States the Church has even resorted to advertising to try to fill the empty places in the seminaries.
The blame is placed on the disappointment felt by many Catholics over the failure of the Vatican to deliver anticipated reforms - notably in its teaching on contraception. The rapid spread of HIV/Aids in many parts of Africa has given this debate a new urgency, and has led to new demands for the Church to sanction the use of condoms as a public health measure.
The Church's insistence that its priests should remain celibate, and the refusal to admit women to the priesthood, are also cited as key issues.
Another crisis for the Vatican has been the sex abuse scandal, notably in the United States. It was bad enough that priests were able to molest children, in some cases for many years, but the revelation that senior clerics tried to cover up the problem has also caused great damage to the image of the Church.
Yet in many parts of the developing world, the Church appears in vibrant health. In many African countries, for example, churches are packed and priests are hard pressed to keep up with the flow of converts.
Strategy on faith
But how should the Church respond to the needs of its global flock? In Latin America, where the number of Catholics has also grown very rapidly, the Church has been divided over what has become known as liberation theology.
By invoking the mission of Jesus, as a friend to the poor, it encourages disadvantaged people to free themselves from economic and political oppression.
The Vatican has taken a tough line against priests and bishops who appear to be supporting revolutionary change, seeing it as a form of social action tinged with Marxism.
Pope John XXIII aimed to modernise the Church
But the issue has not gone away, and the authority of the new pope will be tested as he responds to these tensions. He will be only too aware of the reality that millions of Catholics in the developing world live in poverty, with few of the advantages taken for granted in the developed nations of the West.
One thing is certain - a new pope from Latin America or Africa, would add a new dimension to a fierce debate within the Church about where its priorities should lie in the 21st Century.
The papacy of John Paul II saw the collapse of Communism. In the battle for souls today, the challenge in many parts of the world comes from Islam.
Traditionalists versus progressives
Whoever eventually emerges from the conclave as Pope, the cardinals will be giving careful thought to the role of the papacy in the 21st Century. The Vatican's civil service, the Curia, will also be under scrutiny.
Many in the Church remember the heady days of the Second Vatican Council, when Pope John XXIII "flung open the windows of the Vatican" and let in the winds of change.
At the heart of this process of modernisation was collegiality - a move to give the bishops a much greater say in the running of the Church.
But what has happened since has disappointed the progressives. They see the Church being run by a rigid, centralised bureaucracy that is resistant to change, unwilling to relax its grip on power, and too quick to silence dissident theologians.
Needless to say, traditionalists at the Vatican regard their role rather differently. They stress the need to defend the teachings of the Church at a time when spiritual and moral values are under attack.
But others believe that the centralising tendency in the Church has been a serious obstacle to Christian unity, and argue that reforming the papacy and the Vatican bureaucracy is essential if further progress is to be made towards reconciliation.
And there is a feeling among many cardinals and bishops that the new pope should preside over a less authoritarian Vatican. Some believe that a move towards greater democracy within the church should extend to the process of electing a pope.
Why restrict the choice to an elite group of cardinals? Surely, they argue, to prevent the bishops from having a say in the election. If they get their way, they will overturn hundreds of years of tradition and ensure that this is the last old-style conclave.
So, one way and another, the Catholic Church and its new pope face enormous challenges at the dawn of the third millennium.