The unexpected resignation of Pope Benedict XVI still resonates deeply even after two or three days of trying to take it in.
There have been many historic events in my lifetime, including a man on the moon and the collapse of the Berlin Wall, but I never dreamt that I would live to see a Pope resigning.
It has shocked Irish Roman Catholics just as much as their co-religionists elsewhere and people of Protestant denominations and of other faiths, as well.
This sense of shock is similar to that which everyone would feel if the Queen Elizabeth suddenly said "I'm off. I've had enough." The abdication of her uncle, Edward VIII, traumatised Britain in 1936 and it is still embedded in the national psyche.
This Pope's resignation is another massive historical event. Traditionally, Popes do not 'do' resignations, apart from Gregory XII, who was forcibly 'resigned' by his enemies 598 years ago in 1415, due to a schism in the Church.
No schism was apparent this time and, if there was, the Pope and his colleagues kept it quiet. The reaction in Rome was "incredulous", according to the Vatican spokesman, Fr Federico Lombardi. There is inevitable speculation about the 'hidden' reasons for the Pope's resignation and many believe that the inside story has yet to be told. The real reason may be that he is simply an elderly man who does not have the strength to continue in this taxing post.
As the Church of Ireland Primate, Archbishop Richard Clarke, pointed out, the Pope recently told residents in an old people's home, "I am here not only as your Bishop, but as an old man in the company of other old people."
Significantly, the Pope – like the former Anglican Primate, Dr Rowan Williams, who also stepped down recently – has sent out a strong message that leadership of a world church is an impossible task for any individual and that it can no longer be regarded as a lifetime role.
This may open up other spheres of leadership, perhaps even within British royalty itself. Until Monday, no one thought that a Pope would resign – especially after the long illness of John Paul II, who carried on when he was no longer capable of doing the job. Now anything is possible.
Pope Benedict's resignation is also a story of unfinished business in the pontificate of this charming, yet conservative, leader, who leaves much baggage – including clerical child sex-abuse – to burden his successor.
His departure has shocked the Church, but not floored it, because the powerful Vatican civil service knows how to hold on to power and will grimly do so again.
Now the attention will turn to a successor. Will there be a Latin-American, Asian, or African Pope? No one knows – in spite of the endless commentators who fill air time with speculation. Usually those who are 'favourites' for the Papacy are passed over, anyway.
We are all moving into uncharted territory, but the Catholic Church will still carry on doggedly, come what may, in its self-appointed role as the supreme guardian of the Christian faith. Even so, it faces a big challenge in filling an unexpected vacancy so quickly.
However, there is one element to Pope Benedict's resignation that changes things forever. Cardinal Brady and other senior clerics have spoken kindly of his humility and courage in resigning. This is true.
But Benedict has unexpectedly dismissed the centuries-long assumption that a Pope chosen by God dies in office, whatever his health. He has changed all that and nothing in the Catholic Church, or world religion, will ever be the same again.
This most conservative of Popes has amazed, surprised and totally thrown all of us.