What is most striking about the two Popes being beatified in Rome tomorrow is the extraordinary contrast between them. One could trawl through the long list of Peter's successors and find few such "opposite" papacies.

Pius IX was the longest serving Pope in history. He was elected in 1846 and died in 1878 after 32 years. By contrast, John XXIII was 77 years old a month after he became Pope in October 1958. He died in June 1963. Intended as an interim Pope, he was elected on the 12th count. It was felt he would hold the fort for a few years until agreement emerged on a younger candidate.

But this old man turned out to be one of the most revolutionary and best-loved Popes in history. Before his election, he was not particularly highly thought of in Vatican circles. There, his rise was attributed by some to a series of happy accidents rather than to any particular prowess. Indeed Pope John's view of himself was not too remote from that of his cooler, curial colleagues.

When he was appointed nuncio to Paris in 1944, he thought someone in Rome had made a mistake. At the time he was head of the Vatican diplomatic mission to Turkey where he was generally ignored by both Rome and the Turkish government, though well liked in the diplomatic corps as a genial host and affable dinner guest.

Then as before, and when appointed patriarch of Venice at 71, he believed he had reached the end of the road, so no one was more astonished than himself when he was elected Pope. A conformist all his life, he became a radical old man - in a hurry.

Intent on bringing the church up to date, he announced the second Vatican Council and, in the teeth of sustained opposition from the curia, it opened in 1962. Its purpose was to open the church to the world. For the first time since the Reformation, Anglican and Protestant church leaders were received in the Vatican, and similarly with Eastern Orthodox leaders.

Pope John removed "the perfidious Jew" phrase from the church's Good Friday liturgy and received Jewish visitors in the Vatican. He broke with a tradition, established by Pius IX, of the Pope as "prisoner of the Vatican" and walked freely around Rome enjoying the company of ordinary people of whom he remained one all his life. One of nature's democrats, he was from a family of 13 children who lived on a small farm at Sotto il Monte near Bergamo in Italy.

On his election in 1846, Pope Pius IX began as a great liberal. He declared an amnesty for political prisoners and exiles from the papal states, which he ruled. He abolished the Jewish ghetto and absolved Jews of obligations to attend Catholic sermons every week. All that changed after he was forced into exile in an 1848 coup by Italian nationalists.

Transformed, he returned to Rome in 1850 assisted by the French. He reinstated the Jewish ghetto in Rome, which was all that remained of his previous territories. He denied them basic civil rights and banned them from attending university as punishment for their participation in the 1848 revolution.

In 1858, a six-year-old Jewish boy was forcibly removed from his family by papal police and raised a Catholic in Rome after a servant in his home said she had baptised him. The Pope refused the parents' pleas to return their son. The boy later became a priest.

In 1864 his encyclical Quanta Cura included a Syllabus of Errors which condemned freedom of the press, freedom of conscience and freedom of religious expression. It was an overt attack on the modern world. He approved the execution of two anarchists in Rome and banned Catholics from taking part in Italian politics.

He set up the first Vatican Council in 1870, where he promulgated one of the most controversial Catholic dogmas, that on papal infallibility. It centralised church authority on Rome and on the papacy.

WHEN a cardinal objected that it was contrary to Catholic tradition, Pius IX responded "La tradizione son io" (I am the tradition).

His conservative, authoritarian "ultramontanism", as it came to be known, spread throughout and dominated the church until Pope John XXIII.

Some say it has returned with the current Pope, which gives resonance to a quote from Cardinal Newman in a recent Irish Catholic series on Pope Pius IX by Father Oliver Rafferty SJ, Professor of Ecclesiastical History at Maynooth College.

Two-thirds the way through Pius IX's reign, Cardinal Newman said: "It is not good for a pope to live for 20 years. It is anomaly and bears no good fruit, he becomes a god, has no one to contradict him, does not know facts and does cruel things without meaning."

Pius IX was also responsible for declaring the doctrine of the Immaculate Conception (which holds that Mary was without original sin) and encouraged devotion to the Sacred Heart.

In 1870 he lost Rome and so all his temporal power. He declared himself "a prisoner" at the Vatican and refused to settle terms with the Italian government. That did not happen until 1929 when a deal was done with Mussolini.

When Pius IX's body was being removed to its final resting place in Rome, a mob tried to throw it into the River Tiber. By contrast, it has been said that if the old custom of declaring sainthood by popular acclamation still prevailed in 1963, then Pope John would have been made a saint on his death in June that year.

Whereas there is little surprise at the beatification of Pope John, many people are puzzled at the elevation of Pius IX. It is odd too that the miracle attributed to Pius did not occur until 1986, nor is there an explanation for the 14-year delay since then in his beatification process.

Why the church should beatify him now is a mystery. Perhaps the explanation lies in the very contrast between the two Popes concerned, and possibly it is more than just a question of balance.

There are after all still many at senior levels in the church who regard the reign Pope John XXXIII as something of a travesty.