History is full of lost opportunities, frequently with tragic consequences. Failure to prevent the second World War cost 55 million lives, not to mention forced population movements.
Ireland's story has been anything but a smooth progression over the centuries to a better world. The anguish of leaders, in whom popular trust was placed, when they realised that the world they grew up in or the ideal they wanted to see realised was gone for ever, is palpable in the pages of history.
Take Hugh O'Neill, earl of Tyrone, writing from exile in Rome to Philip III of Spain, pleading for help, as his ancestral lands were being redistributed irrecoverably amongst new settlers. William Drennan, founder of the United Irishmen, wrote a melancholy poem in 1807 about how independence had flashed before him, and then all had turned to darkness.
In 1921 Lord Carson expressed bitter disillusionment at how unionism had been cynically used by the Tory party in Britain to gain and hold power, but ultimately abandoning the Union, as it had existed from 1801, and its supporters outside the six Ulster counties. Terence O'Neill murmured late at night, while attending a British-Irish Association Conference: "It is all so sad".
Hawarden, in Clwyd near the English border, was Gladstone's country residence, famous for the "Hawarden kite", as the inadvertent leak by his son of his conversion to Home Rule was described. The castle is still a private home of the family, though the park is open to the public. Fifty years intermittently in cabinet and four times prime minister, Gladstone lived in an age when political leaders still had time to read, write and reflect. Disraeli wrote some famous novels that are part of the English literary canon.
Gladstone was strongly religious, though his political opponents regarded him as a pious fraud. Disraeli famously once described him as "a sophisticated rhetorician inebriated with the exuberance of his own verbosity". Queen Victoria detested him. Even his long-suffering wife, Catherine, complained: "If you weren't such a great man, you'd be a terrible bore."
In St Deiniol's church, a memorial with recumbent statues of Gladstone and his wife lies beneath windows depicting three Old Testament prophets, Ezechiel, Jeremiah and Isaiah. At his funeral in Westminster Abbey in 1898, the closing hymn was Oh God, our help in ages past.
Described in the church guide by his descendant, Sir William Gladstone, as "perhaps the greatest lay Anglican as well as the greatest statesman of his day", in choice of hymns as well as prophets Dr Paisley and Mr Gladstone have something in common, though politically coming from opposite directions.
As far back as 1845, Gladstone had a premonition expressed in biblical terms of the role Ireland would play in his future life, "that cloud in the west, that coming storm, the minister of God's retribution upon cruel and inveterate and but half-atoned injustice". His only comment on being summoned by the queen in 1868 in between felling a tree was "My mission is to pacify Ireland".
It was not his fault that he did not succeed, and assembled Redmondites should remember it was not Patrick Pearse who defeated or frustrated the enactment of any of the three Home Rule bills, which could have been a serious and lasting compromise between unionism and nationalism.
In the grounds of St Deiniol's Library is a redundant statue of the Grand Old Man, with a female figure and stringless harp at the base, which had been destined for a provincial Irish town, following Home Rule. By the early 1930s, faced with trouble in India encouraged by Irish independence, George V conceded how misguided their opposition to Gladstone had been. The residential Gladstone Library, St Deiniol's, has at its core his collection of 30,000 books. According to the librarian, the main visitors from Ireland are Protestant ministers of religion, consulting the divinity section.
There are also Gladstone's books on Ireland, the 1798 rebellion and the Act of Union. At the back of one book, The Sham Squire, in his own handwriting is a list of names under the heading "Pecuniary Corruption", top of which was Lord Downshire, owner of Hillsborough Castle. A former British Conservative, Quentin Davies, once told me the greatest mistake the British made in Ireland - a rich menu - was to abolish the old Irish parliament.
The biography by James Kelly of Sir Edward Newenham MP illustrates the limitations of a radical Protestant patriotism that turned reactionary, because of a bigoted and self-interested denial of the rights of Catholics for fear of a Catholic Ascendancy where a majority would dictate to a minority (instead of the other way round!).
He admired America for being a Protestant country true to the ideals of the Glorious Revolution. The Irish Volunteers established by the Ascendancy was as potent a source of the paramilitary tradition as the Whiteboys. Newenham saw them as key, because they would cause "the minions of power to shrink before you".
The past cannot be altered, as Peter Robinson rightly told the Small Firms Association on Tuesday. He quoted a famous passage from The Rubaiyat of Omar Khayyám. ("The moving finger writes").
All that we can do in our own generation is to try and avoid repeating the mistakes and take up the new opportunities that present themselves to us, to create a future of peace and co-operation that many despaired of ever seeing.
It is a daunting prospect for any party to break with the political habits of the past, and to take on responsibilities of government, having for so long played ruthless opposition to the constructive efforts of others. Many will be waiting to see if a new burst of Old Testament zeal has a role to play in pacifying Ireland.