Living in history is a bit like finding oneself in a shuttered mansion to which one has been brought blindfold, and trying to imagine what it might look like from the outside.

Clearly, after exploring the interior thoroughly, one would be able to recognise that the house is large and very impressive. But it would still be difficult to imagine the appearance of the outside - and impossible to know what it looks like in its setting.

That's where the people of this island are at the moment in relation to the Good Friday Agreement: we know that it is an impressive achievement, but even those of us who have studied it in detail find it difficult to imagine how it will appear later on, when the history of 20th-century Ireland comes to be written. For so far as the present and recent past are concerned, we are still inside history.

Of course we all know intellectually that we are in the middle, and not at the end, of history. But this is not easy for us to recognise emotionally because the history we learn is necessarily about the past, and so we tend instinctively to feel ourselves to be at the end, rather than in the middle, of history.

There are moments, however, which, as they are happening, we recognise to be historic - without knowing quite what historians will ultimately make of them. And this is one such moment.

For myself, I believe that historians will in time see this agreement as one of three seminal or defining moments in 20th-century Irish history - the others being the 1916 Rising and the Treaty of 1921.

Of course there have been many other important moments - the democratic transfer of government in 1932, just nine years after the end of the Civil War; the 1937 Constitution; the 1949 Declaration of a Republic; the civil rights marches in Northern Ireland; the hunger strikes. And there has been at least one false dawn, which many of us at the time identified - wrongly as it turned out - as offering a resolution of the Northern problem, viz, Sunningdale.

But if the hurdle of the May 22nd referendum in the North is surmounted with an adequate majority (I believe that support here will be overwhelming), then the process of finding a way of reconciling the aspirations of the two communities with which history has endowed our island - a process that may be said to have begun with the first Home Rule Bill in 1886 - will finally have been successfully accomplished.

That does not mean that this agreement will have marked the end of Irish history. History has no end, and none of us can foresee how the relationship between the two parts of our island will evolve in the 21st century.

That the violence of the past 30 years has set back the prospect of Irish unity is self-evident. I could not with any seriousness today write the kind of book that I published 26 years ago - Towards a New Ire- land - addressing in practical terms, as a serious, albeit not immediate, possibility, the emergence of a federal Ireland. And if I did, in contrast to 1972, virtually no one now would take it seriously.

There are several paradoxes here. For while Irish unity is excluded in any foreseeable future by the negative impact of IRA violence and of the largely reactive counter-violence of the loyalist paramilitaries, and at times of elements in the security forces, the reaction of the people of this State to that violence is now about to remove a major obstacle to a positive North-South relationship - viz, Articles 2 and 3 in their present form.

For, without the revulsion created by the IRA murdering people in our name, I do not think either parties or people in this State would have been willing to give up the claim on the territory of Northern Ireland contained in these Articles.

Although, curiously, no one commented on this at the time, this paradox of the IRA's unintended role in clearing the way for this constitutional change emerged into view at the time of the Downing Street Declaration.

The Hume-Adams statement had opened the possibility of an end to IRA violence, if the British would make a solemn statement about having no selfish strategic or economic interest in Ireland, and about recognising the right of self-determination of the Irish people - albeit a right to be exercised separately in North and South.

But the inevitable quid pro quo for such a British move was, of course, an unequivocal declaration of the consent principle by the Fianna Fail Taoiseach of the day - Albert Reynolds. Thus it turned out that at the end of the day it was a Sinn Fein/IRA initiative that effectively secured the first unambiguous acceptance by Fianna Fail of the consent principle, which Fine Gael and Labour had felt able to adopt explicitly since 1969.

But there are also fundamental paradoxes on the unionist side. Quite apart from the obvious paradox involved in the conditional character of their nominally fervent loyalty to the United Kingdom, an even more fundamental one is to be found, I believe, in their attitude to the division of our island.

If unionists had mentally accepted the reality of partition, and had felt themselves to be what they in fact became at that point - an unchallenged majority within Northern Ireland - they would have behaved as a secure majority, and would not have felt the need to discriminate against the minority.

But instead of recognising that they enjoyed such a secure majority in their part of the island, Northern unionists in reality never ceased to feel themselves to be a threatened minority in the island of Ireland: in other words, at a deep psychological level their mind-set has remained an all-Ireland one.

The counterpoint of this is, of course, that despite the persistence of the aspiration to Irish unity in this part of Ireland, and despite the genuine concern that exists here for the plight of the people of Northern Ireland, the fundamental loyalty of most people in this part of Ireland is to our own State - rather than to a notional and abstract united Ireland.

This double paradox of Northern and Southern attitudes has tempted me at times to remark that as at the deepest level both the unionists in the North and we in the South have attitudes that are in a sense the converse of those publicly expressed - theirs being based on a sense of being a minority in an all-Ireland situation and ours being founded on a primary loyalty to the 26-county State - it is not all that surprising that the British have until recently found the problem insoluble!

As to the conflicting views of Sinn Fein and the UUP on the significance of this agreement, both their stances contain an element of truth. The UUP is, of course, right to say that the Union with Britain has been made more secure by an agreement under which all the political parties in this State and, I believe, the vast majority of its people, give up the territorial claim on the North and accept unambiguously the principle that the consent of a majority in the North is a precondition of unity.

But Sinn Fein is also right in a certain sense. For the removal of the claim on Northern Ireland in Articles 2 and 3 has opened up a prospect of North/South co-operation which will certainly bring Northern unionists and ourselves closer together. And while no one can say that this will necessarily lead to Irish unity, it is certain that without such a period of co-operation there can be no possibility of this ever happening.