War is not just an activity. It is also a system. It is an economy, a politics, an ideology, a principle around which a society is organised. It shapes the choices, sets the agenda, imposes a system of values. It doesn't just reflect the existence of antagonistic tribes, it creates those tribes themselves.
When states and nations and subject peoples ask themselves who or what they really are, more often than not they find their answers in war - battlefields, acts of military heroism, doomed rebellions, relentless sieges. They imagine themselves enacting identities forged in the heat of war.
As we prepare for next week's peace talks, it is well to remember this. For if war is not just an activity, then peace cannot be just the absence of that activity. The absence of violence may be the precondition of peace talks, but it is not in itself a sufficient outcome. And it is well to remember, too, that the end of war is the end of a whole system of social organisation.
It is not "the restoration of normality", but the destruction of what has been, for a long, long time, the norm. Thirty years of violence has given Northern Ireland a grim stability, polarising opposites, enforcing rigid divisions, creating one of the most heavily policed societies on earth.
Peace is, in such circumstances, a subversion of the given order of things. Behind all the cliches about taking risks for peace, there is the reality that peace itself is a risky business. It threatens the systems of war that have shaped Northern society for three decades. It undermines economies, ideologies and political systems that have been remarkably durable.
Language tends to obscure this truth. Peace tends to be associated with passivity, with rest and quietness. It should, rather, be envisaged as a strenuous activity, a noisy, never-ending struggle.
The American religious activist, Jim Wallis, has given a good description of a night in 1978 when he and fellow campaigners were lying down on railway tracks in Colorado, blocking the path of trainloads of plutonium bound for a factory making the triggers for nuclear bombs. They were soaked by heavy rain, which then turned to sleet and snow.
Chilled to the bone, they were in real danger of dying from hypothermia, but some of them decided to stay. And through the long, sleepless night, Wallis realised that their struggle for peace was curiously warlike.
"My mind," he wrote later, "was filled with images of soldiers who had for centuries braved the elements, endured hardship, risked injury and death, given up their lives in order to wage war. Then it dawned on me. Why should we expect the cost of peace to be less? What would happen if we were to `wage peace' with the discipline, sacrifice, and even willingness to suffer that so many have accepted to wage war?
"Peace, I realised that night, would not be achieved simply because it is a better idea than war, but only when a sufficient number of people pursue it with the same commitment and determination."
Peace in Northern Ireland has always been a better idea than war, but it has never been pursued with the commitment and determination that the warmongers have mustered. One of the daunting and depressing realities of Northern Ireland on the eve of the talks is that very few people have, in this sense, waged peace.
We know that in modern western societies it is possible for peace movements to have a huge impact on events.
It happened in America during the Vietnam war. It happened in Europe in the early 1980s when the nuclear disarmament movement made a huge contribution to the ending of the Cold War. But in spite of some brave attempts and of the unsung work of many marvellous people, it never really happened in Ireland.
Groups such as the Peace People and the Peace Train committee had moments of great significance. Spontaneous revulsion at atrocities such as Enniskillen, Warrington and Greysteel seemed, for a time, to be capable of forcing change. But the desire for peace never really became a demand for peace. The political cost of inflicting violence on the other side never quite outweighed the political benefits that you could reap from doing so. Most people wanted peace - very few waged peace.
THE awkward truth is that the killers and maimers, the kneecappers and torturers, the bombers and snipers, the gung-ho enforcers and righteous crusaders, have shown more courage, more fixity of purpose, more willingness to sacrifice and endure, than almost all of the rest of us put together.
Our desires were passive - we wanted it all to stop, to go away, to get out of our faces and off our screens. Theirs were active: time and again, they intervened effectively in the course of events. Against our despair, their certainty won through every time.
It would be good to think that the talks are happening because the combatants have been forced to the table by the public demand for peace. But let's not delude ourselves. The peace is not of our making, but of theirs. They started a war which had to end in negotiations rather than victory for either side, simply because no victory was available.
The opportunity for a settlement arises from a combination of their fatigue, and the changing nature of world politics. The war hasn't been stopped, it has ended. It ran its natural course, and the rest of us - civil society, the community, the Irish people, whatever you want to call us - never managed to shorten that course.
And because that is so, the system of war remains intact. The politics, economics, ideologies and structures of war go on - only the activity itself has ceased. What this means is that the rest of us still have to do what we never managed to achieve while the killing was going on - to wage peace, to challenge with courage and commitment the system of war.
We have to be willing to dismantle the normality that has sustained violence over the last three decades. We have to take the risks that we never really took when the killing was in full swing.
For people in the Republic, that means giving up some cherished assumptions about the nature of Irishness. It means an end to the comfortable definition of "us" as a homogeneous, sharply defined people, an end to tribalism. It may well involve a willingness to rethink the relationship of Ireland as a whole to Britain.
And it will certainly involve a public demand that the Government approaches the negotiations, not as a State manoeuvring to further its interests, but as a nation waging peace with all the single-minded determination that nations usually bring to the waging of war.
Fintan O'Toole is temporarily based in New York