If the defining question of a past generation was Where were you when you heard that John F Kennedy was shot?, the defining question of this generation will be Where were you when you heard that the Word Trade Centre was attacked? International terrorists who once only threatened Americans outside the United States are now operating on American soil. Most terrorist organisations operating in the 1970s/80s had clear political objectives. They calibrated their attacks to produce just enough bloodshed to get attention for their cause without alienating public support.
Today a growing percentage of terrorist attacks are designed to kill as many people as possible. This trend reflects the changing motivation of today's terrorists. Religiously motivated groups such as bin Laden's Al-Quida are driven by a vision of a post-apocalyptic future or simply by ethnic hatred.
Such groups lack a concrete political goal other than to punish their enemies by killing as many of them as possible, without any concern for alienating sympathisers.
The horrific, almost surreal, sight of passenger airlines being flown into the twin towers of the World Trade Centre will remain permanently etched on the minds of an entire generation.
It was the ultimate example of how vulnerable any country, even the world's most powerful one, can be to terrorism. We on this island know better than most how a small group of determined and fanatical extremists can threaten and frustrate a democratic society.
Perhaps the most frightening aspect of last Tuesday's vile atrocity is that such carnage could be inflicted without use of missiles, explosives or armaments.
In place of these, the terrorists found an extremely lethal cocktail: knowledge and absolute conviction. The knowledge was the ability to fly a commercial jet. The absolute conviction was the belief that the cause was right and that your sacrifice will be rewarded in the next life.
These two elements produced a terrorist weapon as deadly and devastating as any tactical warhead or nuclear device. There is no technological gizmo, contraption or weaponry that can deal effectively with a weapon of such power. The blind and unyielding belief that your cause is right and that God is on your side is something that will not be countered by military means alone.
The people who carried out the attacks on the World Trade Centre and the Pentagon were cruel and cold-bloodedly determined. Those who trained and directed them are evil. We may speculate as to their specific identities. Given the magnitude of was occurred and the planning and preparation required, it is possible that there was more than just the one master mind. Whoever it was, there is a need to establish clearly and publicly who was behind this attack.
The shift in terrorist motives has contributed to a change in the way international terrorist groups are structured. Because groups driven by ideological/religious motives lack a political or nationalistic agenda, they have less need for hierarchical structures.
Instead they rely on loose common cause, affiliations with like-minded groups from a variety of countries. These loose transnational terrorist networks are difficult to track, penetrate or predict.
That there will be a military retaliation is without doubt. That such retaliation is imminent is clear. We can already see the major TV news networks dust off their Gulf War charts and diagrams.
There is towering anger, horror and frustration, not just in the US but throughout the world. Almost every person in the Western world has felt a little less safe and a little more threatened since last Tuesday.
The attack has produced messages of sympathy and condemnation from countries previously unsympathetic to the US, such as North Korea, Palestine, Libya and Iran. A new broad world coalition against such terrorism could arise out of the ashes of this disaster.
There is the potential to muster a very broad base of support behind the measures required to deter others from such attacks, based on the central premise that humanity is the loser.
Any military retaliation must be properly thought out before it is carried out. An ill-conceived response, which is seen as disproportionate or targeted against innocent people, could produce an aftermath that widens the split between the Western and Islamic worlds and simply drives more recruits into the arms of the extremists.
Other response options, diplomatic, economic and political, exist in addition to a military one. The response must be seen as the international community taking justifiable and considered actions against those who are conclusively guilty of ordering these offences. It must not be seen as just the US, NATO or the Western world unilaterally targeting Islamic states.
There is a dangerous divide between the Islamic and Western worlds. It is not a new one, it has always existed. Increasing globalisation coupled with a shrinking world have brought the two into closer conflict. Cultural and historical conflicts have fostered an atmosphere of mutual mistrust and misunderstanding. We must not engage in actions that will widen that gulf.
The 1964 Johnson/Goldwater US presidential campaign saw one of the most powerful political broadcasts ever made. Sometimes referred to as the Daisy Girl, it showed a young girl counting the petals on a daisy. Just as she reached nine the camera zoomed in on her eye. Her voice was faded out to be replaced by that of a man counting down the launch of a nuclear missile.
As the count reached zero, a giant mushroom cloud appeared on screen as Lyndon Johnson's distinctive Texas drawl was heard saying: "These are the stakes: to make a world in which all of God's children can live. . . or to go into the darkness. We must either love each other, or we must die." Perhaps it is overly dramatic, but I get the feeling that this is the choice facing us today.
Willie O'Dea is a Fianna Fβil TD for Limerick East and Minister of State at the Department of Education