The prospect of a "cycle of retribution", involving the United States and its allies on one hand and Islamic fundamentalists and even states on the other, was the bleak scenario outlined by Prof Terry Karl of Stanford University, a leading US expert on international relations, at an intensive European University Institute seminar this week devoted to analysing the consequences of the September 11th attack on New York.
The seminarexplored options and consequences in an atmosphere from which, despite the academic context, emotions were never entirely absent.
The three main themes addressed at the seminar were the future shape of US foreign policy, the role of oil, and the role of international law and international institutions - particularly the UN.
Prof Karl, who is a visiting scholar under the auspices of the EUI BP chair in transatlantic relations, suggested that within the US at present, the initiative had been seized by the right: defence expenditure was now guaranteed; the missile defence system was back on the agenda; there was a temporary demise of all domestic political opposition; and the country's economic problems could now all be safely blamed on the war.
In this context, it was ironic that so much of what had happened could be traced to what was now being described as a "blowback policy" - in this instance, the policy of supporting the mujaheddin, which had returned to plague those who had devised it.
Just as importantly, we were seeing a "paradigm shift" in US foreign policy in which the fight against communism was being replaced by the fight against terrorism in a way which would not only influence foreign policy itself, but also domestic spending priorities.
A black and white world was being created, in which military means would be used in an attempt to solve problems which had social and economic roots, and in which the repressive internal policies of America's allies would be overlooked in return for their aid.
One of the few comforting signs, in her opinion, was that although the administration was seizing the opportunity to attempt to roll back citizens' rights, Americans generally were not prepared to give a blank cheque to any attempt to limit political liberties.
Oil in general, and Saudi Arabia in particular, were the focus not only of Prof Karl but also of a number of other contributors, notably Prof Giacomo Luciano of the EUI's Robert Schuman Centre.
For years, he pointed out, the Saudi budget had a specific line for contributions to the Afghani mujaheddin: it was not there any longer, but this did not mean that Osama bin Laden was some lunatic character on the fringe of Saudi society: despite having been isolated from his family and deprived of his citizenship, he was an extremely wealthy man - and "it is an easy bet that there are still people who will answer his telephone calls if he comes to Saudi Arabia."
The problem for the Saudi rulers, he suggested, was that the isolation of bin Laden, which was an inevitable consequence of their links with the US, removed a key part of their political legitimacy, which was based not on any concept of the Saudi "people" or "state" but on a religious concept which went far beyond the borders of their own state,
For their part, they would have to find some way of justifying their support for the US if they were not to continue playing with fire; essentially bin Laden had grabbed the flag of Islamic legitimacy from the Saudi royal family, and it would be very difficult for them to take it back.
The wider effects of the crisis were underlined both by Prof Antonio Cassese - former chairman of the International Criminal Tribunal for the former Yugoslavia - and by Prof Pierre Dupuy of the EUI's law department. Each suggested, with different degrees of emphasis, that the apparent unanimity of the UN Security Council at its September 12th meeting masked a real danger to the role of international law.
Prof Cassese, in particular, suggested that the previously existing rules governing the use of force in legitimate self-defence by a nation which had been attacked were now being effectively "shattered".
This was because the rules envisaged a number of conditions that were plainly not applicable to the action the US proposed to take - even though it was being justified under the "self-defence" rules.
Under these rules, the reaction had to be directed against a state, not against individuals; it had to be immediate, not prepared over a long period of time; it had to end when the aggression had ceased; and it should not involve penetration into enemy territory.
The Security Council resolution of September 12th, he argued, represented a "huge departure" from this previously understood principle, and it was one which had huge practical consequences. All of this - including the suggested extra-judicial assassination of terrorists and the non-exclusion of the possible use of nuclear weapons - led to the possibility of all this violence "somehow degenerating into a third world war involving so many countries that the US may no longer have control over the use of force."
Among the few optimistic suggestions heard at the seminar was the idea that the delay which has been forced on the US for logistical reasons might also encourage a hesitation, at least, in its current, and long-conditioned unliteralism.
As Prof Karl pointed out wryly, George Bush senior regarded his coalition-building at the time of the war against Iraq as the major foreign policy triumph of his administration.
"This," she commented, "cannot have escaped his son. But even if it has, George Bush is still working, essentially, with the same foreign policy team his father had used."
Also on that side of the equation was Colin Powell, who combined a military man's belief that the only kind of force worth using was overwhelming force, with a belief in the importance of military multilateralism, and a respect for human life itself - and the loss of it - which had been forged in his personal experience in Vietnam.
On the other side of the equation was the defence intelligence agency team, not least the advisory trinity of James Schlesinger, Richard Perle and Henry Kissinger (a sequence of names which produced a sharp intake of breath among most of those present).
Among many ironies teased out at the seminar was a suggestion that the September 11th attack could more usefully be described as a "crime against humanity" rather than as an act of war, and could therefore be more properly dealt with by the proposed International Criminal Court.
The US, Prof Cassese pointed out, has been almost alone in resisting the establishment of an International Criminal Court, and had even argued that the competence of any such court should exclude terrorism, because the US believed that it could and should combat terrorism on its own - all this at a time when countries like Libya and Algeria were arguing that terrorism should be included in the brief of any such court.
"I'm at a loss to know", he commented quietly but trenchantly, "why they are the only country in the world to want their own forces to be brought before an American court. This is part of a mentality which is not acceptable to us in Europe."