ataclysms not only cast shadows over human victims but also shake the foundations of intellectual life: wars can shift the direction of scholarship; genocide can upend the presumptions of sociology. The destruction of the World Trade Center and the attack on the Pentagon may have similar effects, challenging the intellectual and ethical perspectives of two sets of ideas: postmodernism (affectionately known as pomo) and postcolonialism (which might be called poco). These ideas, which have affected political debate and university scholarship, are now being subject to a shock that may lead in two directions: on one hand to a more intense commitment, and on the other ?I hope ?to a more intense rejection.

In general postmodernists challenge assertions that truth and ethical judgment have any objective validity. Postcolonial theorists, who focus on cultures that have experienced Western imperialism, agree in part, suggesting that the seemingly universalist principles of the West are ideological constructs. Many have also implied that one culture, particularly the West, cannot reliably condemn another, that a form of relativism must rule.

But such assertions seem peculiar when trying to account for the recent attack. This destruction seems to cry out for a transcendent ethical perspective. And even mild relativism seems troubling in contrast. It focuses on the symmetries between violations. But differences, say, between democracies and absolutist societies or between types of armed conflict are essential now. Debate over these kinds of interpretations are now heating up. So it might be worth examining some hypotheses of poco and pomo.

First of all there are some significant differences between the two ideologies. Pomo is partly an attempt to question the fundamental philosophical and political premises of the West. It argues that many of the concepts we take for granted ?including truth, morality and objectivity ?are culturally "constructed." And some scholars generally agree, including the historian of science Thomas S. Kuhn, who argued that science could not lay claim to universal truths, and the pragmatist philosopher Richard Rorty, who has challenged objective notions of truth.

Poco, though, has a more specific ambition, analyzing the effects of colonialism on what used to be called the third world, knottily interpreting how postcolonial societies absorb and contend with the West. But within the poco ideology, Western claims of objectivity are still put into question. In "The Postcolonial Studies Reader" (1995, Routledge), for example, the governing perspective, the editors explain, is opposition to the West's "myth of universality," which is little more than a "strategy of imperial control." One contributor writes: "Postcolonialism is regarded as the need, in nations or groups which have been victims of imperialism, to achieve an identity uncontaminated by universalist or Eurocentric concepts and images."

In the Sept. 17 issue of The Nation ?published just before the attack on the World Trade Center ?Edward Said, one of postcolonialism's founding theorists, also points out that unlike radical pomo advocates, he accepts universal principles like "human rights." Still, he refers to "ideological confections": ideas like "the clash of civilizations" that, coincidentally, were invoked by many European and American leaders in condemning the terrorist attack. Such "false universals," Mr. Said says, are used to legitimize "corporate profit-taking and political power." Similar arguments have become commonplace in worldwide protests against "globalization."

Follow this logic to its most extreme conclusions, and the rejections of universal values and ideals leave little room for unqualified condemnations of a terrorist attack, particularly one against the West. Such an attack, however inexcusable, can be seen as a horrifying airing of a legitimate cultural grievance. Military responses can seem no different. And so the conflict becomes a series of symmetrical confrontations, as is often asserted about battles in Israel.

Poco, though, goes further. For while affirming most of the pomo rejection of ideals and universals, poco establishes its own universal: Western imperialism becomes a variety of Original Sin. The implication is that any act against the West by a postcolonial power can be seen as a reaction to an act by the West.

These ideas simplify interpretation tremendously. Western imperial behavior is seen as the fundamental cause of terrorism, the evil of the former leading to the evil of the latter, thus creating a rough symmetry in which differences are minimized.

In last week's issue of The Nation, for example, one writer, after condemning the "indescribable evil" of the attack, says, "This is not really the war of democracy versus terror that the world will be asked to believe." The terrorist attacks, he suggests, were a result of injustices caused by the West. Another writer says that "our own government, through much of the past 50 years, has been the world's leading `rogue state,' " having been responsible for killing "literally hundreds of thousands if not millions, of innocents."

A column from The Guardian, the British newspaper, calls terror attacks "counterproductive acts of outrage" against Western injustice. Similar sentiments have been expressed about Israel, which is considered a proxy for the United States. A commentator for the BBC said that supposed Israeli violation of international law was a cause, if not the main cause, of terrorism.

These attitudes are not a traditional expression of left-wing politics. The anti-Western virulence is too strong, and the weakening of judgment against terrorism too prevalent. Symmetries are strained for; one culture (the West) is seen as no more virtuous ?indeed far less so ?than another, leading to comments that sound eerily similar to some extreme justifications offered in the Arab world.

Of course the errors and apparent venality of the West must be considered in examining radical Islamic terrorism. But the intellectual focus on a single and continuing Original Sin creates a skewed perspective.

As the historian Bernard Lewis has shown, the origins of what he calls Islamic hatred of the West are complicated: a history of struggles going back almost 14 centuries, the fear of modernity felt by "right wing" theocratic fundamentalists, the countries' widespread poverty conjoined with demagogic clerics and wealthy rulers. Terrorist rage is also directed against Arab regimes in which secular life reigns over the religious realm (as in Egypt and Jordan).

Christopher Hitchens, while attacking the West in the current issue of The Nation, writes: "Does anyone suppose that an Israeli withdrawal from Gaza would have forestalled the slaughter in Manhattan? It would take a moral cretin to suggest anything of the sort; the cadres of the new jihad make it very apparent that their quarrel is with Judaism and secularism on principle, not with (or not just with) Zionism."

For now though these considerations are subsumed by poco ideology, spiced by pomo sentiments. While condemning the recent attacks, they establish near symmetries between the outrage of both sides, and they eliminate perspectives that might reveal fundamental cultural differences (like those affirmed, unambiguously, by the attackers). The great ironic twist is that the values latent in pomo and poco ?an insistence that differing perspectives be accounted for and that the other be comprehended ?are consequences of the very ideas of the Western Enlightenment ?reason and universality ?that they work to undo.

One can only hope that finally, as the ramifications sinks in, as it becomes clear how close the attack came to undermining the political, military and financial authority of the United States, the Western relativism of pomo and the obsessive focus of poco will be widely seen as ethically perverse. Rigidly applied, they require a form of guilty passivity in the face of ruthless and unyielding opposition.