It was a bit of a surprise to learn that among the many deaths that were counted in the thick, unbreathable dustclouds rolling up Manhattan from the Trade Center was that of the figure of irony. No less a journal of our time than Time itself announced "One good thing could come from this horror: it could spell the end of the age of irony."

Irony of course is an instrument much deployed by the smartypants of the intelligentsia. Not only untrustable by good plain folk, it is liable, if not kept thoroughly down, to infect them with irresolution, ambiguity in all its types, let alone the downright cowardice which stops people doing what needs to be done.

Indeed, Ronald Reagan's sometime education secretary, William Bennett, not only picked a fight with irony, he attributed it, bless us all, to the 'postmodernists'. In Why We Fight: moral clarity and the war on terrorism, he sentenced the whole lot of them to a detention in which they would undergo "a vast relearning [...] the reinstatement of a thorough and honest study of our history, undistorted by the lens of political correctness and pseudosophisticated relativism."

'Moral clarity' was simultaneously much invoked by the President himself as burnishing the breastplate of his righteousness, while he sallied out to face and slice up his elusive enemy, the roaring lion of Kabul, or Baghdad, or Damascus, or wherever the bastard may be, if only he would stand still long enough to be shot at.

In point of fact, things weren't all that ironic amongst the postmodernist intelligentsia. In the too-prompt and frequently egregious factory noticeboard published by the London Review of Books two weeks after September 11, Tariq Ali, alphabetic first in this archangelic choir, accused politicians of "turning blind eyes to the Middle East", which is simply fatuous (and has been since 1916), and contemptuously accused an undifferentiated 'West' of regarding Saudi Arabia as "simply a source of oil", which is merely mauvaise foi: for the foreseeable future, no oil means no civilisation, whatever barbarity it entails, a truth equally applicable to the LRB, Ramallah or Camp David.

After Tariq Ali, Mary Beard was, infamously, coarse enough to write, "when the shock has faded [pretty quickly for her, it seemed], more hard-headed reaction set in. This wasn't just the feeling that, however tactfully you dress it up [not at all, in her case], the United States had it coming."

Last in this selection from an unappetising motley, the delirious pentecostal of postmodernism, Fredric Jameson, approached things armed to the teeth with inverted commas, and ineffably announced, "I have been reluctant to comment on the recent 'event' because the event in question, as history, is incomplete and one can even say that it has not yet fully happened."

The postmodern intelligentsia should be reproached not for their irony, still less for 'pseudosophisticated relativism', but rather for self-righteousness, self-referentiality and an impregnable sanctimony only made to tremble by the danger of speaking with strong and spontaneous feeling about circumstances of such deliberate horribleness.

The failure was one of thought, thought charged to the utmost with the actuality of experience and the feelings inseparable from living it.

Who, for example, could take seriously someone who talks like this?

"This, strictly speaking, is de(con)structive pedagogy. Like all good teaching in the humanities, it is hopeful and interminable. It presupposes and looks forward to a future anterior of achieved solidarity, and thus nurses 'the present'. In the strictest sense, then, (para)logical: morpho-genetic (giving rise to new ways of reading, writing, teaching in the strongest sense) without terminal teleological innovation. Its 'present' is a field of value-coding ..."

These are the author's italics, brackets, inverted commas, and the author's absurdly pretentious diction. Without them she would have been able to articulate more clearly that the teaching she wants to see, forceful as it should be, is never finished and always optimistic of renewing a common culture by way of intelligent study in the present and moral affirmation of the future. Those commonplaces may be pious but are none the worse for it. Our author, however, is not on a mission of clarity. She is a self-styled 'diasporic postcolonial', a high-caste Hindu, "a feminist who is an old-fashioned Marxist"; she is also a wonderfully high-paid American academic star of lectern, stage and screen; she charges fifteen thousand bucks for a public performance; she was first translator into English of the mischievously difficult father of Deconstruction and Postmodernism, Jacques Derrida of the exquisite dove-grey suiting; she is called Gayatri Spivak.

For my purposes, poor thing, she serves first as comic pedant, polysyllabic, wholly unironic, earnestly bien-pensant, blind to her own privileges. She leads, with a due reluctant modesty, a commando of proselytising admirers. They teach the truism that literature in English is now worldwide, much of it written by people once under the yoke of Empire ('subaltern' in the argot); that this means that the old canon of great books has fallen into ruins; that moral and literary authority are alike dissolved in the hot tides of globalisation. This is anti-foundationalism, where the foundations were the hard facts of objective judgement and absolute truth.

Spivak and her disciples would do well, given these beliefs, to disavow her 'old-fashioned Marxism'. What the old man himself called 'the real foundations' of economic production readily assumed the kind of authority she appears to eschew and, when it came to politics, would win its moral and political arguments with a carefully placed bullet in the back of the neck.

It is a reflex of postmodernism that it affirms an allegiance with the Left. While I yield to no woman in my detestation of an economic system which has indeed, as Marx said it would, "fetishised the commodity", and which so indifferently thrives on distant cruelty and street starvation, the sentimental attachment of dissenters to a damned and damnable totalitarianism only makes them more popularly ridiculous.

I bumped into a textbook of cultural studies the other day which (as the phrase goes) 'called for' a grand myth of the subject and of the society, one in which the devout student would be cleansed of cultural stereotyping; immune to the charm of 'closure' in narrative (translator's note: 'happy endings'); inclusive of all those stigmatised by the deadly trinity of race, class and gender; interrogative of all texts while alive to the density of context; bricklayer to the building of "an ironic political myth faithful to feminism, socialism and materialism."

Hard to be less ironic than that, hard to be damn sillier. But with such inebriated ambitions around – and though they would never put it so innocently, these are nearly enough the beliefs of most of the soft postmodernists – it may be the time to retrieve one or two more ancient values from the dustbin of history. In the face of abstraction and theory, it would be a relief to reach for the old Platonic trusties, beauty, truth and goodness.

Of course, no one can doubt that relativism really has permeated our moral and aesthetic sensibilities, and no bad thing either. Relativism also has its truth and goodness. It is a consequence of the spread of folk-anthropology and of democratic feeling as well. Its central premise – that actions should be evaluated in context – would hold for any serious morality.

Relativists are quite right to say that the individualising of values – the inevitable product of any globalisation not designed to transform politics into management-by-moral-technology – is no more than a common recognition of the impossible variety of historical experience and human credulity.

In the clamorous and bloodstained souk of the world, however, people still go unrepentantly on looking out for good lives, trusting to tell the truth about their own, pausing on the off-chance of seeing something or somebody of such beauty as to fill their hearts with gladness and restore to them the hope of a better world.

In political argument, the only universal currency of moral exchange is an arid doctrine of rights - needful enough, but by definition the justification for bickering at best and murder much of the time. The exigency of politics is its collapsing absolutely everything in front of power-without-value (old-fashioned Marxists are especially staring-eyed in this way).

But breathing in culture is not the same thing as practising politics. Culture carries in the structure of its so-much-contested meaning open reference to the best that is in human beings, the beautiful things they can make, the good lives they may live. Without an imaginable beauty, there would be no ideal in terms of which to strive for a more actually beautiful world. The most damnable thing about so much modern art has been that it taught its audience to anticipate not fulfilment but disturbance, not a vision of the best but a reminder of the worst.

No doubt the art of the last century supped full of horrors. But its greatest masters - TS Eliot, Wallace Stevens, Henri Matisse, VS Naipaul - justify Emerson's wonderful dictum, that "in every work of genius we recognise our own rejected thoughts." Those thoughts, we might add, turn on the question of what is best in us, and what the world can do to bring it out.

Beauty, Plato said first and Iris Murdoch reminded us, is a good we love quite naturally. Beauty, without any effort of our own, brings with it the intensely pleasurable and delightful sense of certainty. It may not last (though most people remain pretty certain of the beauty of this Mozart concerto or that Turner painting). But it fires us to seek the certainties which are true, and these, when found, are good in themselves and good for us.

No doubt the gap between your taste in beauty and mine is often raucously comic though always interestingly comparative. But however shy-making all this is to our devout postmodernists, no one can quite get along without the things of beauty and, as Keats said, the joy they bring for ever. Each of us is filled with a happy relief to be dealing with a good person, and submits to her authority. And the virtue of truth is that it shall make you free.

Fred Inglis is Professor Emeritus of Cultural Studies, University of Sheffield. His People's Witness: the journalist in modern politics is published by Yale. Culture will appear in Spring 2004