'It's good to be different' might be the motto of our times. The celebration of difference, respect for pluralism, avowal of identity politics – these are regarded as the hallmarks of a progressive, antiracist outlook. Belief in pluralism and the multicultural society is so much woven into the fabric of our lives that we rarely stand back to question some of its assumptions. As the American academic, and former critic of pluralism, Nathan Glazer puts it in the title of a recent book, We Are All Multiculturalists Now.

I want to question this easy assumption that pluralism is self-evidently good. I want to show, rather, that the notion of pluralism is both logically flawed and politically dangerous, and that creation of a 'multicultural' society has been at the expense of a more progressive one.

Proponents of multiculturalism usually put forward two kinds of arguments in its favour. First, they claim that multiculturalism is the only means of ensuring a tolerant and democratic polity in a world in which there are deep-seated conflicts between cultures embodying different values. This argument is often linked to the claim that the attempt to establish universal norms inevitably leads to racism and tyranny. Second, they suggest that human beings have a basic, almost biological, need for cultural attachments. This need can only be satisfied, they argue, by publicly validating and protecting different cultures. Both arguments are, I believe, deeply flawed.

The case for 'value pluralism' has probably been best put by the late philosopher Isaiah Berlin. "Life may be seen through many windows," he wrote, "none of them necessarily clear or opaque, less or more distorting than any of the others." For Berlin, there was no such thing as a universal truth, only a variety of conflicting truths. Different peoples and cultures had different values, beliefs and truths, each of which may be regarded as valid. Many of these values and truths were incommensurate, by which Berlin meant that not only are they incompatible, but they were incomparable, because there was no common language we could use to compare the one with the other. As the philosopher John Gray has put it, "There is no impartial or universal viewpoint from which the claims of all particular cultures can be rationally assessed. Any standpoint we adopt is that of a particular form of life and the historic practices that constitute it." Given the incommensurability of cultural values, pluralism, Berlin argued, was the best defence against tyranny and against ideologies, such as racism, which treated some human beings as less equal than others.

This argument for pluralism is, as many have pointed out, logically flawed. If it is true that "any standpoint we adopt is that of a particular form of life and the historic practices that constitute it", then this must apply to pluralism too. A pluralist, in other words, can never claim that plural society is better, since, according his own argument, "There is no impartial or universal viewpoint from which the claims of all particular cultures can be rationally assessed". Once you dispense with the idea of universal norms, then no argument can possess anything more than, at best, local validity.

Many multiculturalists argue not simply that cultural values are incommensurate, but also that different cultures should be treated with equal respect. The American scholar Iris Young, for instance, writes that "groups cannot be socially equal unless their specific experience, culture and social contributions are publicly affirmed and recognised."

The demand for equal recognition is, however, at odds with the claim that cultures are incommensurate. To treat different cultures with equal respect (indeed to treat them with any kind of respect at all) we have to be able to compare one with the other. If values are incommensurate, such comparisons are simply not possible. The principle of difference cannot provide any standards that oblige us to respect the 'difference' of others. At best, it invites our indifference to the fate of the Other. At worst it licenses us to hate and abuse those who are different. Why, after all, should we not abuse and hate them? On what basis can they demand our respect or we demand theirs? It is very difficult to support respect for difference without appealing to some universalistic principles of equality or social justice. And it is the possibility of establishing just such universalistic principles that has been undermined by the embrace of a pluralistic outlook.

Equality requires a common yardstick, or measure of judgement, not a plurality of meanings. As the philosopher Richard Rorty observes, the embrace of diversity and the desire for equality are not easily compatible. For Rorty, those whom he calls 'Enlightenment liberals' face a seemingly irresolvable dilemma in their pursuit of both equality and diversity:

Their liberalism forces them to call any doubts about human equality a result of irrational bias. Yet their connoisseurship [of diversity] forces them to realise that most of the globe's inhabitants do not believe in equality, that such a belief is a Western eccentricity. Since they think it would be shockingly ethnocentric to say "So what? We Western liberals do believe in it, and so much the better for us", they are stuck.

Rorty himself, a self-avowed 'postmodern bourgeois liberal', solves the problem by arguing that 'equality' is good for 'us' but not necessarily for 'them'. We can see here how the argument for incommensurability leads not to equal respect for, but to an indifference to, all other cultures.

Equality arises from fact that humans are political creatures and possess a capacity for culture. But the fact that all humans possess a capacity for culture does not mean that all cultures are equal. "We know one of the realest experiences in cultural life', the art critic Robert Hughes has observed, "is that of inequalities between books and musical performances and paintings and other works of art".

Much the same could be said about all cultural and political forms. Some ideas, some technologies, some political systems are better than others. And some societies and some cultures are better than others: more just, more free, more enlightened, and more conducive to human progress. Indeed the very idea of equality is historically specific: the product of the Enlightenment and the political and intellectual revolutions that it unleashed.

The idea of the equality of cultures (as opposed to the equality of human beings) denies one of the critical features of human life and human history: our capacity for social, moral and technological progress. What distinguishes humans from other creatures is the capacity for innovation and transformation, for making ideas and artefacts that are not simply different but also often better, than those of a previous generation or another culture. It is no coincidence that the modern world has been shaped by the ideas and technologies that have emerged from the Renaissance and Enlightenment. The scientific method, democratic politics, the concept of universal values – these are palpably better concepts than those that existed previously. Not because Europeans are a superior people, but because many of the ideas and philosophies that came out of the European Renaissance and Enlightenment are superior.

To argue this today is, of course, to invite the charge of 'Eurocentrism', or even racism. This simply demonstrates the irrationality of contemporary notions of 'racism' and 'antiracism'. Those who actually fought Western imperialism over the past two centuries recognised that their struggles were rooted in the Enlightenment tradition. "I denounce European colonialist scholarship," wrote CLR James, the West Indian writer and political revolutionary. "But I respect the learning and the profound discoveries of Western civilisation."

Frantz Fanon, one of the great voices of postwar third world nationalism, similarly argued that the problem was not Enlightenment philosophy but the failure of Europeans to follow through its emancipatory logic. "All the elements of a solution to the great problems of humanity have, at different times, existed in European thought," he argued. "But Europeans have not carried out in practice the mission that fell to them."

Western liberals have often been shocked by the extent to which anti-colonial movements adopted what they considered to be tainted ideas. The concepts of universalism and unilinear evolutionism, the French anthropologist Claude Levi-Strauss observed, found "unexpected support from peoples who desire nothing more than to share in the benefits of industrialisation; peoples who prefer to look upon themselves as temporarily backward than permanently different." Elsewhere he noted ruefully that the doctrine of cultural relativism "was challenged by the very people for whose moral benefit the anthropologists had established it in the first place."

Multiculturalists have turned their back on universalist conceptions not because such conceptions are racist but because they have given up on the possibility of economic and social change. We live in an age in which there is considerable disillusionment with politics as an agency of change, and in which possibilities of social transformation seem to have receded. What is important about human beings, many have come to believe, is not their political capacity but their cultural attachments. Such pessimism has led multiculturalists to conflate the idea of humans as culture-bearing creatures with the idea that humans have to bear a particular culture.

Clearly no human can live outside of culture. But to say this is not to say they have to live inside a particular one. To view humans as culture-bearing is to view them as social beings, and hence as transformative beings. It suggests that humans have the capacity for change, for progress, and for the creation of universal moral and political forms through reason and dialogue.

To view humans as having to bear specific cultures is, on the contrary, to deny such a capacity for transformation. It suggests that every human being is so shaped by a particular culture that to change or undermine that culture would be to undermine the very dignity of that individual. It suggests that the biological fact of, say, Bangladeshi ancestry somehow make a human being incapable of living well except as a participant of Bangladeshi culture. The idea of culture once connoted all that freed humans from the blind weight of tradition, has now, in the hands of multiculturalists, become identified with that very burden.

Multiculturalism is the product of political defeat. The end of the Cold War, the collapse of the left, the defeat of most liberation movements in the third world and the demise of social movements in the West, have all transformed political consciousness. The quest for equality has increasingly been abandoned in favour of the claim to a diverse society. Campaigning for equality means challenging accepted practices, being willing to march against the grain, to believe in the possibility of social transformation. Conversely, celebrating differences between peoples allows us to accept society as it is – it says little more than "We live in a diverse world, enjoy it". As the American writer Nancy Fraser has put it, "The remedy required to redress injustice will be cultural recognition, as opposed to political-economic redistribution." Indeed so deeply attached are multiculturalists to the idea of cultural, as opposed to economic or political justice, that David Bromwich is led to wonder whether intellectuals today would oppose economic slavery if it lacked any racial or cultural dimension.

Not only is the demand for 'recognition' the product of political pessimism, it is also a means of implementing deeply authoritarian policies. Consider, for instance, Tariq Madood's distinction between what he calls the "equality of individualism" and the "equality encompassing public ethnicity: equality as not having to hide or apologise for one's origins, family or community, but requiring others to show respect for them, and adapt public attitudes and arrangements so that the heritage they represent is encouraged rather than contemptuously expect them to wither away."

Why should I, as an atheist, be expected to show respect for Christian, Islamic or Jewish cultures whose views and arguments I often find reactionary and often despicable? Why should public arrangements be adapted to fit in with the backward, misogynistic homophobic claims that religions make? What is wrong with me wishing such cultures to "wither away"? And how, given that I do view these and many other cultures with contempt, am I supposed to provide them with respect, without disrespecting my own views? Only, the philosopher Brian Barry suggests "with a great deal of encouragement from the Politically Correct Thought Police".

The thought police are already at work. On more than one occasion over the past decade I have been refused permission by both newspaper and radio editors to quote Salman Rushdie's The Satanic Verses because it was considered to cause too much 'offence'. The McPherson inquiry into Stephen Lawrence argued that even racist comments made in the privacy of the home should be made a criminal offence. Thankfully, this suggestion has so far been ignored politically. Many multiculturalists, however, wish to go further still, demanding that all private thought and feelings be subject to political scrutiny. Iris Young welcomes what she calls "the continuing effort to politicise vast areas of institutional, social and cultural life". Politics, she suggests, "concerns all aspects of institutional organisation, public action, social practices and habits, and cultural meanings". "The process of politicising habits, feelings and expressions of fantasy and desire" can, Young believes; "foster a cultural revolution."

Culture, faith, lifestyle, feelings – these are all aspects of our private lives and should be of no concern to the state or other public authorities. Multiculturalist policies inevitably bring to mind Orwell's description in Nineteen Eighty-Four – "A Party member lives from birth to death under the eye of the Thought Police... His friendships, his relaxations, his behaviour towards his wife and children, the expression on his face when he is alone, the words he mutters in his sleep, even the characteristic movements of his body are all jealously scrutinised."

The irony of multiculturalism is that, as a political process, it undermines what is valuable about cultural diversity. Diversity is important, not in and of itself, but because it allows us to expand our horizons, to compare and contrast different values, beliefs and lifestyles, and make judgements upon them. In other words, because it allows us to engage in political dialogue and debate that can help create more universal values and beliefs, and a collective language of citizenship. But it is precisely such dialogue and debate, and the making of such judgements, that contemporary multiculturalism attempts to suppress in the name of 'tolerance' and 'respect'.

A truly plural society would be one in which citizens have full freedom to pursue their different values or practices in private, while in the public sphere all citizens would be treated as political equals whatever the differences in their private lives. Today, however, pluralism has come to mean the very opposite. The right to practise a particular religion, speak a particular language, follow a particular cultural practice is seen as a public good rather than a private freedom. Different interest groups demand to have their 'differences' institutionalised in the public sphere. And to enforce such a vision we have to call in the Thought Police.

Multiculturalism is an authoritarian, anti-human outlook. True political progress requires not recognition but action, not respect but questioning, not the invocation of the Thought Police but the forging of common bonds and collective struggles.