My old philosophy professor said that universities shouldn't have to justify themselves to society; instead, society should have to justify itself to universities. But since no one takes any notice of philosophers, it is universities, not society, that remain on trial. And unless they can prove they are useful they may face the ultimate penalty, closure.

Who, though, defines what is useful? Why, business of course. We all know that. And what is useful, says the businessman or woman, is what benefits the economy. So as long as universities help to promote productivity, either in the form of research or training, their existence will be tolerated.

Now, there are many in the sector - and I count myself among them - who deplore this philistine approach to intellectual life. We desperately need strong arguments to counter the corrosive effects of brutal utilitarianism that are not just felt in universities but in the culture at large. The idea that we should pursue knowledge for its own sake, though, is not one of them.

For a start there is the problem of terminology. Knowledge and information are often used interchangeably. We are told we live in the information age and work in the knowledge economy, but the two terms are not the same. Historically, knowledge - which often had a religious dimension - was the preserve of the few who sought to protect it from the many. The rise of science, the spread of democracy and especially the development of technology have undermined the traditional mystique that surrounded it. Knowledge has been transformed into information, which, in theory at least, is freely available to all.

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Another difference is that knowledge was part of a world view. An understanding of the Old and New Testaments gave a comprehensive account of the beginning and end of the world. But the ever-expanding nature of information means that it cannot become the basis of a philosophy of life.

It is too vast, too diffuse ever to form a consistent and coherent narrative of human experience. We may lose the security of knowledge for the insecurity of information, but by knowing more we gain a greater control over our lives.

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Even if we ignore the linguistic confusion, the idea of "knowledge for its own sake" is simply untenable. At the most basic level it flies in the face of what we know about living organisms - that their existence depends on the transmission, translation and processing of information.

In evolutionary terms, the notion of knowledge for its own sake is a luxury no creature can afford. The same is true if we move from biology to culture, despite the best efforts of figures such as Cardinal Newman to prove otherwise.

It was he who coined the expression knowledge for its own sake in The Idea of a University (1854), but he traced the principle back to Cicero who, he claims, distinctly "separates the pursuit of Knowledge from those ulterior objects to which certainly it can be made to conduce". But it is hard to see how Newman reaches this conclusion when Cicero states that it is "excellent" to excel in the quest for knowledge while to err, to be ignorant or to be deceived "is both an evil and a disgrace".

This is not knowledge for its own sake, this is knowledge as a moral good. Moreover, "the knowledge of what is hidden or is wonderful (is) a condition of our happiness". Knowledge does not just make us virtuous, it brings us contentment.

Solomon, the most likely author of the Old Testament book Ecclesiastes, begs to differ. For him increase of knowledge brings increase of sorrow. But while he and Cicero may disagree about the ends of knowledge, they are in no doubt that it has an effect. And they are right: from Adam biting the apple to Rutherford splitting the atom, knowledge has consequences. Some of which may even be good.

Try giving an example of useless knowledge. You can't. Because what is useless to you may not be so to someone else. Knowing that the streaked bombardier beetle is the UK's rarest insect is exciting to an entomologist but probably not to a classicist. The value of knowledge depends, like so much in life, on context. Even if you do find an example of useless knowledge, the mere fact that it is an example means that it serves a purpose, that of illustrating the point you wish to make, and is therefore no longer useless.

There is no fact so trivial that it may not prove useful. Knowing that Nuuk is the capital of Greenland could take you up to the next level of prize money on Who Wants to be a Millionaire? But even if you never have the opportunity to sit opposite Chris Tarrant, you still benefit from reading all those encyclopaedias. Recent research has shown that keeping mentally active not only enhances brain functions, it also reduces the risk of developing neurodegenerative diseases.

Imagine if universities were based on the principle of knowledge for its own sake. It would mean they would have to cut many of their courses. How would they survive if they ceased to teach accounting and finance, architecture and construction, dentistry, engineering, environmental studies, fine art, law, medicine, marine technology, modern languages, psychology and counselling, public relations, town planning and so on? In effect, the doctrine of knowledge for its own sake is an abdication of a university's responsibility to the wider community.

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And since the removal of so many courses would reduce the number of students going to university, that same doctrine is also potentially elitist. And what would those still able to go to university do there? There would be no teaching because as soon as you pass on knowledge it is not for its own sake but for those who receive it. But what would students do with it if they, too, believed that knowledge should only be pursued "for its own sake"?

They certainly wouldn't expect to be assessed on what they had learnt. Such thinking would eventually lead to the disappearance of degrees. Then the young would be able to spend more time on MySpace and that would be the end of civilisation as we know it. Which, come to think about it, may be no bad thing.

Defending universities by appealing to the doctrine of knowledge for its own sake is like giving your opponent a loaded gun and promising to stand still while he shoots you. In effect you concede the argument because you accept that universities deal solely with knowledge, not critique. The only difference is in your attitude to knowledge: you say don't use it, but your opponent says let's cure cancer. There's no contest really, is there?

We need something better than the doctrine of knowledge for its own sake if we are going to argue that universities do more than serve the economy. First, we should be clear about what we mean by knowledge, if that is indeed the right term. How is it constituted, how interpreted, how assessed?

Then again, knowledge has a different meaning in the sciences from what it has in the humanities. This, incidentally, is another reason why the doctrine of knowledge for its own sake fails; it takes no account of the diverse nature of different disciplines.

Secondly, we should admit that knowledge, at least in the sciences, does indeed have a use even though that use may not be immediately apparent. Biochemist Paul Nurse discovered a gene for cell division while watching yeast for a number of years.

It turned out that his discovery, which earned him a knighthood and a Nobel prize, led to a breakthrough in understanding how cancer cells grew. A good example of the need for the blue-skies research that the Government is so reluctant to fund.

What about the humanities, though? We must challenge the research model that has been imposed on us. We are not scientists; we do not aspire to objectivity, nor do we proceed by hypothesis and experiment. Instead, our primary interest lies in the exploration of values. Arnold's phrase "the free play of ideas" could serve as our motto.

We may not help to eliminate disease or develop alternative forms of power, but with the aid of great thinkers past and present we ask important questions about ourselves, the world and the form of society in which we live. Naturally the corporate culture does not encourage our efforts because they reveal, all too clearly, the poverty of its economic conception of life; a conception summed up in a recent advertisement for a philosophy lecturer with "special reference to business ethics".

The advert - which my old professor would have called a contradiction in terms - shows how the humanities are being colonised. We are being forced to "live in the chinks". But we can do some good there, providing we drop our obsession with knowledge for its own sake. How about a bit of good old-fashioned ideology critique instead?

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