Workers, Socrates once remarked, make bad friends and bad citizens. Socrates, of course, lived in classical Athens where free men (and philosophers) had plenty of time for dining and democracy: the slaves did all the work. Today we are free, but there's no time any more. If we have work, we are slaves to it.

The dangers of overwork and the effects on health, marriage and family life have been widely debated. In the Sunday Review today, Annabel Ferriman reveals the latest thinking on what has been called "the disease of the Nineties". As summarised by CharlesHandy, the business theorist, the trend among employers is to employ half the people, drive them twice as hard and get three times the productivity. If they burn out, so what? There are plenty more queueing up for jobs. Handy warns that the 67-hour weekis around the corner: our working life may be dropping from 47 to 30 years, but we will still be putting in the same 100,000 life-time hours.

But it is not just the quantity of work that has changed; the quality has changed, too. And that may have effects that we have hardly begun to consider. Is it possible that work, in its modern form, makes us not just tired and stressed but robs us of creative vigour as well? Is it affecting the quality of our thoughts?

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The nature of work is changing in two ways. First, people who actually make things are becoming rarer. Second, everyone will be doing much more "symbolic analysis".

"Symbolic analysts", according to Robert Reich, the US Labour Secretary and former Harvard academic, are people who "solve, identify and broker problems by manipulating symbols". They spend much of their time sitting at computer terminals but rarely comeinto contact with the people at the other end of the network. They will be the emperors of the new service and information economy. They are the highly trained technocrats and white-collar staff, the architects, the managers, the market-makers.

Remember Sherman McCoy, the self-styled "master of the universe" who was the hero of Tom Wolfe's Bonfire of the Vanities? By Reich's calculations, symbolic analysts already account for 20 per cent of American workers, against 8 per cent in the 1950s.

But though the future looks rosy for the symbolic analysts (more than any other group, they have benefited from the polarisation of wealth over the past 15 years) they seem lukewarm about their prospects. We give labels to the psychological toll of the new world of work (overwork, stress, "burnout") and we put estimates on the cost (£8bn, 80 million working days lost each year), but we don't really understand it. What we do know is that the 67-hour week is doing something unpleasant to our sense of wellbeing - not least to what used to be called our souls.

Westerners have a peculiar attitude to work: they believe (or once believed) that it has a moral purpose. Outside Europe and North America, most people do not share this view. Nor did Europeans before the age of Protestantism. They did less work and believed hardly at all in its ennobling nature. As authorities such as Professor Marshall Sahlins, author of Stone Age Economics, have shown, even the much-maligned hunter-gatherer was a creature of leisure - the bushman had a 15-hour working week.

The work ethic, which linked grace and salvation to good works, was the psychological engine of capitalism. But with Christianity in retreat, and its transcendental reward system largely discredited, all that remains of the work ethic is the after-taste.We have the compulsion without the high moral purpose. Hence the "joyless striving" associated with heart attacks.

Robert Bly, guru of the embryonic "men's liberation" movement, says that some of the most passionate talk in men's groups comes from those "who feel that they have walked up a blind alley in their jobs: the rationality is too dry, or the job has gone dead for them, or it leaves them no time to be with their family, or it is stupid and dishonourable. The emphasis falls on the soul damage that much contemporary work causes."

We have learnt to expect a lot from work. The work ethic taught us to look for fulfilment. We would also like it to be fun. In pure economic terms, we need to be creative: ideas are the currency of the information age, the key to competitive success. On all these counts, the future looks bleak.

Symbolic analysis - the manipulation of facts, figures, concepts - is a supremely intellectual process. It is what psychologists call a "left-brain" function. Experiments suggest that the two cerebral hemispheres govern distinct areas of human function: the left brain is abstract, rational, organising, the right brain intuitive, intimate and mystical. The idea is echoed in the yin and yang of Taoism, in Edward de Bono's opposition of lateral and vertical thinking, in Arthur Koestler's oppositi on of theyogi and the commissar. What they all speak of is the need for psychological balance and wholeness, and the risks when these are disrupted.

The changes in work threaten to disrupt the balance fundamentally. In the space of half a generation, millions of us have been swept up into office blocks and placed in front of fax machines and computer screens where we analyse and manipulate symbols endlessly, in conditions close to sensory deprivation - controlled, artificial, rigorously excluding anything not conducive to work. We process greater volumes of information at higher speeds over longer periods. Quantitatively, we are much more efficient;qualitatively, we are stunted.

Technology has made communication faster and easier but eliminated the need for human contact. Information transfers once involved travel, meeting people, going to the library, talking to your bank manager. Superficially, it seems that the same information is being conveyed; in reality, one exchange is much richer than the other. A hand-drawn piece of graphic art is creative in a way that a computer-aided diagram is not. A story read over a telephone to a child at bedtime by a working mother is a different story from the one she would read at home.

Yet in the new punitive regime of business life, employers may be as much the victims as employees. The regime reinforces what de Bono has called Catch 24, which states that "in order for a person to reach the most senior position in an organisation he (or she) should have kept hidden - or be without - exactly those talents that will be needed when he (or she) gets there". These, says de Bono, are the lateral-thinking or right-brain talents needed for creativity. According to recent research from the Sundridge Park management centre, many businesses face "slow death" because, in the process of terrorising their workers into submission, they are filtering out diversity and creativity.

Creativity requires space and time, for reflection and contemplation. Before Archimedes ran through the streets of Syracuse crying "Eureka", he was lying in his bath. Koestler calls this "reculer pour mieux sauter" (pulling back before you jump). Margaret Boden, professor of psychology and philosophy at Sussex University, points out that creative ideas seem to come when a person "appears to be thinking about something else, or not really thinking at all".

Genuine creativity also has close affinities to play. The controlling ego of the left brain lets go, the doors of perception are cleansed, the mind doodles and experiments, finding unexpected connections. By and large such life-enhancing flow experiences, where the right brain emerges from incarceration, do not happen in offices. They do often occur out of doors, in "real" environments, with plenty of space and no pressure. There is a growing body of research that demonstrates this.

Masters of the universe notwithstanding, we are all symbolic analysts now, from the data processors in telephone insurance companies to the teachers disappearing under a tide of administration: the difference is merely in degree. But a 67-hour week of symbolic analysis and not much else looks like a dangerous mixture. What happens when the work stops and we are thrown back on to our own resources? Suppose we don't have any because we have been too busy working? Seeing where the solutions lie - more people-friendly working practices, more not less regulation - doesn't make them any easier to achieve. But it does help to recognise the awful truth: work really can make you stupid.