The atheist is an embattled soul. If we think of those proud to proselytise their atheism today - Christopher Hitchens, Richard Dawkins - we find that they are above all polemicists, wearily prolonging a juvenile rebellion. Popes and fundamentalists are their sustenance. And vice versa.Without the quarrel, both parties might be obliged to move on.

My own atheist period lasted the time it took to escape an evangelical family. My father, an Anglican clergyman, had become involved in the charismatic movement. There were exorcisms and a delirium of tongues and prophesies. In the event, it was such a relief to escape into the world of cold reason that the loss of eternal life seemed a small price to pay. For three decades, I have avoided all futile discussion of the existence of God and the place of man in the universe. The only religious ceremonies I attend are weddings and funerals. Last year, when, over the coffin of a friend's son, the priest announced that the boy was gazing down on us from paradise, it was evident that not a single mourner could take comfort from these ill-chosen words. The old formulas no longer suit.

But life is long and so much of it lies outside the highly verbal environment in which atheists and believers assert their divisive identities. There is also the silence when walking through fields in twilight, or sitting beside a sleeping child; there is the dismay as ageing parents decline; the mad pleasures of physical intimacy; sickness, déjà vu, dreams. Comes the moment when you are no longer afraid to turn and look at all that lies beyond the metalled rails of career and consumerism. In summer 2008, I amazed myself by signing up for a ten-day Vipassana meditation retreat with the ageing American teacher John Coleman.

I went for health reasons. So I told myself. For some years, an inexplicable condition had walled me up in chronic stomach pains and urinary embarrassments. The medical profession prospected operations to bladder, prostate and intestines, prescribed powerful medications and batteries of intrusive tests. Which turned up nothing. Eventually, and very gradually, I found relief in breathing exercises and shiatsu. It was the shiatsu practitioner who pointed out that the breathing exercises were in fact a form of meditation. Not a word I cared for. "You should go to a Vipassana retreat," he said. When I objected that this smacked of Buddhism, he laughed. "Just go for the physical benefits."

I looked it up on the internet: "Vipassana means seeing things as they really are. It is the process of self-purification by self-observation. It is a universal remedy for universal problems." "Universal" and "remedy", I thought, were words that, when put together, could only epitomise wishful thinking. Purification, on the other hand, was a concept I couldn't begin to understand and hence a goal I could hardly desire. As for seeing things as they are, I knew that this meditation was done with the eyes closed.

The retreat was in a monastery-turned-conference centre. After registration, one had an hour to chat before taking a vow of silence. The 70-strong group was a mixed bag: men and women, young and old, New Age and no, posh and rough. As we drank tea together, I found this person was credulous, another sceptical, this boy yearning for mystical experience, that man frightened of losing his mind. When a girl expressed doubts about her ability to sit cross-legged for 12 hours a day, a haggard man in his forties remarked that "the position" was not the problem. It seemed there was a problem, but it was not "the position".

What then? Not money. These retreats cost nothing. At most, one pays modestly for food and board. In return, you are expected to rise at 4am for a 4.30am start, to accept simple vegetarian food and only two meals a day, to keep silent throughout - in short, to live a monkish life. And to learn this meditation method.

For the first three and a half days, you are instructed to do nothing but sit cross-legged and focus on the breath as it crosses the upper lip entering and leaving the nose. When the sitting position is painful, you are to observe it without thinking of it as your pain; when wayward thoughts disturb your concentration, you are to take note but not attribute them to yourself.

By the evening of day two, I had had enough. Feet, ankles, knees, thighs and hips were weld­ed together in a scorching pyre from which my curved trunk rose like the torso of some broken martyr. Round this carnage, thoughts flitted and circled like bats in smoke.

It would be impossible to convey how many thoughts arose, or how systematically they blocked all my attempts to focus on my breathing. Had my mobile phone not been removed on arrival, I would have called my shiatsu man and told him what I thought about the "physical benefits".

Yet I didn't leave. I was as much enthralled as appalled. Sitting still, in silence, I found that an astonishing exposure to my thought pro­cesses was going on. How interminably words dragged one away from the here and now of sensation! How tiresomely self-regarding and self-dramatising the thoughts they formed were. In compensation, there was a growing sense of community with those sitting quietly around me hour after hour, some in deep trouble, as I was, fidgeting and sighing and rearranging their mats and cushions, others seraphically still, beautifully erect and fresh. I wanted to be like them.

On the afternoon of day four, Vipassana proper begins. Having learned to focus and free itself from words, the mind detaches from the breath to move slowly through the body from head to toe and back, exploring every sensation, every absence of sensation.

I had just discovered that when one did manage to fuse mind and flesh in the touch of the breath on the lip, the sense of well-being was immediate, the muscles relaxed, the sitting position became not only possible, but pleasant. Moving away from this to explore the body was like stepping from a cool balcony into a burning house. I would never have imagined that the body could provide so much essentially meaningless pain. Nor that I would have been willing to put up with it.

Coleman became important now. His son­orous voice clicked in and out of the silence to guide us round our bodies with a calm and deeply reassuring charisma. "Let go," he commanded when we arrived at a point of tension. "Just let go." Towards day seven, I began to get, very fleetingly, a sense of the whole body flowing together in a state of serene, liquid energy. I had stopped waiting for each hour to end.

But the real surprise of the retreat came with the last meditation before the silence was ended - the "metta bhavana", or meditation of loving kindness. Outside the meditation hall, moving around the grounds, I had noticed as the days went by that the natural world was intensely present to me in a way that was unusual and moving. The absence of input was allowing for a simple sense of pleasure in being here.

When the old man began the metta bhavana, I found an unexpected generosity welling up in me. There is no point in denying it: Tim Parks is a misanthropist, interminably critical of his fellow man. Yet here I was, feeling something suspiciously like love, or St Paul's charity. It rose from depths I knew nothing of. And to tap in to it, I hadn't had to surrender my reason to any belief structure. Just by putting the chatter aside and reinhabiting my body, I had experienced a big shift of feeling. My shiatsu man, I realised now, must have known all along, being a holist, that one can't just take the physical benefits without undergoing a change of heart.

When the atheists take religion to task for its absurd beliefs or for the damage it has done, we have no choice but to agree. They could hardly have an easier target. Yet the intimations that lie behind religions remain and are not going to go away because someone has written a book denying God. They are part of our reality. How we respond to those feelings, individually and collectively, will very largely define the kind of community we become. One can only hope that they do not crystallise in divisive creeds.

“Teach Us To Sit Still" by Tim Parks is published by Harvill Secker (£12.99)