THIS is a story that analyses the beginning and searches for an end, if, indeed, an end will ever come. It is a story of science versus religion; brilliance versus disability; theory versus empiricism; public persona versus private reality. The life of Stephen Hawking, the most famous living scientist, is a life of conflict.

This week the conflict came again. Professor Hawking's latest theory on what happened in the first trillion trillion trillionth of a second of time - that minuscule period which so

preoccupies the minds of cosmologists - and its consequences for the universe has been criticised by one of the world's most respected physicists, the Russian Andrei Linde, before it has even been published.

That two eminent physicists are embroiled in an intellectual fight should come as no surprise: from the Babylonians onwards, scientists have been possessed with both a great talent for bickering and tongues sharper than the knives of Arbroath fish wives. Yet the squabble has predictably filled newspaper columns: science is a new religion and its blind adherents are always upset when its high priests argue.

The point over which the two squabble is both fundamental and esoteric; hugely interesting yet beyond the understanding of most of us. Professor Hawking postulates that the universe began at a fixed point and it will continue forever, there will never be an end. Andrei Linde says that Hawking, and his co-author Neil Turok, are fundamentally wrong: there is no point to Hawking and Turok's search for a beginning or an end since universes such as ours come into existence regularly.

Hawking and Turok's new theory answers the question which was at the centre of A Brief History of Time: the universe is currently expanding but the forces which power this expansion are in opposition to the gravitation power of the matter within it, so will the universe expand forever or will it eventually collapse in upon itself, an enormous blackhole?

Professor Hawking has plumped for the former, but Linde claims his density measurements - fundamental to the calculations - are incorrect and, anyway, the question is irrelevant, Hawking and Turok are barking up the wrong tree.

It is a tribute to the talent of Hawking, both as a writer and a scientist, that he is capable of interesting the public in such cerebral questions. Few scientists - Einstein, Newton - have commanded the public's attention in the way that Professor Stephen William Hawking has done. The slumped figure in a wheelchair has become as much a part of scientific iconography as the periodic table itself.

He was born on January 8, 1942, exactly three centuries to the day after the death of Galileo. His Scottish mother, Isobel, and his medical-researcher father, Frank, furnished him with an unconventional childhood. He grew up in St Albans, a town that is quintessentially middle England in attitude if not location, but the family's idiosyncrasies - their car was a black cab and holidays were taken in a gipsy caravan - helped to break the tedium.

At school, life was difficult for Hawking. His intelligence, feeble physique, and the lisp he inherited from his father singled him out; he was the typical bullied swot. Classmates remember him as a bit of a loner, a young man strangely more interested in jazz than pop, problem-solving rather than chatting.

Predictably, Hawking won a scholarship to Oxford, but, while he was a promising student, he is not remembered as a brilliant one. It was only after a great deal of work in his final term that Hawking won his First. His degree, however, was sufficiently good for him to win a PhD place at Cambridge; and it was there that the brilliance, and the tragedy, began.

In his first term, Hawking became clumsy and his lisp turned to a slur: these were the first stages of motor neurone disease.

''The realisation that I had an incurable disease that was likely to kill me in a few years was a shock,'' he has said. But he has lived far longer than any doctor would have predicted: motor neurone disease normally kills within two or three years, but Hawking has lived with the condition for more than 35. He has survived longer than any other sufferer.

It was at Cambridge that he met his first wife, a language student named Jane Wilde, at a New Year's Eve party. Hawking had just been diagnosed with motor neurone disease and he swayed through periods of suicidal depression. Of their romance he said: ''It gave me something to live for.''

The couple married in 1965, around the time of the publication of Hawking's brilliant PhD thesis. His illness obviously made marriage a very big step for both, but Wilde has said that she found purpose in her life through the idea of looking after Hawking.

In the coming years Hawking's condition became debilitating in almost inverse proportion to the blossoming of his academic brilliance. By the early seventies his speech was so slurred that few could understand him, but, all the while, his papers were becoming more and more profound, and it was during this period that he attained one of his greatest academic achievements.

Hawking succeeded in marrying relativity and quantum mechanics, two branches of physics that were previously irreconcilable. (Einstein himself refused to accept the validity of quantum mechanics, famously stating ''God does not play dice'' whenever he was questioned on the subject.)

His reliance on Jane became more and more absolute, and the fact that the pair had, by then, three children, made life for Wilde extremely difficult.

His daughter Jane has described just how difficult.

''After getting the children ready for school, she would lift my father out of bed and into his chair. She would then wash him, feed him, and get him off to work . . . We always ate supper together as a family. Each mouthful for my father had to be chopped into minute pieces and fed to him, which took hours. As he always had his mouth full, I developed a repertoire of jokes and patter to while away the eternity at the table. As a special treat, my father could sometimes be persuaded to waggle one of his ears.''

It is this image of the trapped genius, a man troubled only by great thoughts, not earthly concerns, that most people hold of Hawking. It is one that the media have been happy to hype - Time magazine famously wrote, ''helpless in his wheelchair his mind seemed to soar'' on the publication of ABHoT - but it is wholly inaccurate. Hawking's genius is irrelevant to his disability. His daughter, Lucy, says: ''For as long as I can remember my father has maintained a resolute disbelief in his own disability.'' Hawking himself says: ''I don't think motor neurone disease can be an advantage to anyone.'' And

the breakdown of his marriage shows that he is a man with desires and concerns placed most resolutely on the terra firma.

In 1989, Hawking announced that he was leaving his wife Jane to live with his nurse Elaine Mason. It was the year after the publication of ABHoT, and his friend, Professor David Schramm of the Chigago University, blames the book's success for the marriage breakdown.

''If you ask me, it was his transition from academic to world celebrity and superstar that led in the end to him and Jane going in separate directions,'' he says.

There were many other pressures on the marriage - such as Hawking's resolute atheism - but Hawking's decision to leave Jane for the wife of the man who had given him his voice - Elaine Mason was married to David, the Cambridge engineer who designed the synthesiser Hawking uses to communicate to the outside world - was undoubtedly selfish.

His wife Jane spoke bitterly of the break-up; Hawking, perhaps alone among cosmologists, made tabloid headlines; even the broadsheets chose to ponder the nature and extent, if any, of his and Jane's sexual relationship. The brouhaha proved what many had suspected: Hawking, in the public consciousness at least, was now more celebrity than scientist.

Stephen Hawking is undoubtedly a brilliant scientist, but whether he is a truly great scientist is a matter of academic debate. He has proved that blackholes are not black and that time can be measured using imaginary numbers - numbers which involve the square root of minus one - but it is unlikely that he will ever win a Nobel Prize. His science eschews test-tubes and tripod stands, Bunsens and burettes, for pure theory; these theories will never be proved or disproved empirically, at least not in our lifetimes, so the Nobel is likely to elude him.

As a writer and communicator on science, Hawking is undoubtedly gifted. Yet ABHoT, by far his best-selling book, is a very difficult read and his communicative talents are, perhaps, overshadowed by others such as Dawkins and Feynman. So what then has made Stephen Hawking such a cultural icon?

Perhaps it is the image of martyred genius. Perhaps it is the metallic voice, as recognisable as that of Marlon Brando or Jimmy Stewart. Perhaps it is the BT adverts and the talent for self-promotion. Perhaps it is his search for the ultimate solution: the Grand Unifying Theory. Whatever the answer, only his celebrity is without doubt.

At the end of ABHoT Stephen Hawking said that he sought to understand ''the mind of God''; the rest of us must seek only to understand the mind of Hawking.