Profile: The man who knew - Buddha: Peter Popham on the founder of the religion that isn't, inspiration for Bertolucci's new film

RICHARD GERE, Cindy Crawford, John Cleese, Harrison Ford and Danielle Mitterrand have struggled up rubble-strewn roads in the Himalayas to be initiated. Burglars, armed robbers and drug dealers have kicked their habits and locked themselves away on Holy Island for months on end to learn more. Now, Bernardo Bertolucci has completed his trilogy of films on oriental themes with Little Buddha. All have been seduced by the lure of Buddhism. What is the secret of its fascination?

Buddhism is the religion that isn't. St Peter's itself would not be disgraced by the splendour of Buddhism's rituals: the clouds of incense, the vast gilt images, the gorgeously robed priests, the ancient and magnificent buildings. Buddhism throngs with gods: dip into the ancient texts and they come at you in their thousands. Yet at the heart of Buddhism is not a god but a man: the young Indian prince, Siddartha, who sat, legs folded, under a tree until he saw, Buddhists believe, into the universe's empty heart. He was the first of many to do so.

Buddhism is both extremely complicated and extremely remote from Western culture, and the potential for misunderstanding is limitless. Is it about reincarnation? If there is no god, who are they chanting for? Why do they bow down before images? If none of these questions has easy answers, it is because Buddhist sects have proliferated; and if they contradict each other, Buddhists couldn't care less. 'There are 84,000 paths up the mountain,' they say, smiling calmly.

But all the sects find their touchstone in the experience of Siddartha under the peepul tree. This is also the climax of Bertolucci's film, which goes on release on Friday. The film tells in parallel the legendary tale of Siddartha and the search of lamas from Bhutan for the reincarnation of one of their number - a search that leads them to a small, blond-haired boy called Jesse in Seattle.

Siddartha was born about 2,600 years ago in a small town in the north of India, near the northern edge of the plain of the river Ganges. His father was the most important man in Kapilavastu, capital of the region dominated by the Shakya people; he was probably the elected head of the town's hereditary ruling class.

The young Siddartha was shielded from the brutal realities of existence; according to the legend, his father went to enormous trouble to prevent him from learning about suffering and death, fearing that if he did he would be tempted to abandon his inheritance and take up the life of a spiritual seeker. But to no avail. On successive trips out of the palace, Siddartha came across a very old man, a very sick man, a dead body about to be consumed on a funeral pyre, and finally a holy man. He had discovered dhukka, suffering. Soon afterwards he left the palace, determined to fathom the secrets of existence.

At first he fell in with ascetics. Holy men were already present in the sub-continent in great abundance, wandering through the woods in search of understanding. Siddartha learnt what he could from them, testing his flesh through fasting and other tormenting practices. (In the film, one of his self-mortifying companions sports a heavily weighted thong through his tongue.) But before he could kill himself with these torments, it occurred to Siddartha that there must be a better way. 'If you tighten the string too much it will snap,' he overheard a sitar teacher advising his pupil. 'If you leave it too loose it will not play.' Struck by the analogy to his own situation, he rolled down the river bank and into the river, where he slaked his thirst. His ascetic companions abandoned him in disgust. But Buddhism as the religion of commonsense - of the Middle Way - was on the way to being born.

Nursing himself back to modest health and vitality, Siddartha resumed his quest for understanding. Arriving at a place called Uruvela, the ancient name for what is now Bodh Gaya, he sat under a great peepul tree and folded his legs. He did not rise again until he had seen into the nature of things. It was, according to tradition, the work of a single night.

All religions involve prayer; some also enjoin believers to what is sometimes called 'oriental prayer' or meditation. But in no religion is the practice of meditation of such central significance as in Buddhism. Buddhists around the world bang drums, ring bells, light incense, prostrate themselves before images and chant sutras. None of these practices is considered optional or of slight importance. But take meditation - Siddartha under the peepul tree - away from Buddhism and you take the heart from it.

For Buddhists, meditation is not merely to calm the mind, improve the flow of alpha waves or prepare for a bout of yogic flying; it is a way of seeing, or of taking the first, squinting steps towards seeing what Siddartha saw; of seeing into 'the mystery of things' as penetratingly, in its way, as looking into an electron microscope.

At the moment of enlightenment, Siddartha understood that the self was an illusion. This was the most original of his insights, and has continued to resonate wherever Buddhism has travelled. According to the body of beliefs which we now know as Hinduism, the eternal self, or ego, or soul was connected to the eternal divine principle in the universe and transmigrated from rebirth to rebirth. 'The Buddha taught that there is no such thing as self,' writes Sherab Chodzin Kohn in his new book, The Awakened One, 'but only the illusion of a self. If a real self did exist, he explained, it would only be a cause of suffering, and if it were eternal it would be a cause of suffering that could never be removed.' But the self was illusory, and therefore suffering could cease. The enlightened being could escape from the cycle of life and death into the bliss of Nirvana.

Access to the truths of Buddhism can not be had through faith or reasoning; the only way to confirm its truth is to attain enlightenment. The words of Buddha are not there either to be believed or disbelieved, but as an incitement to follow his path, and an indication of the astounding experience that lies at the end of it. Because it is not a code revealed once and for all on some mountain-top, but rather an experience waiting to happen, it has been expressed in many different ways down the centuries. Each is a refraction of the same realisation through the sensibility of the person meditating.

One of the most celebrated expressions is 'the Heart Sutra', the description of the vision of emptiness experienced by one of Buddha's disciples who tells another: 'Form is emptiness, emptiness also is form. Emptiness is no other than form, form is no other than emptiness.' The sutra continues in a rhapsody of negation: imagine this as it is chanted in temples around the Buddhist world, in a brisk, ecstatic monotone, accompanied by staccato beats on a wooden drum:

'. . . In emptiness there is no form, no feeling . . . no eye, no ear, no nose, no tongue, no body, no mind . . . no smell, no taste, no touch . . . no ignorance, no end of ignorance . . . no old age and death, no end of old age and death; no suffering, no origin of suffering, no cessation of suffering, no path, no wisdom, no attainment and no non-attainment . . .'

Siddartha became known as Shakyamuni Buddha, 'the seer of the Shakya, The Awakened One', and began spreading the word. He returned home - he had been away seven years - and recruited his father, wife and son to the new teaching. In contrast to the problems encountered half a millennium later by Jesus, Buddha's teaching was hailed and adopted wherever he went, and he lived a long and happy life, dying after a short illness at the age of 80.

In the West, Buddhism is usually seen as an individual's search for enlightenment; but in the East it had from the outset a strong social and political dimension. At the heart of this was the sangha, the corps of monks. But while a Christian monastery is normally remote from society, the sangha was an urban institution, ideally functioning as a moral compass for society. The insights of Buddhism might be hard both to attain and to understand, but their moral ramifications were much easier to pin down: in essence, an attitude of compassion and non-violence to all things. About two-and-a-half centuries after Buddha's death, the Emperor Ashoka, who inherited a kingdom which occupied most of the subcontinent, became the first ruler to attempt to govern along Buddhist lines: trying to coexist peacefully with neighbouring states, setting up hospitals for people and for animals, building shady rest stops for travellers and so on. In all these endeavours, the sangha was there to guide him.

While Ashoka's was arguably the most successful attempt to infuse affairs of state with Buddhist wisdom, there have been many others, from the Buddhist state set up in Sri Lanka in Ashoka's time to the similar venture of Japan's Prince Shotoku 800 years later. When monks in Vietnam set themselves alight during the Vietnam war, when monks in Burma defied the military junta, they were acting in accordance with an ancient tradition of social responsibility. Not that immersion in Buddhist ideas has saved Sri Lanka or Burma from frequent civil bloodletting.

Today more than 200 million people in Asia depend on Buddhism for some aspect of their spiritual lives. The type and degree of observance varies widely: in Japan most people only encounter Buddhist priests during funeral services, but in Thailand or Burma Buddhist holy days are widely celebrated, and millions of young men take months or years off from their regular lives to become monks.

The sangha, in its broadest sense the Buddhist church, has shattered into a thousand fragments since Buddha's time. Sects range from the immensely learned and ceremonious in Tibet to the simple chanting of the Nichiren sects in Japan, and the comedy, poetry and austerity of Zen. In this easily tolerated diversity, Buddhists manifest a serene confidence in the fundamental truths. 'Why believe,' one teacher used to say teasingly to Christians tempted to dabble in Buddhism, 'when you can know?'