But they remain outsiders, heretics, residing far beyond the city gates, because they speak their own private languages. Their ideas make no sense to us; their words are nonsense.

Of course, any radically new idea, any new way of looking at the world, at our place within it, particularly when presented as a new faith, attracts resistance. Having to think again, having to think at all, is a painful process for many people. And, of course, any threat to the status quo, to the power of the priesthood, is viewed with suspicion.

For proof, look at the three great organised religions. At the moment of their founding, all introduced heresies, the idea of doubt, into their world-view. Judaism contains the story of the tree of knowledge. The fruit introduced the capacity to see good and evil, to doubt. Christianity is founded on St Peter, the "rock", who was also a supreme doubter.

And, according to some Islamic historians, the Prophet Mohammed allegedly received blasphemous verses form the angel Gabriel. This story has a long tradition and is mentioned by at least three respected early thinkers - Ibn Ishaq, Ibn Sa'd and Tabari.

The new faiths went against the grain. They attracted hostility. But because their message contained the truth, the revelations at the core of all the world's great religions, they were able to win over new converts. "Heretics" turned into prophets.

In Amin Maalouf's The Gardens of Light, the story of Mani, the charismatic third century mystic, provides an oblique comment on how ideas enter into the world and the reception, the incredulity, the scorn, that they often receive.

Painter, doctor and prophet, Mani was born in Mesopotamia, in modern-day Iraq. He advocated a "Gospel of Light" - a complex religious system derived from elements of early Christian beliefs, ancient Persian Zoroastrianism, Buddhism and paganism.

The Magi, the high priests of Zoroastrianism, felt threatened by the power that Mani exercised over his disciples and had him imprisoned and eventually killed. However, his ideas spread - a search for harmony between men, nature and the deity; an account of the struggle between the two eternal conflicting principles of light and darkness.

Between the third and 14th centuries Manichaeism became a major world religion, with communities in places as far apart as France, China and India. Then, as Christianity and Islam swept all before them, it became labeled a heresy. Its believers were persecuted; its sacred texts were lost. The faith disappeared.

The winner of France's most prestigious literary prize, the Prix Goncourt, for The Rock of Tanios in 1993, Maalouf was born in Lebanon and now lives in France. He writes in a deceptively simple style.

Perhaps it echoes the plainness of the great revealed texts. Or that of plainsong, the early Christian's contemplative songs in which voices sang the same tune but without harmony.

In its starkness, Maalouf's prose acts like a draught of cleansing water - mimicking Mani's effect on the people around him, no doubt. Its clearness rests in stark contrast to the confusion of today's styles.

But if his style shouts out the importance of coherence, Maalouf's message remains one of toleration. In many ways, Manichaesim was a pick 'n' mix religion, taking freely from whatever lay at hand. The clash of ideas, Maalouf suggests, breeds new ideas, is a creative act.

The Gardens of Light is far removed from the New Age mysticism that floats around today. It contains no fireworks, no showy veneer of cleverness. Narrating its lost history, the book weaves the current mood of restlessness, the feeling that orthodox ways of understanding the world may be moribund, into something seemingly safe. Only seemingly. As in anything truly revolutionary, here the reader provides the spark.