There is a tale for our troubled times about a man on a desert island, who keeps goats, builds a shelter and finally discovers footprints in the sand. But it is not called Robinson Crusoe. It was written by a wise old Muslim from Andalusia and is the third most translated text from Arabic after the Koran and the Arabian Nights.
It is called Hayy ibn Yaqzan or "Alive, Son of Awake", and it was a sensation among intellectuals in Daniel Defoe's day. As has happened before during times of tension between Islam and the west, it is again emerging from the shadows and that is a matter for celebration, whether in New York or Baghdad.
The book's author, Ibn Tufayl, was vizier to the 12th-century Caliph Abu Yaqub, but his restless mind took him into speculative fields more often frequented by revolutionaries. In an age when faith was essentially compulsory, he stood for reason and the noble Hellenic tradition of putting everything to the test.
His creation, Hayy - an onomatopoeic word with a lovely lift on the second "y" - is reason incarnate; in seven sequences of seven years, he puzzles out everything from astronomy to zoology. Charmingly, Tufayl has him baffled at not having horns like the island's gazelles, or struggling with his skirt of leaves, which keep withering and falling off. But all the time, the philosopher is in the background, saying "Don't take it on trust. Think."
Appropriately for a teacher, the vizier is known to history not for Hayy, but for a lesson in Marrakech with tremendous consequences for European thought. In the winter of 1169, he and the Caliph were joined by a fellow Andalusian, Ibn Rushd, for whom the two older men had a task; to Rushd's alarm, the Commander of the Faithful began asking him forbidden philosophical questions.
Rushd stuttered aghast over whether the world was created in a single divine act or - potentially a capital offence to claim - complexities like eternal matter might have been involved. But the Caliph and Tufayl launched into the issue with gusto, moaning that they were too old to tackle such riddles of "the Ancients", Aristotle and Plato.
So began the great work of Averroes (Rushd's westernised name), which led to Europe's first Renaissance as his commentaries on the Greeks, translated from Arabic, returned the philosophers' lost works to the west. He is Dante's "Famed Commentator" in the Divine Comedy and the only brown face in Raphael's School of Athens.
But Tufayl? No. Three poems and the 70 pages of Hayy are all that survive of his work and that was not enough for Parnassus. He caused his own small medieval stir, especially among Jewish thinkers prominent in the great translation "factory" run in Toledo by Archbishop Raymond. The light that shone from Tufayl illuminates Maimonides' Guide of the Perplexed. But then it passed into obscurity, until an Oxford don went shopping in Aleppo in 1653.
The souk must have loved Edward Pococke, professor of Arabic and a famously genial enthusiast for the Muslim world, who came home burdened with souvenirs. Planting a Syrian cedar cone at his Berkshire vicarage and a Syrian fig in Christchurch, he handed his son, also Edward and another Arabic scholar, an age-mottled folio of neat calligraphy. It was Hayy ibn Yaqzan.
Now in the Bodleian, the manuscript was copied in Alexandria in 1303 by an unknown scribe, probably Jewish, as the script is annotated in Hebrew. Pococke Junior's translation was published in 1671 and there was an immediate stir. The Enlightenment was in full swing and the book, sub-titled "The Self-Taught Philosopher", addressed the notion of a tabula rasa, an innocent mind developing through its own powers, which was absorbing John Locke. Locke refers eagerly to a meeting in London to discuss "this novelty" and three English translations followed. Spinoza pressed successfully for a Dutch translation, Leibnitz enthused about the book, which went into German twice, and Pococke's agent wrote from Paris: "I delivered a copy to the Sorbonne for which they were very thankful, being much delighted with it."
Then came Defoe, for whom the story married marvellously with the memoir of Alexander Selkirk, the real-life Crusoe. From Robinson's early capture by Moors to the seldom-read sequel "Robinson Crusoe's Vision of the Angelic World", Tufayl's footprints mark the great classic.
Hayy is a different character from Crusoe but in a way that adds to his story's potency today. If the book was ultimately a lexicon for Using Your Head, its attraction for the practical, restlessly innovative west might not be shared by the more contemplative east. But in its highest manifestation, Hayy's reason leads him to personal awareness of God (or what Tufayl calls, with a philosopher's precision, the Necessarily Existent Being.) This is its great appeal for readers in the Muslim world where - although eclipsed as regularly as in the west - it is a hallowed Sufi text.
Tufayl's motives are lost to us; but there is no doubt about his commitment to reason even if - perhaps as a veil to hide behind from heretic-hunters - he accepts that it is not for everyone. When Hayy leaves his island with Absal, his equivalent of Friday, to proselytise to the wider world, his preaching is a fiasco. His incomprehension that anyone could chop off a man's hands for theft threatens social order. The two "ineffectual angels", as one translation nicely describes them, return to the island of gazelles and content themselves with personal salvation until "life's one certainty came to them".
The book is also an undoubted rebuke to anyone who debates fundamental issues with excessive conviction that they are right. Hayy's island life endlessly teaches him tolerance; he uses only what he needs for survival. He harvests or kills at times of the year when species can reproduce. He lives and lets live.
This philosophy chimes with a vital age-group today. In an online forum run by Stanford university, a young American recalls a bedtime story of a desert-island girl raised by dolphins to be tolerant and kind. Another writes: "I guess Tufayl wants to show parallels among people even if they haven't been exposed to other cultures." A third, archetypally American, comments: "Isn't that special?"
The same thread runs through the latest English version of Hayy, a long overdue adaptation of the story for children conceived as a National Curriculum course by the Ismaili Aga Khan Foundation. The title has changed yet again, but the meaning remains Tufayl's: It is called The Boy Who Learned to Think for Himself.
· "Child on an Island" is the Sunday Feature on Radio 3 tomorrow (5.45-6.30pm), presented by Martin Wainwright, northern editor of the Guardian.