In the service of the Kurdish-Turkish Sultan Salah al-Din ibn Ayyub (Saladin صلاح الدين يوسف بن أيوب ), the nemesis of Richard the Lionheart during the second crusade, there was published a definitive treatise by Khayyām on algebra in which he classified algebraic equations up to the third degree and showed how geometric solutions to the equations could be obtained.
Ironically, the source of Khayyām’s most enduring legacy is neither his mathematics nor his science but rather his poetry. The Rubaiyat, a translation, or recomposition, published initially in 1859 by the British poet Edward Fitzgerald, presents his work in a series of melancholic ruminations concerning the irreversibility of fate and the fleeting nature of life.
One explanation of the decline of science in Islāmic civilization, which began in the late fifteenth century, is the general fatalism that pervaded Islāmic culture, as revealed in the melancholia and pathos of Khayyām’s quatrains describing life continuing among the ruins of ancient grandeur.
Another explanation is the emergence in twelfth century Baghdad of an intellectual movement spearheaded by the fundamentalist al-Ghazali, which favoured faith and dogma over reason and direct evidence.