That they did willingly, and so, through three intermediaries, science came to the Arabs. There was a heathen Syrian source with its centre at Harran, of which we know comparatively little. There was a Christian Syrian source working from the multitudinous monasteries scattered over the country. There was a Persian source by which natural science, and medicine especially, were passed on. Already in the fifth century A.D. an academy of medicine and philosophy had been founded at Gondeshapur in Khuzistan. One of the directors of this institution was summoned, in 148, to prescribe for al-Mansur, and from that time on it furnished court physicians to the Abbasids. On these three paths, then, Aristotle and Plato, Euclid and Ptolemy, Galen and Hippocrates reached the Muslim peoples. [Sidenote: GOLDEN AGE OF MUSLIM SCIENCE] The first hundred years of the Abbasid Khalifate was the golden age of Muslim science, the period of growth and development for the People of Muhammad fairly as a whole. Intellectual life did not cease with the close of that period, but the Khalifate ceased to aid in carrying the torch. Thereafter, learning was protected and fostered by individual rulers here and there, and individual investigators and scholars still went on their own quiet paths. But free intellectual life among the people was checked, and such learning as still generally flourished fell more and more between fixed bounds. Scholasticism, with its formal methods and systems, its subtle deductions and endless ramifications of proof and counter-proof, drew away attention from the facts of nature. The oriental brain studied itself and its own workings to the point of dizziness, and then turned and clung fast to the certainties of revelation. Under this spell heresy and orthodoxy proved alike sterile.