One of the first and most significant indications of the new orientation of Muslim thought was the extensive production of Arabic translations of works dealing with philosophical and scientific subjects, with the result that eighty years after the fall of the `Umayyads the Arabic speaking world possessed Arabic translations of the greater part of the works of Aristotle, of the leading neo-Platonic commentators, of some of the works of Plato, of the greater part of the works of Galen, and portions of other medical writers and their commentators, as well as of other Greek scientific works and of various Indian and Persian writings. This period of activity in translating falls into two stages, the first from the accession of the Abbasids to the accession of al-Ma´mun (A.H. 132-198), when a large amount of work was done by various independent translators, largely Christians, Jews, and recent converts from non-Islamic religions; the second under al-Ma´mun and his immediate successors, when the work of translation mainly centered in the academy newly founded at Baghdad, and a consistent effort was made to render the material necessary for philosophical and scientific research available for the Arabic speaking student. The earlier translation work is especially associated with _`Abdullah b. al-Muqaffa`_, a native of Fars and originally a Zoroastrian, who made his profession of faith before a brother of Muhammad b. `Ali, the father of as-Saffah, and became his secretary. Presuming on his employer’s protection he ventured to make derisive and impertinent remarks to Arab dignitaries and especially to Sufyan, the governor of Basra, whom he used to salute with a lewd jest against his mother’s chastity. It seems that men of Arab birth who held political office under the early `Abbasids often had to put up with such insults from the ex-serfs. After an unsuccessful attempt at revolt by another of the Khalif’s uncles Ibn al-Muqaffa` was directed to prepare a draft letter of pardon to be presented to the Khalif al-Mansur, who succeeded his brother as-Saffah, for his official seal, but he drew up the letter in such terms as to arouse the Khalif’s indignation; amongst other things the letter said, “if at any time the Commander of the Faithful act perfidiously towards his uncle `Abdullah b. `Ali, his wives shall be divorced from him, his horses shall be confiscated for the service of God (in war), his slaves shall become free, and the Muslims loosed from their allegiance to him.” The Khalif enquired who had prepared this letter and on being informed directed Sufyan to put him to death. Pleased thus to gratify his personal rancour the governor of Basra executed Ibn al-Muqaffa` with great cruelty, though the details differ in different accounts, in A.H. 142 or 143.