We have seen that the contemporaries of Abailard knew none but Aristotle's logical works, and these only in part and in Latin translations. So far nothing had interfered with the development of thought along "purely Western, purely Latin, purely Christian" lines. Churchmen who did not disapprove of dialectic altogether, had accepted and used Aristotle so far as they understood what they had of his works. Heretics there had been, but hitherto none had questioned the authority of the Bible or the Church. Meanwhile in the east a completer knowledge of Aristotle's works had been communicated by the Nestorian Christians to their Mohammedan masters. Greek books were translated into Arabic, and Arabian philosophy, already monotheistic, became permeated with Aristotelian ideas. Moreover, the union of philosophical and medical studies among the Arabs caused them to attach a special value to Aristotle's treatises on natural science. In Spain the Arabs handed on their knowledge of Aristotle to the Jews, and it was from the Jews of Andalusia, Marseilles, and Montpellier that the works of the Greek philosopher and his Arabian commentators became known in the west. [Sidenote: Revival in the west.] By the middle of the twelfth century the chief of these works--texts, paraphrases, commentaries--had, at the instance of Raymond, Archbishop of Toledo, been rendered into Latin by Archdeacon Dominic Gondisalvi, assisted by a band of translators. But the translations of Aristotle's own works were not from the original Greek, but from the Arabic, which laid stress upon the most anti-Christian side of Aristotle's thought, such as the eternity of the world and the denial of immortality. The result was an outbreak of heretical speculation along pantheistic lines. Swift steps were taken: the heretics were hunted down, and in 1209 the Council of Paris forbade the study of Aristotle's own works or those of his commentators which dealt with natural philosophy; while in 1215 the statutes of the University renewed the prohibition. But such prohibition did not include any of the logical works; and in 1231 a bull of Gregory IX only excepted any of Aristotle's works until they had been examined and purged of all heresy. Finally, in 1254, a statute of the University actually prescribed nearly all the works of Aristotle, including even the most suspected, as text-books for the lectures. Meanwhile fresh translations were made from the Arabic by Michael Scot and others at the instance of Frederick II, so that by 1225 the whole body of his works was to be found in Latin form. Further still, the Latin conquest of Constantinople in 1204 had brought back to the west a knowledge of a large part of Aristotle's writings in their original form. Translations were now made into Latin straight from the Greek; and Thomas Aquinas, seconded by Pope Urban IV, took especial pains to encourage such scholarship. [Sidenote: The later Scholasticism.]