The translators of Arabic mathematical and astronomical works during the twelfth century prepared the way for an event of the first magnitude in the intellectual history of the Middle Ages—the reintroduction of Aristotelian learning into the West.[424] It would lead us far beyond the bounds of this study to try to discuss the immense influence of Aristotelianism on the development of European philosophy and theology in and after the thirteenth century. Something of the geographical content of Aristotle’s writings on physics and natural science, however, was indicated in Chapter I, and it was during the closing years of the twelfth and the beginning of the thirteenth centuries that these works began to gain a hold on European thought. Their influence at this time was for the most part exerted through roundabout channels: probably in some cases through Latin translations of Arabic translations from the original Greek; unquestionably in others through Latin translations of Arabic translations of Syriac translations from the original Greek; and in still others through Latin translations of Arabic commentaries on Aristotle or of works inspired by his writings. The desire or ability to tap the sources of Aristotelian lore by direct recourse to Greek texts themselves was exceptional before the middle of the thirteenth century. The precise date when the Occident became acquainted with the _Physics_ and _De caelo_ is a matter of some doubt. It is likely that Avicenna’s version of these two books had been converted into Latin at Toledo before the middle of the twelfth century by Dominicus Gondisalvi,[425] who worked there under the patronage of Archbishop Raymond, but the extent to which these early translations influenced European science is a subject of controversy. It has been suggested by Duhem that Latin translations of Aristotle were known to the scholars of the Chartres school, Theodoric, Gilbert de la Porrée, and William of Conches, passages in whose works certainly reveal some familiarity with Peripatetic theories.[426] On the other hand, there are no actual citations of Aristotle which would enable us to prove that the passages in question show first-hand knowledge of the books of the Stagirite.[427] The fact that much Peripatetic thought had been brought to the West through the writers of the late Roman and earlier Christian periods often makes it difficult, in the absence of actual citations, to distinguish between what had been learned from these earlier sources and what was contemporaneously derived from the Moslems. _Gerard of Cremona_ We are on much firmer ground when we turn to the work of Gerard of Cremona,[428] for we know as a fact that before his death in 1187 this indefatigable translator had put into Latin, of the works of Aristotle of geographical interest, the first three books of the _Meteorology_,[429] the _Physics_, the _De caelo et mundo_,[430] and the _De generatione et corruptione_.[431]