The Syrian Christians, who were the first to adopt Greek teachings, seem never to have gone beyond the mathematical and medical works of the Greeks and the logic of Aristotle. The Arabs began where their Syrian teachers ended, and went beyond them. The Mutakallimun were indebted to the Stoics,[226] the Pure Brethren to the Neo-Platonists; and it was only gradually that Aristotle became the sole master not merely in logic, which he always had been, but also in physics, metaphysics and psychology. Alfarabi, Avicenna and Averroes represent so many steps in the Aristotelization of Arabic philosophy. Christian mediæval thought, which was really a continuation of the Patristic period, likewise began with Eriugena in the ninth century under Platonic and Neo-Platonic influences. Of Aristotle the logic alone was known, and that too only in small part. Here also progress was due to the increase of Aristotelian knowledge; though in this case it was not gradual as with the Arabs before them, but sudden. In the latter part of the twelfth and the early part of the thirteenth century, through the Crusades, through the Moorish civilization in Spain, through the Saracens in Sicily, through the Jews as translators and mediators, Aristotle invaded Christian Europe and transformed Christian philosophy. Albertus Magnus, Thomas Aquinas, Duns Scotus, William of Occam are the results of this transformation. The same thing holds true of the Jews. Their philosophizing career stands chronologically between that of their Arab teachers and their Christian disciples. And the line of their development was similar. It was parallel to that of the Arabs. First came Kalam in Saadia, Mukammas, the Karaites Al Basir and Jeshua ben Judah. Then Neo-Platonism and Kalam combined, or pure Neo-Platonism, in Bahya, Gabirol, Ibn Zaddik and the two Ibn Ezras, Abraham and Moses. In Judah Halevi, so far as philosophy is represented, we have Neo-Platonism and Aristotelianism. Finally in Ibn Daud and Maimonides, Neo-Platonism is reduced to the vanishing point, and Aristotelianism is in full view and in possession of the field. After Maimonides the only philosopher who deviates from the prescribed path and endeavors to uproot Aristotelian authority in Judaism is Crescas. All the rest stand by Aristotle and his major domo, Maimonides. This may seem like a purely formal and external mode of characterizing the development of philosophical thought. But the character of mediæval philosophy is responsible for this. Their ideal of truth as well as goodness was in the past. Knowledge was thought to have been discovered or revealed in the past,[227] and the task of the philosopher was to acquire what was already there and to harmonize contradictory authorities. Thus the more of the past literature that came to them, the greater the transformation in their own philosophy.