As the "false dawn" of the Renaissance began to glimmer, a new source of heresy can be seen in the higher teaching--heretical in its own sphere--of Saracen philosophy, which under Aristotelian and Jewish influences had gone far while Christendom was sinking in a deepening darkness. The effects of Saracen contacts, acting on minds perhaps prepared by the doctrine of John Scotus, first became obvious in the pantheistic teaching of Amalrich of Bena and David Dinant at the end of the twelfth century. Amalrich was forced to abjure; and after his death his bones were dug up and burned (1209), and many of his followers burned alive; David of Dinant having to fly for his life. Then it was that a Council held at Paris vetoed all study of Aristotle at the university. Yet in 1237 the veto was withdrawn; and as Aristotle became the basis of the systematic theology of Thomas Aquinas (d. 1274), his philosophy was thenceforth the orthodox system in the schools. From the first it must have counted for indirect scepticism; and in the great Summa Theologiæ of Thomas himself are to be seen abundant traces of the new doubt of the age, much of it set up by reflection on the spectacle of conflicting religious dogmatisms in the Crusades, some of it by Saracen philosophy, especially that of Averroës [Ibn Roshd]. In Sicily and Southern Italy, which under Frederick II were the special seat of this doubt and of the tendency to tolerance which it generated, the spirit of reason ultimately fared ill; but thenceforth an element of skepticism pervades the higher life of Europe. Saracen science, medical, chemical, and astronomical--the virtual foundation of all the modern science of Europe--tended in the same direction. In Italy, in particular, respect for the Church and papacy almost ceased to exist among educated men; and the revival of such specific heresies as disbelief in immortality and belief in the eternity of matter prepared the way for simple deism.
But against all such heresy the Church could hold its ground in virtue of its vast vested interests, as well as of the subjection of the mass, superstitious even when irreverent. The practical danger to the Church's power lay first in the growth of anti-clerical feeling among people with religious instincts, and secondarily in the anti-clerical economic interest of the nobility and upper classes in all the northern countries. What delayed disaster was the slowness of the two hostile elements to combine.