But, in the second place, any such harmonisation could only be carried out by some demarcation of territory. The earlier orthodox writers like Anselm, as we have seen, did not hesitate to attempt a philosophical explanation of the doctrine of the Trinity. But Aristotle and his Arabian commentators were monotheistic, and consequently the reconciliation between the Aristotelian philosophy and the Christian faith could only be effected by distinguishing between natural and revealed religion. The truths of the former were demonstrable by reason, of which Aristotle was the supreme guide. The truths of the latter were mysteries to be accepted on an equally good though different authority. By such methods these later schoolmen excepted and accepted the doctrines of the Trinity and the Incarnation, though they allowed the doctrine of the existence of God to be susceptible of logical proof. But notwithstanding these exceptions, the teaching of the Dominicans was a wonderful attempt to abolish the inevitable dualism between faith and reason. [Sidenote: Thomists and Scotists.] The history of Scholasticism after Thomas Aquinas is largely occupied by an account of the quarrel between the rival schools of Thomists and Scotists. The great teacher of the generation after St. Thomas was a Franciscan, Duns Scotus, the "Subtle Doctor," who taught at Oxford and Paris and died in 1308. His teaching differed in two ways from that of his Dominican predecessor. In the first place he excepted a larger number of theological doctrines as not being capable of philosophic proof, so that his teaching tended to bring back and to emphasise the dualism between faith and reason. It is for this reason that his system has been considered as the beginning of the decline of Scholasticism. In the second place, the real quarrel between Thomists and Scotists centred round the question of the freedom of the will. The followers of St. Thomas maintained that although the will is to some extent subordinate to the reason, yet it is free to determine its own course of action after a process of rational comparison, by contrast with the animals which act on the impulse of the moment. The Scotists, on the other hand, taught that what is called the will is merely a name for the possibility of determining without motive in either of two opposite directions. The importance of this difference of view consisted in this--that whereas the Thomists held that God subjects His will to a rational determination and therefore commands what is good because it is good, the Scotist taught that good is so because God wills it; if He chose to will the exact opposite, that would be equally good--in other words, he attributed to God an entirely arbitrary will. The two greatest disciples of St. Thomas were Dante and the Franciscan Roger Bacon (1214-92), the latter of whom fell into disfavour with the superiors of his own Order in consequence of his scientific studies, and spent many years at the end of his life