In the Middle Ages there gradually grew up rather a sharp distinction between those things that can be known through the unaided reason and those things that can only be known through a supernatural revelation. The term "philosophy" came to be synonymous with knowledge attained by the natural light of reason. This seems to imply some sort of a limitation to the task of the philosopher. Philosophy is not synonymous with all knowledge. But we must not forget to take note of the fact that philosophy, even with this limitation, constitutes a pretty wide field. It covers both the physical and the moral sciences. Nor should we omit to notice that the scholastic philosopher was at the same time a theologian. Albert the Great and St. Thomas Aquinas, the famous scholastics of the thirteenth century, had to write a "_Summa Theologiae_," or system of theology, as well as to treat of the other departments of human knowledge. Why were these men not overwhelmed with the task set them by the tradition of their time? It was because the task was not, after all, so great as a modern man might conceive it to be. Gil Blas, in Le Sage's famous romance, finds it possible to become a skilled physician in the twinkling of an eye, when Dr. Sangrado has imparted to him the secret that the remedy for all diseases is to be found in bleeding the patient and in making him drink copiously of hot water. When little is known about things, it does not seem impossible for one man to learn that little. During the Middle Ages and the centuries preceding, the physical sciences had a long sleep. Men were much more concerned in the thirteenth century to find out what Aristotle had said than they were to address questions to nature. The special sciences, as we now know them, had not been called into existence. 5. THE MODERN PHILOSOPHY.--The submission of men's minds to the authority of Aristotle and of the church gradually gave way. A revival of learning set in. Men turned first of all to a more independent choice of authorities, and then rose to the conception of a philosophy independent of authority, of a science based upon an observation of nature, of a science at first hand. The special sciences came into being. But the old tradition of philosophy as universal knowledge remained. If we pass over the men of the transition period and turn our attention to Francis Bacon (1561-1626) and Rene Descartes (1596-1650), the two who are commonly regarded as heading the list of the modern philosophers, we find both of them assigning to the philosopher an almost unlimited field.