But let me gather up in a few words the purport of what has been said above. Philosophy once meant the whole body of scientific knowledge. Afterward it came to mean the whole body of knowledge which could be attained by the mere light of human reason, unaided by revelation. The several special sciences sprang up, and a multitude of men have for a long time past devoted themselves to definite limited fields of investigation with little attention to what has been done in other fields. Nevertheless, there has persisted the notion of a discipline which somehow concerns itself with the whole system of things, rather than with any limited division of that broad field. It is a notion not peculiar to the disciples of Spencer. There are many to whom philosophy is a "_Weltweisheit_," a world-wisdom. Shall we say that this is the meaning of the word philosophy now? And if we do, how shall we draw a line between philosophy and the body of the special sciences? Perhaps the most just way to get a preliminary idea of what philosophy means to the men of our time is to turn away for the time being from the definition of any one man or group of men, and to ask ourselves what a professor of philosophy in an American or European university is actually supposed to teach. It is quite clear that he is not supposed to be an Aristotle. He does not represent all the sciences, and no one expects him to lecture on mathematics, mechanics, physics, chemistry, zooelogy, botany, economics, politics, and various other disciplines. There was a time when he might have been expected to teach all that men could know, but that time is long past. Nevertheless, there is quite a group of sciences which are regarded as belonging especially to his province; and although a man may devote a large part of his attention to some one portion of the field, he would certainly be thought remiss if he wholly neglected the rest. This group of sciences includes logic, psychology, ethics and aesthetics, metaphysics, and the history of philosophy. I have not included epistemology or the "theory of knowledge" as a separate discipline, for reasons which will appear later (Chapter XIX); and I have included the history of philosophy, because, whether we care to call this a special science or not, it constitutes a very important part of the work of the teacher of philosophy in our day. Of this group of subjects the student who goes to the university to study philosophy is supposed to know something before he leaves its walls, whatever else he may or may not know.