But it is possible, even for one who is not acquainted with the whole body of facts presented in a science, to take careful note of the assumptions upon which that science rests, to analyze the concepts of which it makes use, to mark the methods which it employs, and to gain a fair idea of its scope and of its relation to other sciences. Such a reflection upon our scientific knowledge is philosophical reflection, and it may result in a classification of the sciences, and in a general view of human knowledge as a whole. Such a view may be illuminating in the extreme; it can only be harmful when its significance is misunderstood. But, it may be argued, why may not the man of science do all this for himself? Why should he leave it to the philosopher, who is presumably less intimately acquainted with the sciences than he is? To this I answer: The work should, of course, be done by the man who will do it best. All our subdivision of labor should be dictated by convenience. But I add, that experience has shown that the workers in the special sciences have not as a rule been very successful when they have tried to philosophize. Science is an imperious mistress; she demands one's utmost efforts; and when a man turns to philosophical reflection merely "by the way," and in the scraps of time at his disposal after the day's work is done, his philosophical work is apt to be rather superficial. Moreover, it does not follow that, because a man is a good mathematician or chemist or physicist, he is gifted with the power of reflective analysis. Then, too, such men are apt to be imperfectly acquainted with what has been done in the past; and those who are familiar with the history of philosophy often have occasion to remark that what is laid before them, in ignorance of the fact that it is neither new nor original, is a doctrine which has already made its appearance in many forms and has been discussed at prodigious length in the centuries gone by. In certain sciences it seems possible to ignore the past, to a great extent, at least. What is worth keeping has been kept, and there is a solid foundation on which to build for the future. But with reflective thought it is not so. There is no accepted body of doctrine which we have the right to regard as unassailable. We should take it as a safe maxim that the reflections of men long dead _may_ be profounder and more worthy of our study than those urged upon our attention by the men of our day.