How, then, does metaphysics differ from philosophy?  The difference becomes clear to us when we realize that the word philosophy has a broader and looser signification, and that metaphysics is, so to speak, the core, the citadel, of philosophy.

We have seen (Chapter II) that the world and the mind, as they seem to be presented in the experience of the plain man, do not stand forth with such clearness and distinctness that he is able to answer intelligently the questions we wish to ask him regarding their nature.  It is not merely that his information is limited; it is vague and indefinite as well.  And we have seen, too, that, however the special sciences may increase and systematize his information, they do not clear away such vagueness.  The man still uses such concepts as “inner” and “outer,” “reality,” “the mind,” “space,” and “time,” with no very definite notion of what they mean.

Now, the attempt to clear away this vagueness by the systematic analysis of such concepts—­in other words, the attempt to make a thorough analysis of our experience—­is metaphysics.  The metaphysician strives to limit his task as well as he may, and to avoid unnecessary excursions into the fields occupied by the special sciences, even those which lie nearest to his own, such as psychology and ethics.  There is a sense in which he may be said to be working in the field of a special science, though he is using as the material for his investigations concepts which are employed in many sciences; but it is clear that his discipline is not a special science in the same sense in which geometry and physics are special sciences.

Nevertheless, the special sciences stand, as we have already seen in the case of several of them, very near to his own.  If he broadens his view, and deliberately determines to take a survey of the field of human knowledge as illuminated by the analyses that he has made, he becomes something more than a metaphysician; he becomes a philosopher.

This does not in the least mean that he becomes a storehouse of miscellaneous information, and an authority on all the sciences.  Sometimes the philosophers have attempted to describe the world of matter and of mind as though they possessed some mysterious power of knowing things that absolved them from the duty of traveling the weary road of observation and experiment that has ended in the sciences as we have them.  When they have done this, they have mistaken the significance of their calling.  A philosopher has no more right than another man to create information out of nothing.

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.