But, however it may be with the child in the earlier stages of its development, we must all admit that the mature man does consciously recognize that the world in which he finds himself is a world that contains minds as well as bodies.  It never occurs to him to doubt that there are bodies, and it never occurs to him to doubt that there are minds.

Does he not perceive that he has a body and a mind?  Has he not abundant evidence that his mind is intimately related to his body?  When he shuts his eyes, he no longer sees, and when he stops his ears, he no longer hears; when his body is bruised, he feels pain; when he wills to raise his hand, his body carries out the mental decree.  Other men act very much as he does; they walk and they talk, they laugh and they cry, they work and they play, just as he does.  In short, they act precisely as though they had minds like his own.  What more natural than to assume that, as he himself gives expression, by the actions of his body, to the thoughts and emotions in his mind, so his neighbor does the same?

We must not allow ourselves to underrate the plain man’s knowledge either of bodies or of minds.  It seems, when one reflects upon it, a sufficiently wonderful thing that a few fragmentary sensations should automatically receive an interpretation which conjures up before the mind a world of real things; that, for example, the little patch of color sensation which I experience when I turn my eyes toward the window should seem to introduce me at once to a world of material objects lying in space, clearly defined in magnitude, distance, and direction; that an experience no more complex should be the key which should unlock for me the secret storehouse of another mind, and lay before me a wealth of thoughts and emotions not my own.  From the poor, bare, meaningless world of the dawning intelligence to the world of common thought, a world in which real things with their manifold properties, things material and things mental, bear their part, is indeed a long step.

And we should never forget that he who would go farther, he who would strive to gain a better knowledge of matter and of mind by the aid of science and of philosophical reflection, must begin his labors on this foundation which is common to us all.  How else can he begin than by accepting and more critically examining the world as it seems revealed in the experience of the race?

8.  Scientific knowledge.—­Still, the knowledge of the world which we have been discussing is rather indefinite, inaccurate, and unsystematic.  It is a sufficient guide for common life, but its deficiencies may be made apparent.  He who wishes to know matter and mind better cannot afford to neglect the sciences.

Now, it is important to observe that although, when the plain man grows scientific, great changes take place in his knowledge of things, yet his way of looking at the mind and the world remains in general much what it was before.  To prevent this statement from being misunderstood, I must explain it at some length.