have observed, and suggest how they
may be cured.

6. Make a list of from ten to twenty habits which you think the school
and its work should especially cultivate. What ones of these are the
schools you know least successful in cultivating? Where does the trouble
lie?

CHAPTER VI

SENSATION

We can best understand the problems of sensation and perception if we
first think of the existence of two great worlds--the world of physical
nature without and the world of mind within. On the one hand is our
material environment, the things we see and hear and touch and taste and
handle; and on the other hand our consciousness, the means by which we
come to know this outer world and adjust ourselves to it. These two
worlds seem in a sense to belong to and require each other. For what
would be the meaning or use of the physical world with no mind to know
or use it; and what would be the use of a mind with nothing to be known
or thought about?

1. HOW WE COME TO KNOW THE EXTERNAL WORLD

There is a marvel about our coming to know the external world which we
shall never be able fully to understand. We have come by this knowledge
so gradually and unconsciously that it now appears to us as commonplace,
and we take for granted many things that it would puzzle us to explain.

KNOWLEDGE THROUGH THE SENSES.--For example, we say, "Of course I see
yonder green tree: it is about ten rods distant." But why "of course"?
Why should objects at a distance from us and with no evident connection
between us and them be known to us at all merely by turning our eyes in
their direction when there is light? Why not rather say with the blind
son of Professor Puiseaux of Paris, who, when asked if he would like to
be restored to sight, answered: "If it were not for curiosity I would
rather have long arms. It seems to me that my hands would teach me
better what is passing in the moon than your eyes or telescopes."

We listen and then say, "Yes, that is a certain bell ringing in the
neighboring village," as if this were the most simple thing in the
world. But why should one piece of metal striking against another a mile
or two away make us aware that there is a bell there at all, let alone
that it is a certain bell whose tone we recognize? Or we pass our
fingers over a piece of cloth and decide, "That is silk." But why,
merely by placing our skin in contact with a bit of material, should we
be able to know its quality, much less that it is