upon
appearances, his judgment is active; it compares, and infers relations
it does not perceive; and it may then be mistaken. He will need
experience to prevent or correct such mistakes. Show your pupil clouds
passing over the moon at night, and he will think that the moon is
moving in an opposite direction, and that the clouds are at rest. He
will the more readily infer that this is the case, because he usually
sees small objects, not large ones, in motion, and because the clouds
seem to him larger than the moon, of whose distance he has no idea.
When from a moving boat he sees the shore at a little distance, he
makes the contrary mistake of thinking that the earth moves. For,
unconscious of his own motion, the boat, the water, and the entire
horizon seem to him one immovable whole of which the moving shore is
only one part.

The first time a child sees a stick half immersed in water, it seems to
be broken. The sensation is a true one, and would be, even if we did
not know the reason for this appearance. If therefore you ask him what
he sees, he answers truly, "A broken stick," because he is fully
conscious of the sensation of a broken stick. But when, deceived by
his judgment, he goes farther, and after saying that he sees a broken
stick, he says again that the stick really is broken, he says what is
not true; and why? Because his judgment becomes active; he decides no
longer from observation, but from inference, when he declares as a fact
what he does not actually perceive; namely, that touch would confirm
the judgment based upon sight alone.

The best way of learning to judge correctly is the one which tends to
simplify our experience, and enables us to make no mistakes even when
we dispense with experience altogether. It follows from this that
after having long verified the testimony of one sense by that of
another, we must further learn to verify the testimony of each sense by
itself without appeal to any other. Then each sensation at once
becomes an idea, and an idea in accordance with the truth. With such
acquisitions I have endeavored to store this third period of human life.

To follow this plan requires a patience and a circumspection of which
few teachers are capable, and without which a pupil will never learn to
judge correctly. For example: if, when he is misled by the appearance
of a broken stick, you endeavor to show him his mistake by taking the
stick quickly out of the water, you may p