Nevertheless the more we reflect on that material, the more evident
does it become that the plain man cannot be wrong in believing in the
external world which seems revealed in his experiences. We find that
all attempts to discredit it rest upon the implicit assumption of its
existence, and fall to the ground when that existence is honestly
denied. So our problem changes its form. We no longer ask: Is there
an external world? but rather: _What_ is the external world, and how
does it differ from the world of mere ideas?


[1] "The Grammar of Science," 2d Ed., London, 1900, pp. 60-63.




CHAPTER IV

SENSATIONS AND "THINGS"

15. SENSE AND IMAGINATION.--Every one distinguishes between things
perceived and things only imagined. With open eyes I see the desk
before me; with eyes closed, I can imagine it. I lay my hand on it and
feel it; I can, without laying my hand on it, imagine that I feel it.
I raise my eyes, and see the pictures on the wall opposite me; I can
sit here and call before my mind the image of the door by which the
house is entered.

What is the difference between sense and imagination? It must be a
difference of which we are all somehow conscious, for we unhesitatingly