w it uses this knowledge in thinking. This
much we shall be able to do, for it is often possible to describe a
process and discover its laws even when we cannot fully explain its
nature and origin. We know the process of digestion and assimilation,
and the laws which govern them, although we do not understand the
ultimate nature and origin of _life_ which makes these possible.

THE QUALITIES OF OBJECTS EXIST IN THE MIND.--Yet even in the relatively
simple description which we have proposed many puzzles confront us, and
one of them appears at the very outset. This is that the qualities which
we usually ascribe to objects really exist in our own minds and not in
the objects at all. Take, for instance, the common qualities of light
and color. The physicist tells us that what we see as light is
occasioned by an incredibly rapid beating of ether waves on the retina
of the eye. All space is filled with this ether; and when it is
light--that is, when some object like the sun or other light-giving body
is present--the ether is set in motion by the vibrating molecules of the
body which is the source of light, its waves strike the retina, a
current is produced and carried to the brain, and we see light. This
means, then, that space, the medium in which we see objects, is not
filled with light (the sensation), but with very rapid waves of ether,
and that the light which we see really occurs in our own minds as the
mental response to the physical stimulus of ether waves. Likewise with
color. Color is produced by ether waves of different lengths and degrees
of rapidity.

Thus ether waves at the rate of 450 billions a second give us the
sensation of red; of 472 billions a second, orange; of 526 billions a
second, yellow; of 589 billions a second, green; of 640 billions a
second, blue; of 722 billions a second, indigo; of 790 billions a
second, violet. What exists outside of us, then, is these ether waves of
different rates, and not the colors (as sensations) themselves. The
beautiful yellow and crimson of a sunset, the variegated colors of a
landscape, the delicate pink in the cheek of a child, the blush of a
rose, the shimmering green of the lake--these reside not in the objects
themselves, but in the consciousness of the one who sees them. The
objects possess but the quality of reflecting back to the eye ether
waves of the particular rate corresponding to the color which we ascribe
to them. Thus "red" objects, and no others, refle