cloth and that its
threads were originally spun by an insect? Or we take a sip of liquid
and say, "This milk is sour." But why should we be able by taking the
liquid into the mouth and bringing it into contact with the mucous
membrane to tell that it is milk, and that it possesses the quality
which we call _sour_? Or, once more, we get a whiff of air through the
open window in the springtime and say, "There is a lilac bush in bloom
on the lawn." Yet why, from inhaling air containing particles of lilac,
should we be able to know that there is anything outside, much less that
it is a flower and of a particular variety which we call lilac? Or,
finally, we hold a heated flatiron up near the cheek and say, "This is
too hot! it will burn the cloth." But why by holding this object a foot
away from the face do we know that it is there, let alone knowing its
temperature?

THE UNITY OF SENSORY EXPERIENCE.--Further, our senses come through
experience to have the power of fusing, or combining their knowledge, so
to speak, by which each expresses its knowledge in terms of the others.
Thus we take a glance out of the window and say that the day looks cold,
although we well know that we cannot see _cold_. Or we say that the
melon sounds green, or the bell sounds cracked, although a _crack_ or
_greenness_ cannot be heard. Or we say that the box feels empty,
although _emptiness_ cannot be felt. We have come to associate cold,
originally experienced with days which look like the one we now see,
with this particular appearance, and so we say we see the cold; sounds
like the one coming from the bell we have come to associate with cracked
bells, and that coming from the melon with green melons, until we say
unhesitatingly that the bell sounds cracked and the melon sounds green.
And so with the various senses. Each gleans from the world its own
particular bit of knowledge, but all are finally in a partnership and
what is each one's knowledge belongs to every other one in so far as the
other can use it.

THE SENSORY PROCESSES TO BE EXPLAINED.--The explanation of the ultimate
nature of knowledge, and how we reach it through contact with our
material environment, we will leave to the philosophers. And battles
enough they have over the question, and still others they will have
before the matter is settled. The easier and more important problem for
us is to describe the _processes_ by which the mind comes to know its
environment, and to see ho