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 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 how 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