f the facts, adjusting himself to
them and also shaping them to suit himself. His actions are governed
by the facts perceived, at the same time that they are governed by his
own desires. Ascertaining how the facts stand, he takes a hand and
manipulates them. He is constantly coming to know {421} fresh facts,
and constantly doing something new with them. His life is a voyage of
discovery, and at the same time a career of invention.

Discovery and invention!--high-sounding words, still they are
applicable to everyday life. The facts observed may not be absolutely
new, but at least they have always to be verified afresh, since action
needs always to take account of present reality. The invention may be
very limited in scope, but seldom does an hour pass that does not call
for doing something a little out of the ordinary, so as to escape from
a fresh trap or pluck fruit from a newly discovered bough. All of our
remaining chapters might, with a little forcing, be pigeonholed under
these two great heads. Discovery takes its start with the child's
instinctive exploratory activity, and invention with his manipulation,
and these two tendencies, perhaps at bottom one, remain closely
interlinked throughout.

Some Definitions

_Perception_ is the culmination of the process of discovery. Discovery
usually requires exploration, a search for facts; and it requires
attention, which amounts to finding the facts or getting them
effectively presented; and perception then consists in knowing the
presented facts.

When the facts are presented to the senses, we speak of "sense
perception". If they are presented to the eye, we speak of visual
perception; if to the ear, of auditory perception, etc. But when we
speak of a fact as being "presented" to the eye or ear, we do not
necessarily mean that it is directly and completely presented; it may
only be indicated. We may have before the eyes simply a _sign_ of some
fact, but perceive the fact which is the _meaning_ of the sign. We
look out of the window and "see it is wet to-day", though wetness is
something to be felt rather than seen; {422} having previously
observed how wet ground looks, we now respond promptly to the visual
appearance by knowing the indicated state of affairs. In the same way,
we say that we "hear the street car", though a street car, we must
admit, is not essentially a noise. What we hear, in strictness, is a
noise, but we respond to the noise by perceiving the prese