ink
of it without my suggesting it to you. In either case _the cellular
activity in the visual area of the cortex is reproduced_ approximately
as it occurred in connection with the percept, and lo! an _image_ of the
watch flashes in your mind. An image is thus an approximate copy of a
former percept (or several percepts). It is aroused indirectly by means
of a nerve current coming by way of some other brain center, instead of
directly by the stimulation of a sense organ, as in the case of a
percept.

If, instead of seeking a more or less exact mental _picture_ of my
watch, you only think of its general _meaning_ and relations, the fact
that it is of gold, that it is for the purpose of keeping time, that it
was a present to me, that I wear it in my left pocket, you then have an
_idea_ of the watch. Our idea of an object is, therefore, the general
meaning of relations we ascribe to it. It should be remembered, however,
that the terms image and idea are employed rather loosely, and that
there is not yet general uniformity among writers in their use.

ALL OUR PAST EXPERIENCE POTENTIALLY AT OUR COMMAND.--Images may in a
certain sense take the place of percepts, and we can again experience
sights, sounds, tastes, and smells which we have known before, without
having the stimuli actually present to the senses. In this way all our
past experience is potentially available to the present. All the objects
we have seen, it is potentially possible again to see in the mind's eye
without being obliged to have the objects before us; all the sounds we
have heard, all the tastes and smells and temperatures we have
experienced, we may again have presented to our minds in the form of
mental images without the various stimuli being present to the
end-organs of the senses.

Through images and ideas the total number of objects in our experience
is infinitely multiplied; for many of the things we have seen, or heard,
or smelled, or tasted, we cannot again have present to the senses, and
without this power we would never get them again. And besides this fact,
it would be inconvenient to have to go and secure afresh each sensation
or percept every time we need to use it in our thought. While _habit_,
then, conserves our past experience on the physical side, the _image_
and the _idea_ do the same thing on the mental side.

3. INDIVIDUAL DIFFERENCES IN IMAGERY

IMAGES TO BE VIEWED BY INTROSPECTION.--The remainder of the description
of imag