ed that after the brain has had an excitation giving
rise to sensation, it is capable of reviving this excitation later. This
renewal or revival of a brain excitation gives us an experience
resembling the original sensation, only usually fainter and less stable.
This revived experience is called _image_ or _idea_. The general process
of retention and revival of experience is, as we have seen, known as
memory. An idea, then, is a bit of revived experience. A perception is a
bit of immediate or primary experience. I am said to perceive a chair if
the chair is present before me, if the light reflected from the chair is
actually exciting my retinas. I have an _idea_ of the chair when I
_seem_ to see it, when the chair is not before me or when my eyes are
shut. These distinctions were pointed out in the preceding chapter. Let
us now proceed to carry our study of ideas further.

=Association of Ideas.= The subject of the association of ideas can best
be introduced by an experiment. Take a paper and pencil, and think of
the word "horse." Write this word down, and then write down other words
that come to mind. Write them in the order in which they come to mind.
Do this for three or four minutes, and try the experiment several times,
beginning with a different word each time. Make a study of the lists of
words. Compare the different lists and the lists written by different
students.

In the case of the writer, the following words came to mind in the first
few seconds: horse, bridle, saddle, tail, harness, buggy, whip, man,
sky, stars, sun, ocean. Why did these words come, and why did they come
in that order? Why did the idea "horse" suggest the idea "bridle"? And
why did "bridle" suggest "saddle"? Is there something in the nature of
ideas that couples them with certain other ideas and makes them _always_
suggest the other ideas? No, there is not. Ideas become coupled together
in our experience, and the coupling is in accordance with our
experience. Things that are together in our experience become coupled
together as ideas. The idea "horse" may become coupled with any other
idea. The general law of the association of ideas is this: Ideas are
joined together in memory or revived experience as they were joined in
the original or perceptive experience.

But the matter is complicated by the fact that things are experienced in
different connections in perceptive experience. I do not always
experience "horse" together with "bridle."