always oscillating about the threshold of obscure consciousness, but to
the higher sensations connected with the special organs of perception.
The student in optics soon makes the startling discovery that his field
of vision has all through his life been haunted with weird shapes which
have never troubled the serenity of his mind just because they have
never been distinctly attended to.

The immediate result of this process of directing the keen glance of
attention to a sensation is to give it greater force and distinctness.
By attending to it we discriminate it from other feelings present and
past, and classify it with like sensations previously received. Thus, if
I receive a visual impression of the colour orange, the first
consequence of attending to it is to mark it off from other
colour-impressions, including those of red and yellow. And in
recognizing the peculiar quality of the impression by applying to it the
term orange, I obviously connect it with other similar sensations called
by the same name. If a sensation is perfectly new, there cannot, of
course, be this process of classifying, and in this case the closely
related operation of discriminating it from other sensations is less
exactly performed. But it is hardly necessary to remark that, in the
mind of the adult, under ordinary circumstances, no perfectly new
sensation ever occurs.

When the sensation, or complex sensation, is thus defined and
recognized, there follows the process of interpretation, by which I mean
the taking up of the impression as an element into the complex mental
state known as a percept. Without going into the philosophical question
of what this process of synthesis exactly means, I may observe that, by
common consent, it takes place to a large extent by help of a
reproduction of sensations of various kinds experienced in the past.