election from among the whole mass
of sensory stimuli acting at any moment on the individual. Perception
is thus a fine example both of the "law of selection" and of the "law
of combination". [Footnote: See pp. 256, 263.] Perception is at once a
_combining_ response and an _isolating_ response.

We perceive a face--that means that we take the face as a unit, or
make a unitary response to the multiple stimuli coming from the face.
At the same time, in perceiving the face, we isolate it from its
background, or disregard the numerous other stimuli that are
simultaneously acting upon us. If we proceed to examine the face in
detail, we may isolate the nose and perceive that as a whole. We might
isolate still further and perceive a freckle on the nose, taking that
as a whole, or even observing separately its location, diameter, depth
of pigmentation, etc. Even if we went so far as to observe a single
speck of dust on the skin, in which case isolation would about reach
its maximum, combination would still stay in the game, for we should
either note {432} the location of the speck--which would involve
relating it to some part of the face--or we should contrast it with
the color of the skin, or in some similar way take the single stimulus
in relation with other present stimuli. Perception is always a unitary
response to an isolated assemblage of stimuli.

Consider these two opposite extremes: taking in the general effect of
the view from a mountain top, and perceiving the prick of a pin. In
the first case, combination is very much in evidence, but where is the
isolation? There is isolation, since internal bodily sensations, and
very likely auditory and olfactory sensations as well, are present but
do not enter into the view. In the case of the pin prick, isolation is
evident, but where does combination come in? It would not come into
the mere reflex of pulling the hand away, but perceiving the pin means
something more than reflex action. It means locating the sensation, or
noticing its quality or duration or something of that sort, and so
contrasting it with other sensations or relating it to them in some
way. To perceive one stimulus as related to another is to respond to
both together.

But in describing perception as a unitary response to an isolated
assemblage of stimuli, we have not differentiated it from a motor
response, for that, too, is often aroused by a few (or many) stimuli
acting together. What more can we say? I