that our sensations always
carry with them an implicit reference to an external object. Leaving,
therefore, to the scientific psychologist to consider whether it is
possible to have a pure sensation, we shall treat sensation as the
recognition of a quality which is at least vaguely referred to an
external object. In other words, sensation is a medium by which we are
brought into relation with real things existing independently of our
sensations.

=Perception Involves Sensation Element.=--Moreover, an object is
perceived as present here and now only because it is revealed to us
through one or more of the senses. When, for instance, I reach out my
hand in the dark room and receive a sensation of touch, I perceive the
table as present before me. When I receive a sensation of sound as I
pass by the church, I perceive that the organ is being played. When I
receive a colour sensation from the store window, I say that I perceive
oranges. Perception, therefore, involves the referring of the sensuous
state, or image, to an external thing, while in adult life sensation is
never accepted by our attention as satisfactory unless it is referred to
something we regard as immediately presenting itself to us by means of
the sensation. It is on account of this evident interrelation of the two
that we speak of a process of sense perception.

=Perception an Acquired Power.=--On the other hand, however,
investigation will show that this power to recognize explicitly the
existence of an external object through the presentation of a sensation,
was not at first possessed by the mind. The ability thus to perceive
objects represents, therefore, an acquirement on the part of the
individual. If a person, although receiving merely sensations of colour
and light, is able to say, "Yonder is an orange," he is evidently
interpreting, or giving meaning to, the present sensations largely
through past experience; for the images of colour and light are
accepted by the mind as an indication of the presence of an external
thing from which could be derived other images of taste, smell, etc.,
all of which go to make up the idea "orange." An ordinary act of
perception, therefore, must involve not merely sensation, but also an
interpretation of sensation through past experience. It is, in fact,
because the recognition of an external object involves this conscious
interpretation of the sensuous impressions, that people often suffer
delusion. When the traveller