hat a distinctive field can be marked off for
psychological enterprise. When we say that the flame is hot, the stone
hard, and the ice cold and slippery, we are describing objects and
nothing more. These qualities are, indeed, anticipations of future
possibilities, but this means simply that the objects are described in
terms of their properties or capacities as stimuli of the organism. Such
an account leaves out of consideration certain changes which things
undergo when they exercise the function of controlling or directing
changes in the adjustment of the body. A quality, such as "sharp" or
"hot," is not mental or constituted by consciousness, but the function
of the quality in giving direction to behavior through certain changes
which it undergoes is consciousness. The changes that take place in
things as a result of association, attention, or memory, are changes
that have no significance, save with regard to their function as stimuli
to new adjustments. Psychology, therefore, is properly a study of the
conditions which determine the change or development of stimuli; more
specifically it is a study of the conditions which govern such processes
as those by which problems are solved, lessons are memorized, habits and
attitudes are built up, and decisions are reached. To call such study
"applied" psychology is to misunderstand the proper scope and purpose of
the subject. Psychology frequently has occasion to draw extensively upon
physics and physiology, but it has its own problem and its own method of
procedure.

That this view of conscious behavior should involve an extensive
reinterpretation of familiar facts is altogether natural and inevitable.
If consciousness is a form of control, the question, for example, what
is "in" consciousness and what is not must be interpreted with reference
to this function of control. In a sense we perceive many things to
which we are not paying attention, such as the light in the room or the
familiar chairs and bookcases. These are perceived "marginally," as we
say, in the sense that the presence of these objects affects the total
adjustment of the moment in such a way that the experience _would_
become a clue to these objects if they were withdrawn. And similarly we
may speak of marginal sensations of strain or movement, to indicate
possible clues to certain bodily activities which are factors in the
process. These marginal perceptions or images are not actual existences,
but are symb