em; the problem, namely, of interpreting given
facts with reference to their function in the control of behavior. If
psychology is to justify its claim to the status of a science, it is in
duty bound to secure for itself both an objective criterion for the
adjudication of disputes which otherwise are of necessity interminable,
and a subject-matter that is not simply a heritage of metaphysical
prejudice, but a realm of fact that is attested by everyday observation
and experience.

III

Within recent years the doctrine that psychology is a science of
behavior has acquired a certain prominence. It is presupposed, of
course, that the behavior with which psychology is concerned is of a
distinctive sort; but the differentia is unfortunately the very thing
that the "behaviorist" has hitherto left out of account. In his revolt
against introspectionism, which has been accustomed to give to its
subject-matter a subjectivistic and "psychic" interpretation, he goes to
the other extreme and relies on behavior pure and simple. Being without
a serviceable differentia, he is unable to mark off the field of
psychology from contiguous territory. The selection of certain problems
within the general range of behavior, with no recognition of any
distinctive trait to guide and justify the selection, is hardly enough
to warrant a new science. Even an arbitrary principle of selection is
better than none, and it would, therefore, be quite as reasonable to
subdivide the field of botany in the interests of a new science, and
group together for separate botanical study those flowers which have
enabled poets to give symbolic expression to the beauty of women.

That the principle of selection is, in the end, the ability to modify
behavior through the anticipation of possible consequences, appears from
the fact that the category of stimulus and response is otherwise found
to be unworkable. It is true that in the simpler forms of behavior
stimulus and response may be correlated without practical difficulty.
But when we deal with what has been called "delayed overt response,"
the matter becomes more complicated and the theoretical difficulty
becomes more prominent. The behaviorist would not seriously undertake to
record everything that happens between stimulus and response. He
proceeds selectively, taking the relation of stimulus and response as
his clue. He is properly interested in the movements which result from
the application of the stimulus