the
establishment of the identity of the reactions of animals and
plants to light proved the untenability of this view and at the
same time offered a different conception of reflexes. The
flight of the moth into the flame is a typical reflex process.
The light stimulates the peripheral sense organs, the stimulus
passes to the central nervous system, and from there to the
muscles of the wings, and the moth is caused to fly into the
flame. This reflex process agrees in every point with the
heliotropic effects of light on plant organs. Since plants
possess no nerves, this identity of animal with plant
heliotropism can offer but one inference--these heliotropic
effects must depend upon conditions which are common to both
animals and plants.

On the other hand, Watson, in his _Introduction to Comparative
Psychology_, defines the reflex as "a unit of analysis of instinct," and
this means that instinctive actions in man and in animals may be
regarded as combinations of simple reflex actions, that is to say of
"fairly definite and generally predictable but unlearned responses of
lower and higher organisms to stimuli." Many of these reflex responses
are not fixed, as they were formerly supposed to be, but "highly
unstable and indefinite." This fact makes possible the formation of
habits, by combination and fixation of these inherited responses.

These views in the radical form in which they are expressed by Loeb and
Watson have naturally enough been the subject of considerable
controversy, both on scientific and sentimental grounds. They seem to
reduce human behavior to a system of chemical and physical reactions,
and rob life of all its spiritual values. On the other hand, it must be
remembered that human beings, like other forms of nature, have this
mechanical aspect and it is precisely the business of natural science to
discover and lay them bare. It is only thus that we are able to gain
control over ourselves and of others. It is a matter of common
experience that we do form habits and that education and social control
are largely dependent upon our ability to establish habits in ourselves
and in others. Habit is, in fact, a characteristic example of just what
is meant by "mechanism," in the sense in which it is here used. It is
through the fixation of habit that we gain that control over our
"original nature," which lifts us above the brutes and gives human