Throughout the preparation of this elementary text I have tried to write with the human animal in front of me. I have put down only those things that any properly trained individual can observed - it does not take a psychologist qua psychologist to study human activity, but it does take a trained scientist and one trained along special lines. In this conclusion I am in hearty agreement with Cattell's St. Louis address. The young student of behavioristic psychology has to endure no holy vigil before beginning to use psychological material and methods, nor does he at any time have to pass through secret initiation ceremonies before beginning research work. The key which will unlock the door of any other scientific structure will unlock the door of psychology. The differences among the various sciences now are only those necessitated by the division of labor. Until psychology recognizes this and discards everything which cannot be stated in the universal terms of science, she does not deserve her place in the sun. Behavior psychology does make this attempt for the first time. It has been called physiology, muscle-twitch psychology and biology, but if it helps us to throw off the shackles of the present-day conventional psychology and teaches us to face the human being as he is and to deal frankly with him, what name it is given will not be a matter of much consequence. Nor does the author claim behavior psychology as a creation of his own. It has had rapid development and is a direct outgrowth of the work on animal behavior. It is purely an American production and the attempts of Titchener to tie it up with past "revolts" in psychology and of Miss Washburn to link it with the so-called objectivism of Beer, Bethe, von Uexküll, Nuel and other continental writers are based upon an insufficient knowledge of its tenets. Those so-called objectivists, so far as concerns their human psychology, - and this is true of Bechterew as well, - are perfectly orthodox parallelists.