"This volume on psychotherapy belongs to a series of books which I am writing to discuss for a wider public the practical applications of modern psychology. The first book, called "On the Witness Stand," studied the relations of scientific psychology to crime and the law courts. This new book deals with the relations of psychology to medicine. Others discussing its relations to education, to social problems, to commerce and industry will follow soon. For popular treatment I divide applied psychology into such various, separated books because they naturally address very different audiences. That which interests the lawyer does not concern the physician, and again the school-teacher has his own sphere of interests. Moreover the different subjects demand a different treatment. The problems of psychology and law were almost entirely neglected. I was anxious to draw wide attention to this promising field and therefore I chose the form of loose popular essays without any aim towards systematic presentation of the subject. As to psychology and medicine almost the opposite situation prevails. There is perhaps too much talk afloat about psychotherapy, the widest circles cultivate the discussion, the magazines overflow with it. The duty of the scientific psychologist is accordingly not to stir up interest in this topic but to help in bringing this interest from mere gossip, vague mysticism, and medical amateurishness to a clear understanding of principles. What is needed in this time of faith cures of a hundred types is to deal with the whole circle of problems in a serious, systematic way and to emphasize the aspect of scientific psychological theory."