Our task here is, therefore, to lay a broad psychological foundation. We must carefully inquire how the modern psychologist looks on mental life and how the inner experiences appear from such a psychological standpoint. The first chapters of this volume may appear like a long, tiresome way around before we come to our goal, the study of the psychotherapeutic agencies. And yet it is the only possible way to overcome the superficiality with which the discussion is too often carried on; we must understand exactly how the psychological analysis and explanation of the scientist differ from the popular point of view. After studying in this spirit the foundation of psychotherapy, we shall carefully examine the practical work, its methods and its results, its possibilities and its limitations. We shall inquire finally into the place which it has to take, looking back upon its history, criticising the present status and outlining the development which has to set in for the future, if a haphazard zigzag movement is not to destroy this great agency for human welfare by transforming it into a source of superstition and bodily danger. PART I THE PSYCHOLOGICAL BASIS OF PSYCHOTHERAPY II THE AIM OF PSYCHOLOGY The only safe basis of psychotherapy is a thorough psychological knowledge of the human personality. Yet such a claim has no value until it is entirely clear what is meant by psychological knowledge. We can know man in many ways. Not every study of man's inner life is psychology and the careless mixing of different ways of dealing with man's inner life is largely responsible for the vagueness which characterizes the popular literature of psychotherapy. It is not enough to say that a statement is true or not true. It may be true under one aspect and entirely meaningless under another. For instance, a minister's discussion of man's energies may be full of deep truth and may be inspiring; and yet it may not contain the slightest contribution to a really psychological knowledge of those energies, and would mislead entirely the physician were he to base his treatment of human energies on such a religious interpretation.