Working speculatively with psychological material there is a risk of being sacrificed to the general misunderstanding which bestows the value of an objective theory upon the line of psychological evolution thus elaborated. So many people feel themselves in this way at pains to find grounds whether such a theory is correct or not. Those who are particularly brilliant even discover that the fundamental concepts can be traced back to Heraclitus or some one even earlier. Let me confide to these knowing folk that the fundamental ideas employed in the constructive method stretch back even beyond any historical philosophy, viz. to the dynamic "views" of primitive peoples. If the result of the constructive method were scientific theory, it would go very ill with it, for then it would be a falling back to the deepest superstition. But since the constructive method results in something far removed from scientific theory the great antiquity of the basic concepts therein must speak in favour of its extreme correctness. Not until the constructive method has presented us with much practical experience can we come to the construction of a _scientific theory, a theory of the psychological lines of development_. But we must first of all content ourselves with confirming these lines individually. FOREWORD TO CHAPTER XIV This essay was originally written in 1913, when I limited myself entirely to presenting an essential part of the psychological point of view inaugurated by _Freud_. A few months ago my Swiss publisher asked for a second and revised edition. The many and great changes which the last few years have brought about in our understanding of the psychology of the unconscious necessitated a substantial enlargement of my essay. In this new edition some expositions about _Freud's_ theories are shortened, whilst _Adler's_ psychological views are more fully considered, and--so far as the scope of this paper permits--a general outline of my own views are given. I must at the outset draw the reader's attention to the fact that this is no longer an easy "popular" scientific paper, but a presentation making great demands upon the patience and attention of the reader. The material is extremely complicated and difficult. I do not for a moment deceive myself into thinking this contribution is in any way conclusive or adequately convincing. Only detailed scientific treatises about the various problems touched upon in these pages could really do justice to the subject. Any one who wishes to go deeply into the questions that are raised here must be referred to the special literature of the subject. My attention is solely to give the orientation in regard to the newest concepts of the inner nature of unconscious psychology. I consider the subject of the unconscious to be specially important and opportune at this moment. In my opinion, it would be a great loss if this problem, concerning every one so closely as it does, were to disappear from