He who attempts to sketch the "Outlines of a Psychological History of the Development of Mankind" necessarily incurs a heavy indebtedness, as regards his material, to various more specialized sciences. The success with which the data have been sifted in the present instance and the extent to which the author has repaid the special sciences in terms of serviceable principles of interpretation, must, to a certain extent, be left to the determination of those who are engaged in these specific fields. Human beliefs and institutions, however, as well as all products of art and modes of labour, of food-getting, of marriage, of warfare, etc.--in short, all elements of human culture--even though subject to natural conditions of various sorts, are essentially mental processes or the expression of psychical activities. Hence no theory relating to these phenomena is acceptable, or even respectable, that does violence to well-established psychological principles. The unpsychological character of many of the hypotheses that still abound in ethnological, sociological, and historical literature, in itself renders necessary such discussions as those comprised within the present volume. One of the very valuable, even though not novel, features of the "Elements," therefore, is its clear exposure of the untenability of rationalistic and other similarly erroneous types of explanation. The dependence of folk psychology, as conceived by Professor Wundt, upon general psychology--or, in this particular case, upon the author's system of physiological psychology--will be apparent. It should not be overlooked, however, that the examination of the mental processes that underlie the various forms in which social experience comes to expression involves a procedure which supplements, in an important way, the traditional psychological methods. More than this. Wundt's _Völkerpsychologie_ is the result of a conviction that there are certain mental phenomena which may not be interpreted satisfactorily by any psychology which restricts itself to the standpoint of individual consciousness. Fundamental to the conclusions of the present volume, therefore, is the assumption of the reality of collective minds. For Professor Wundt, however, this assumption is not in the least of a dogmatic character. On the contrary, its acceptance is necessitated by the failure of opposing theories, and its validity is sustained by the fact that it renders intelligible a large and important body of facts. If this be admitted, it follows that folk psychology supplements not merely the methods of individual or physiological psychology, but also its principles and its laws. As yet, however, the prevailing tendency of psychologists, both in England and in America, is to retain the point of view of individual consciousness even when dealing with those phenomena which Wundt considers to be creations of the social group. That this occurs so frequently without any apparent thought of the