It will be noticed that every single chapter, except the first, falls naturally into four parts; (1) the introduction, (2) the materials, (3) investigations and problems, and (4) bibliography. The first two parts of each chapter are intended to raise questions rather than to answer them. The last two, on the other hand, should outline or suggest problems for further study. The bibliographies have been selected mainly to exhibit the recognized points of view with regard to the questions raised, and to suggest the practical problems that grow out of, and are related to, the subject of the chapter as a whole. The bibliographies, which accompany the chapters, it needs to be said, are intended to be representative rather than authoritative or complete. An attempt has been made to bring together literature that would exhibit the range, the divergence, the distinctive character of the writings and points of view upon a single topic. The results are naturally subject to criticism and revision. A word should be said in regard to chapter i. It seemed necessary and important, in view of the general vagueness and uncertainty in regard to the place of sociology among the sciences and its relation to the other social sciences, particularly to history, to state somewhere, clearly and definitely, what, from the point of view of this volume, sociology is. This resulted finally in the imposition of a rather formidable essay upon what is in other respects, we trust, a relatively concrete and intelligible book. Under these circumstances we suggest that, unless the reader is specially interested in the matter, he begin with the chapter on "Human Nature," and read the first chapter last. The editors desire to express their indebtedness to Dr. W. I. Thomas for the point of view and the scheme of organization of materials which have been largely adopted in this book.[1] They are also under obligations to their colleagues, Professor Albion W. Small, Professor Ellsworth Faris, and Professor Leon C. Marshall, for constant stimulus, encouragement, and assistance. They wish to acknowledge the co-operation and the courtesy of their publishers, all the more appreciated because of the difficult technical task involved in the preparation of this volume. In preparing copy for publication and in reading proof, invaluable service was rendered by Miss Roberta Burgess.